Internet DRAFT - draft-bierman-netconf-yang-api
draft-bierman-netconf-yang-api
Network Working Group A. Bierman
Internet-Draft YumaWorks
Intended status: Standards Track M. Bjorklund
Expires: June 3, 2013 Tail-f Systems
November 30, 2012
YANG-API Protocol
draft-bierman-netconf-yang-api-01
Abstract
This document describes a RESTful protocol that provides a
programmatic interface over HTTP for accessing data defined in YANG,
using the datastores defined in NETCONF.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 3, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Simple Subset of NETCONF Functionality . . . . . . . . . . 4
1.2. Data Model Driven API . . . . . . . . . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1. NETCONF . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3. YANG . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.4. Terms . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1. Resource URI Map . . . . . . . . . . . . . . . . . . . 9
1.4.2. YANG-API Message Examples . . . . . . . . . . . . . . 9
2. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1. Message Model . . . . . . . . . . . . . . . . . . . . . . 15
2.2. Resource Model . . . . . . . . . . . . . . . . . . . . . . 15
2.2.1. YANG-API Resource Types . . . . . . . . . . . . . . . 15
2.2.2. Resource Discovery . . . . . . . . . . . . . . . . . . 16
2.3. Datastore Model . . . . . . . . . . . . . . . . . . . . . 16
2.3.1. Content Model . . . . . . . . . . . . . . . . . . . . 17
2.3.2. Editing Model . . . . . . . . . . . . . . . . . . . . 17
2.3.3. Locking Model . . . . . . . . . . . . . . . . . . . . 19
2.3.4. Persistence Model . . . . . . . . . . . . . . . . . . 19
2.3.5. Defaults Model . . . . . . . . . . . . . . . . . . . . 19
2.4. Transaction Model . . . . . . . . . . . . . . . . . . . . 20
2.5. Extensibility Model . . . . . . . . . . . . . . . . . . . 20
2.6. Versioning Model . . . . . . . . . . . . . . . . . . . . . 20
2.7. Retrieval Filtering Model . . . . . . . . . . . . . . . . 21
2.8. Access Control Model . . . . . . . . . . . . . . . . . . . 21
3. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.5. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.6. PATCH . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.8. Query Parameters . . . . . . . . . . . . . . . . . . . . . 28
3.8.1. "config" Parameter . . . . . . . . . . . . . . . . . . 28
3.8.2. "depth" Parameter . . . . . . . . . . . . . . . . . . 29
3.8.3. "format" Parameter . . . . . . . . . . . . . . . . . . 30
3.8.4. "insert" Parameter . . . . . . . . . . . . . . . . . . 30
3.8.5. "point" Parameter . . . . . . . . . . . . . . . . . . 31
3.8.6. "select" Parameter . . . . . . . . . . . . . . . . . . 32
3.9. Protocol Operations . . . . . . . . . . . . . . . . . . . 32
4. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.1. Request URI Structure . . . . . . . . . . . . . . . . . . 34
4.2. Message Headers . . . . . . . . . . . . . . . . . . . . . 35
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4.3. Message Encoding . . . . . . . . . . . . . . . . . . . . . 36
4.4. Return Status . . . . . . . . . . . . . . . . . . . . . . 36
4.5. Message Caching . . . . . . . . . . . . . . . . . . . . . 37
5. Resources . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.1. API Resource (/yang-api) . . . . . . . . . . . . . . . . . 38
5.1.1. /yang-api/datastore . . . . . . . . . . . . . . . . . 38
5.1.2. /yang-api/modules . . . . . . . . . . . . . . . . . . 38
5.1.3. /yang-api/operations . . . . . . . . . . . . . . . . . 38
5.1.4. /yang-api/version . . . . . . . . . . . . . . . . . . 40
5.2. Datastore Resource . . . . . . . . . . . . . . . . . . . . 41
5.3. Data Resource . . . . . . . . . . . . . . . . . . . . . . 41
5.3.1. Encoding YANG Instance Identifiers in the Request
URI . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.3.2. Identifying YANG-defined Data Resources . . . . . . . 44
5.3.3. Identifying Optional Keys . . . . . . . . . . . . . . 45
5.3.4. Data Resource Retrieval . . . . . . . . . . . . . . . 45
5.4. Operation Resource . . . . . . . . . . . . . . . . . . . . 47
5.4.1. Encoding Operation Input Parameters . . . . . . . . . 48
5.4.2. Encoding Operation Output Parameters . . . . . . . . . 49
5.4.3. Identifying YANG-defined Operation Resources . . . . . 50
6. Error Reporting . . . . . . . . . . . . . . . . . . . . . . . 51
6.1. Error Response Message . . . . . . . . . . . . . . . . . . 52
7. RelaxNG Grammar . . . . . . . . . . . . . . . . . . . . . . . 55
8. YANG-API module . . . . . . . . . . . . . . . . . . . . . . . 56
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 58
10. Security Considerations . . . . . . . . . . . . . . . . . . . 59
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 60
11.1. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 60
12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 61
13. Example YANG Module . . . . . . . . . . . . . . . . . . . . . 63
14. Normative References . . . . . . . . . . . . . . . . . . . . . 67
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 68
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1. Introduction
There is a need for standard mechanisms to allow WEB applications to
access the configuration data, operational data, and data-model
specific protocol operations within a networking device, in a modular
and extensible manner.
This document describes a RESTful protocol called YANG-API, running
over HTTP [RFC2616], for accessing data defined in YANG [RFC6020],
using datastores defined in NETCONF [RFC6241].
The NETCONF protocol defines configuration datastores and a set of
Create, Retrieve, Update, Delete (CRUD) operations that can be used
to access these datastores. The YANG language defines the syntax and
semantics of datastore content and operational data. RESTful
operations are used to access the hierarchical data within a
datastore.
A RESTful API can be created that provides CRUD operations on a
NETCONF datastore containing YANG-defined data. This can be done in
a simplified manner, compatible with HTTP and RESTful design
principles. Since NETCONF protocol operations are not relevant, the
user should not need any prior knowledge of NETCONF in order to use
the RESTful API.
Configuration data and state data are exposed as resources that can
be retrieved with the GET method. Resources representing
configuration data can be modified with the DELETE, PATCH, POST, and
PUT methods. Data-model specific protocol operations defined with
the YANG "rpc" statement can be invoked with the POST method.
1.1. Simple Subset of NETCONF Functionality
The framework and meta-model used for a RESTful API does not need to
mirror those used by the NETCONF protocol. It just needs to be
compatible with NETCONF. A simplified framework and protocol is
needed that utilizes the three NETCONF datastores (candidate,
running, startup), but hides the complexity of multiple datastores
from the client.
A simplified transaction model is needed that allows basic CRUD
operations on a hierarchy of conceptual resources. This represents a
limited subset of the transaction capabilities of the NETCONF
protocol.
Applications that require more complex transaction capabilities might
consider NETCONF instead of YANG-API. The following transaction
features are not provided in YANG-API:
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o datastore locking (full or partial)
o candidate datastore
o validate operation
o confirmed-commit procedure
The RESTful API is not intended to replace NETCONF, but rather
provide an additional simplified interface that follows RESTful
principles and is compatible with a resource-oriented device
abstraction. It is expected that applications that need the full
feature set of NETCONF such as notifications will continue to use
NETCONF.
The following figure shows the system components:
+-----------+ +-----------------+
| WEB app | <-------> | |
+-----------+ HTTP | network device |
| |
+-----------+ | +-----------+ |
| NMS app | <-------> | | datastore | |
+-----------+ NETCONF | +-----------+ |
+-----------------+
1.2. Data Model Driven API
YANG-API combines the simplicity of a RESTful API over HTTP with the
predictability and automation potential of a schema-driven API.
A RESTful client using YANG-API will not use any data modelling
language to define the application-specific content of the API. The
client would discover each new child resource as it traverses the
URIs return as Location IDs to discover the server capabilities.
This approach has 3 significant weaknesses wrt/ control of complex
networking devices:
o inefficient performance: configuration APIs will be quite complex
and may require thousands of protocol messages to discover all the
schema information. Typically the data type information has to be
passed in the protocol messages, which is also wasteful overhead.
o no data model richness: without a data model, the schema-level
semantics and validation constraints are not available to the
application. Data model modules such as YANG modules serve as an
"API contract" that will be honored by the server. An application
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designer can code to the data model, knowing in advance important
details about the exact protocol operations and datastore content
a conforming server implementation will support.
o no tool automation: API automation tools need some sort of content
schema to function. Such tools can automate various programming
and documentation tasks related to specific data models.
YANG-API provides the YANG module capability information supported by
the server, in case the client wants to use it. The URIs for custom
protocol operations and datastore content are predictable, based on
the YANG module definitions. Note that the YANG modules and
predictable URIs are optional to use by the client. They can be
completely ignored without any loss of protocol functionality.
Operational experience with CLI and SNMP indicates that operators
learn the 'location' of specific service or device related data and
do not expect such information to be arbitrary and discovered each
time the client opens a management session to a server.
1.3. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14, [RFC2119].
1.3.1. NETCONF
The following terms are defined in [RFC6241]:
o candidate configuration datastore
o client
o configuration data
o datastore
o configuration datastore
o protocol operation
o running configuration datastore
o server
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o startup configuration datastore
o state data
o user
1.3.2. HTTP
The following terms are defined in [RFC2616]:
o entity tag
o fragment
o header line
o message body
o method
o path
o query
o request URI
o response body
1.3.3. YANG
The following terms are defined in [RFC6020]:
o container
o data node
o key leaf
o leaf
o leaf-list
o list
o presence container (or P-container)
o RPC operation (now called protocol operation)
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o non-presence container (or NP-container)
o ordered-by system
o ordered-by user
1.3.4. Terms
The following terms are used within this document:
o API resource: a resource with the media type "application/
vnd.yang.api+xml" or ""application/vnd.yang.api+json".
o data resource: a resource with the media type "application/
vnd.yang.data+xml" or "application/vnd.yang.data+json".
o datastore resource: a resource with the media type "application/
vnd.yang.datastore+xml" or "application/vnd.yang.datastore+json"
o edit operation: a YANG-API operation on a data resource using the
POST, PUT, PATCH, or DELETE method.
o operation: the conceptual YANG-API operation for a message,
derived from the method, request URI, headers, and message body.
o operation resource: a resource with the media type
"vnd.yang.operation+xml" or "vnd.yang.operation+json"
o optional key: a key leaf for a YANG list data node, which MAY be
omitted by the client when an instance of the list is created.
o query parameter: a parameter (and its value if any), encoded
within the query portion of the request URI.
o resource: a conceptual object representing a manageable component
within a device.
o retrieval request: an operation using the GET or HEAD methods.
o target resource: the resource that is associated with a particular
message, identified by the "path" component of the request URI.
1.4. Overview
This document defines the YANG-API protocol, a RESTful API for
accessing conceptual datastores containing data defined with YANG
language. YANG-API provides an application framework and meta-model,
using HTTP operations.
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The YANG-API resources are accessed via a set of URIs defined in this
document. The set of YANG modules supported by the server will
determine the additional data model specific operations and top-level
data node resources available on the server.
1.4.1. Resource URI Map
The URI hierarchy for the YANG-API resources consists of an entry
point and up to 4 top-level resources and/or fields. Refer to
Section 5 for details on each URI.
/yang-api
/datastore
/<top-level-data-nodes> (config=true or false)
/modules
/module
/operations
/<custom protocol operations>
/version
1.4.2. YANG-API Message Examples
The examples within this document use the non-normative example YANG
module defined in Section 13.
This section shows some typical YANG-API message exchanges.
1.4.2.1. Retrieve the Top-level API Resource
By default, when a resource is retrieved, all of its fields are
returned, but none (if any) of the nested resources are returned.
Also, the default encoding is JSON. Data resources are encoded
according to the encoding rules in [I-D.lhotka-netmod-json].
The client starts by retrieving the top-level API resource, using the
entry point URI "/yang-api".
GET /yang-api HTTP/1.1
Host: example.com
The server might respond as follows. The "module" lines below are
split for display purposes only:
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HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Content-Type: application/vnd.yang.api+json
{
"yang-api": {
"modules": {
"module": [
"urn:ietf:params:xml:ns:yang:ietf-yang-api
?module=ietf-yang-api&revision=2012-05-27",
"example.com?module=example-jukebox
&revision=2012-05-30"
]
},
"version": "1.0"
}
}
To request that the response content to be encoded in XML, the
"Accept" header can be used, as in this example request:
GET /yang-api HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+xml
An alternate approach is provided using the "format" query parameter,
as in this example request:
GET /yang-api?format=xml HTTP/1.1
Host: example.com
The server will return the same response either way, which might be
as follows :
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.api+xml
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<yang-api>
<modules> <!-- wrapped for display only -->
<module>urn:ietf:params:xml:ns:yang:ietf-yang-api
?module=ietf-yang-api
&revision=2012-05-27</module>
<module>example.com?module=example-jukebox
&revision=2012-05-30</module>
</modules>
<version>1.0</version>
</yang-api>
Refer to Section 3.3 for details on the GET operation.
1.4.2.2. Create New Data Resources
To create a new "jukebox" resource, the client might send:
POST /yang-api/datastore/jukebox HTTP/1.1
Host: example.com
If the resource is created, the server might respond:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Location: http://example.com/yang-api/datastore/jukebox
Last-Modified: Mon, 23 Apr 2012 17:01:00 GMT
ETag: b3a3e673be2
To create a new "artist" resource within the "jukebox" resource, the
client might send the following request, Note that the arbitrary
integer "index" is not provided, since it is an optional key:
POST /yang-api/datastore/jukebox/artist HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"artist" : {
"name" : "The Foo Fighters"
}
}
If the resource is created, the server might respond:
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HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Location: http://example.com/yang-api/datastore/jukebox/artist/1
Last-Modified: Mon, 23 Apr 2012 17:02:00 GMT
ETag: b3830f23a4c
To create a new "album" resource for this artist within the "jukebox"
resource, the client might send the following request,
POST /yang-api/datastore/jukebox/artist/1/album HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:Alternative",
"year" : 2012
}
}
If the resource is created, the server might respond as follows.
Note that the "Location" header line is wrapped for display purposes
only:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:03:00 GMT
Server: example-server
Location: http://example.com/yang-api/datastore/
jukebox/artist/1/album/Wasting%20Light
Last-Modified: Mon, 23 Apr 2012 17:03:00 GMT
ETag: b8389233a4c
Refer to Section 3.4 for details on the POST operation.
1.4.2.3. Replace an Existing Data Resource
Note: replacing a resource is a fairly drastic operation. The PATCH
operation is often more appropriate.
The album sub-resource is re-added here for example purposes only.
To replace the "artist" resource contents, the client might send:
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PUT /yang-api/datastore/jukebox/artist/1 HTTP/1.1
Host: example.com
If-Match: b3830f23a4c
Content-Type: application/vnd.yang.data+json
{
"artist" : {
"name" : "Foo Fighters",
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:Alternative",
"year" : 2012
}
}
}
If the resource is updated, the server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:04:00 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:04:00 GMT
ETag: b27480aeda4c
Refer to Section 3.5 for details on the PUT operation.
1.4.2.4. Patch an Existing Data Resource
To replace just the "year" field in the "album" resource, the client
might send:
PATCH /yang-api/datastore/jukebox/artist/1/album/
Wasting%20Light/year HTTP/1.1
Host: example.com
If-Match: b8389233a4c
Content-Type: application/vnd.yang.data+json
{ "year" : 2011 }
If the resource is updated, the server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:49:30 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:49:30 GMT
ETag: b2788923da4c
Refer to Section 3.6 for details on the PATCH operation.
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1.4.2.5. Delete an Existing Data Resource
To delete a resource such as the "album" resource, the client might
send:
DELETE /yang-api/datastore/jukebox/artist/1/album/
Wasting%20Light HTTP/1.1
Host: example.com
If the resource is deleted, the server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:49:40 GMT
Server: example-server
Refer to Section 3.7 for details on the DELETE operation.
1.4.2.6. Invoke a Data Model Specific Operation
To invoke a data-model specific operation via an operation resource,
the POST operation is used. A client might send a "backup-datastore"
request as follows:
POST /yang-api/operations/backup-datastore HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:50:00 GMT
Server: example-server
Refer to Section 3.9 for details on using the POST operation with
operation resources.
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2. Framework
The YANG-API protocol defines a framework that can be used to
implement a common API for configuration management. This section
describes the components of the YANG-API framework.
2.1. Message Model
The YANG-API protocol uses HTTP entities for messages. A single HTTP
message corresponds to a single protocol operation. A message can
perform a single task on a single resource, such as retrieving a
resource or editing a resource. It cannot be used to combine
multiple tasks. The client cannot provide multiple (possibly
unrelated) edit operations within a single request, like the NETCONF
<edit-config> protocol operation.
2.2. Resource Model
The YANG-API protocol operates on a hierarchy of resources, starting
with the top-level API resource itself. Each resource represents a
manageable component within the device.
A resource can be considered a collection of conceptual data and the
set of allowed operations on that data. It can contain child nodes
that are either "fields" or other resources. The child resource
types and operations allowed on them are data-model specific.
A resource has its own media type identifier, represented by the
"Content-Type" header in the HTTP response message. A resource can
contain zero or more fields and zero or more resources. A resource
can be created and deleted independently of its parent resource, as
long as the parent resource exist.
A field is a child node defined within a resource. A field can
contain zero or more fields and zero or more resources. A field
cannot be created and deleted independently of its parent resource.
All YANG-API resources and fields are defined in this document except
datastore contents and protocol operations. These resource types are
defined with YANG data definition statements and the "rpc" statement.
A default mapping is defined to differentiate sub-resources from
fields within data resources.
2.2.1. YANG-API Resource Types
The YANG-API protocol defines some application specific media types
to identify each of the available resource types. The following
table summarizes the purpose of each resource.
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+-----------+--------------------------------+
| Resource | Media Type |
+-----------+--------------------------------+
| API | application/vnd.yang.api |
| Datastore | application/vnd.yang.datastore |
| Data | application/vnd.yang.data |
| Operation | application/vnd.yang.operation |
+-----------+--------------------------------+
YANG-API Media Types
These resources are described in Section 5.
2.2.2. Resource Discovery
A client SHOULD start by retrieving the top-level API resource, using
the entry point URI "/yang-api".
The YANG-API protocol does not include a resource discovery
mechanism. Instead, the definitions within the YANG modules
advertised by the server are used to construct a predictable
operation or data resource identifier.
The "depth" query parameter can be used to control how many
descendant levels should be included when retrieving sub-resources.
This parameter can be used with the GET operation to discover sub-
resources within a particular resource.
Refer to Section 3.8.2 for more details on the "depth" parameter.
2.3. Datastore Model
A conceptual "unified datastore" is used to simplify resource
management for the client. The YANG-API datastore is a combination
of the running configuration and any non-configuration data supported
by the device. By default only configuration data is returned by a
GET operation on the datastore contents.
The underlying NETCONF datastores can be used to implement the
unified datastore, but the server design is not limited to the exact
datastore procedures defined in NETCONF.
The "candidate" and "startup" datastores are not visible in the YANG-
API protocol. Transaction management and configuration persistence
are handled by the server and not controlled by the client.
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2.3.1. Content Model
The YANG-API protocol operates on a conceptual datastore defined with
the YANG data modeling language. The server lists each YANG module
it supports in the "/yang-api/modules/module" field in the top-level
API resource type, using the YANG module capability URI format
defined in RFC 6020.
The conceptual datastore contents and data-model-specific operations
are identified by the set of YANG module capability URIs. All YANG-
API content identified as either a data resource or an operation
resource is defined with the YANG language.
The classification of data as configuration or non-configuration is
derived from the YANG "config" statement. Data retrieval with the
GET operation can be filtered in several ways, including the "config"
parameter to retrieve configuration or non-configuration data.
The classification of data as a resource or field within a resource
is derived from the rules specified in Section 5.3.2.
Data ordering behavior is derived from the YANG "ordered-by"
statement. Editing mechanisms are provided to allow list or leaf-
list resources to be inserted or moved in the same manner as NETCONF,
and defined in YANG.
The server is not required to maintain system ordered data in any
particular persistent order. The server SHOULD maintain the same
data ordering for system ordered data until the next reboot or
termination of the server.
2.3.2. Editing Model
The YANG-API datastore editing model is simple and direct, similar to
the behavior of the ":writable-running" capability in NETCONF.
Each YANG-API edit of a datastore resource is activated upon
successful completion of the transaction. It is an implementation-
specific matter how the server accomplishes a YANG-API edit request.
For example, a server which only accepts edits through a candidate
datastore may internally edit this datastore and perform the "commit"
operation automatically.
Applications which need more control over the editing model might
consider using NETCONF instead of YANG-API.
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2.3.2.1. Edit Operation Discovery
Sometimes a server does not implement every operation for every
resource. Sometimes data model requirements cause a node to
implement a subset of the edit operations. For example, a server may
not allow modification of a particular configuration data node after
the parent resource has been created.
The OPTIONS operation can be used to identify which operations are
supported by the server for a particular resource. For example, if
the server will allow a data resource node to be created then the
POST operation will be returned in the response.
2.3.2.2. Edit Collision Detection
Two "edit collision detection" mechanisms are provided in YANG-API,
for datastore and data resources.
o timestamp: the last change time is maintained and the
"Last-Modified" and "Date" headers are returned in the response
for a retrieval request. The "If-Unmodified-Since" header can be
used in edit operation requests to cause the server to reject the
request if the resource has been modified since the specified
timestamp.
o entity tag: a unique opaque string is maintained and the "ETag"
header is returned in the response for a retrieval request. The
"If-Match" header can be used in edit operation requests to cause
the server to reject the request if the resource entity tag does
not match the specified value.
Note that the server is only required to maintain these fields for a
datastore resource, not for individual data resources.
Example:
In this example, the server just supports the mandatory datastore
last-changed timestamp. The client has previously retrieved the
"Last-Modified" header and has some value cached to provide in the
following request to replace a list entry with key value "11":
PATCH /yang-api/datastore/jukebox/artist/1/album/
Wasting%20Light/year HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
If-Unmodified-Since: Mon, 23 Apr 2012 17:01:00 GMT
Content-Type: application/vnd.yang.data+json
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{ "year" : "2011" }
In this example the datastore resource has changed since the time
specified in the "If-Unmodified-Since" header. The server might
respond:
HTTP/1.1 304 Not Modified
Date: Mon, 23 Apr 2012 19:01:00 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:45:00 GMT
ETag: b34aed893a4c
2.3.3. Locking Model
Datastore locking is not provided by YANG-API. An application that
needs to make several changes to the running configuration datastore
contents in sequence, without disturbance from other clients might
consider using the NETCONF protocol instead of YANG-API.
2.3.4. Persistence Model
Each YANG-API edit of a datastore resource is saved to non-volatile
storage in an implementation-specific matter by the server. There is
no guarantee that configuration changes are saved immediately, or
that the saved configuration is always a mirror of the running
configuration.
Applications which need more control over the persistence model might
consider using NETCONF instead of YANG-API.
2.3.5. Defaults Model
NETCONF has a rather complex defaults handling model for leafs.
YANG-API attempts to avoid this complexity by restricting the
operations that can be applied to a resource and fields within that
resource.
The GET method returns only nodes that exist, which will be
determined by the server. There is no mechanism for the client to
ask the server for the default values that would be used for any
nodes not present, but some default value is in use by the server.
(There is no
retrieval mode like "with-defaults=report-all" in NETCONF.)
If a leaf definition has a default value, and the leaf has not been
given a value yet, the server SHOULD NOT return any value for the
leaf in the response for a GET operation.
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Applications which need more control over the defaults model might
consider using NETCONF instead of YANG-API.
2.4. Transaction Model
The YANG-API protocol does not provide a complex transaction model
that allows for multiple protocol operations, or even operations on
multiple resources in one protocol operation. A very simple "one
operation one one resource" per transaction model is used instead.
Applications which need more control over the transaction model might
consider using NETCONF instead of YANG-API.
2.5. Extensibility Model
The YANG-API protocol is designed to be extensible for datastore
content and data-model specific protocol operations. New protocol
operations can be added without changing the entry point if they are
optional and do not alter any existing operations.
Separate namespaces for each YANG module are used. Content encoded
in XML will indicate the module using the "namespace" URI value in
the YANG module. Content encoded in JSON will indicate the module
using the module name specified in the YANG module. JSON encoding
rules for module namespaces are specified in
[I-D.lhotka-netmod-json].
2.6. Versioning Model
The version of a resource instance is identified with an entity tag,
as defined by HTTP. The version identifiers in this section apply to
the version of the schema definition of a resource. There are two
types of schema versioning information used in the YANG-API protocol:
o the YANG-API protocol version
o data and operation resource definition versions
The protocol version is identified by the string used for the well-
known URI entry point "/yang-api". This would be changed (e.g.,
"/yang-api2") if non-backward compatible changes are ever needed.
Minor version changes that do not break backward-compatibility will
not cause the entry point to change.
The API "yang-api/version" field can be used by the client to
identify the exact version of the YANG-API protocol implemented by
the server. This value will include the complete YANG-API protocol
version. The "/yang-api" entry point will only change (e.g.,
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"/yang-api2") if non-backward compatible changes are made to the
protocol. The "/yang-api/version" field MUST be updated every time
the protocol specification is republished.
The resource definition version for a data or operation resource is a
date string, which is the revision date of the YANG module that
defines the resource. The resource version for all other resource
types is a numeric string, defined by the "/yang-api/version" field.
2.7. Retrieval Filtering Model
There are four types of filtering for retrieval of data resources in
the YANG-API protocol.
o conditional all-or-nothing: use some conditional test mechanism in
the request headers and retrieve either a complete "200 OK"
response if the condition is met, or a "304 Not Modified" Status-
Line if the condition is not met.
o data classification: request configuration or non-configuration
data.
o subset: request a subset of all possible instances of a list or
leaf-list data resource.
o filter: request a subset of all possible descendant nodes within
the target resource. The "select" query parameter can be used for
this purpose.
Refer to Section 5.3.4 for details on data retrieval filtering.
2.8. Access Control Model
The YANG-API protocol provides no granular access control for any
content except for operation and data resources. The NETCONF Access
Control Model (NACM) is defined in [RFC6536]. There is a specific
mapping between YANG-API operations and NETCONF edit operations,
defined in Table 1. The resource path also needs to be converted
internally by the server to the corresponding YANG instance-
identifier. Using this information, the server can apply the NACM
access control rules to YANG-API messages.
The server MUST NOT allow any operation to any resources that the
client is not authorized to access.
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3. Operations
The YANG-API protocol uses HTTP methods to identify the CRUD
operation requested for a particular resource or field within a
resource. The following table shows how the YANG-API operations
relate to NETCONF protocol operations:
+----------+-------------------------------------+
| YANG-API | NETCONF |
+----------+-------------------------------------+
| OPTIONS | none |
| HEAD | none |
| GET | <get-config>, <get> |
| POST | <edit-config> (operation="create") |
| PUT | <edit-config> (operation="replace") |
| PATCH | <edit-config> (operation="merge") |
| DELETE | <edit-config> (operation="delete") |
+----------+-------------------------------------+
Table 1: CRUD Operations in YANG-API
The NETCONF "remove" operation attribute is not supported by the HTTP
DELETE method. The resource must exist or the DELETE operation will
fail.
This section defines the YANG-API protocol usage for each HTTP
method.
3.1. OPTIONS
The OPTIONS method is sent by the client to discover which methods
are supported by the server for a specific resource, or field within
a resource. It is supported for all media types. Note that
implementation of this operation is part of HTTP, and this section
does not introduce any additional requirements.
The request MUST contain a request URI that contains at least the
entry point component.
The server will return a "Status-Line" header containing "204 No
Content". and include the "Allow" header in the response. This
header will be filled in, based on the target resource media type.
Other headers MAY also be included in the response.
Example 1:
A client might request the methods supported for a data resource
called "library"
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OPTIONS /yang-api/datastore/jukebox/library HTTP/1.1
Host: example.com
The server might respond (for a config=true list):
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Allow: OPTIONS,HEAD,GET,POST,PUT,PATCH,DELETE
Example 2:
A client might request the methods supported for a non-configuration
leaf within a data resource:
OPTIONS /yang-api/datastore/jukebox/library/
song-count HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Allow: OPTIONS,HEAD,GET
Example 3:
A client might request the methods supported for an operation
resource called "play":
OPTIONS /yang-api/operations/play HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Allow: POST
3.2. HEAD
The HEAD operation is sent by the client to retrieve just the headers
that would be returned for the comparable GET operation, without the
response body. The HTTP HEAD method is used for this operation. It
is supported for all resource types, except operation resources.
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The request MUST contain a request URI that contains at least the
entry point component.
The same query parameters supported by the GET operation are
supported by the HEAD operation. For example, the "select" query
parameter can be used to specify a field within the target resource.
The access control behavior is enforced as if the method was GET
instead of HEAD. The server MUST respond the same as if the method
was GET instead of HEAD, except that no response body is included.
Example:
The client might request the response headers for the default (JSON)
representation of the "library" resource:
HEAD /yang-api/datastore/jukebox/library HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:02:40 GMT
Server: example-server
Content-Type: application/vnd.yang.data+json
Cache-Control: no-cache
Pragma: no-cache
ETag: a74eefc993a2b
Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT
3.3. GET
The GET operation is sent by the client to retrieve data and meta-
data for a resource or field within a resource. The HTTP GET method
is used for this operation. It is supported for all resource types,
except operation resources. The request MUST contain a request URI
that contains at least the entry point component.
The following query parameters are supported by the GET operation:
+--------+---------+------------------------------------------------+
| Name | Section | Description |
+--------+---------+------------------------------------------------+
| config | 3.8.1 | Request either configuration or |
| | | non-configuration data |
| depth | 3.8.2 | Control the depth of a retrieval request |
| format | 3.8.3 | Request either JSON or XML content in the |
| | | response |
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| select | 3.8.6 | Specify a field within the target resource |
+--------+---------+------------------------------------------------+
GET Query Parameters
The server MUST NOT return any data resources or fields within any
data resources for which the user does not have read privileges.
If the user is not authorized to read any portion of the target
resource, an error response containing a "403 Forbidden" Status-Line
is returned to the client.
If the user is authorized to read some but not all of the target
resource, the unauthorized content is omitted from the response
message body, and the authorized content is returned to the client.
Example:
The client might request the response headers for a JSON
representation of the "library" resource:
GET /yang-api/datastore/jukebox/library/artist/
1/album HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:02:40 GMT
Server: example-server
Content-Type: application/vnd.yang.data+json
Cache-Control: no-cache
Pragma: no-cache
ETag: a74eefc993a2b
Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT
{
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:Alternative",
"year" : 2011
}
}
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3.4. POST
The POST operation is sent by the client for various reasons. The
HTTP POST method is used for this purpose. The request MUST contain
a request URI that contains a target resource that identifies one of
the following resource types:
+-------------+--------------------------------------+
| Type | Description |
+-------------+--------------------------------------+
| Data | Create a configuration data resource |
| Operation | Invoke protocol operation |
| Transaction | Create a new transaction |
+-------------+--------------------------------------+
Resource Types that Support POST
The following query parameters are supported by the POST operation:
+--------+---------+-----------------------------------------+
| Name | Section | Description |
+--------+---------+-----------------------------------------+
| insert | 3.8.4 | Specify where to insert a resource |
| point | 3.8.5 | Specify the insert point for a resource |
+--------+---------+-----------------------------------------+
POST Query Parameters
If the POST operation succeeds, a "200 OK" Status-Line is returned if
there is no response message body, and a "204 No Content" Status-Line
is returned if there is a response message body.
If the user is not authorized to invoke the target (operation)
resource, or create the target resource, an error response containing
a "403 Forbidden" Status-Line is returned to the client. All other
error responses are handled according to the procedures defined in
Section 6.
3.5. PUT
The PUT operation is sent by the client to replace the target
resource.
The HTTP PUT method is used for this purpose. The request MUST
contain a request URI that contains a target resource that identifies
the data resource to replace.
The following query parameters are supported by the PUT operation:
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+--------+---------+---------------------------------------+
| Name | Section | Description |
+--------+---------+---------------------------------------+
| insert | 3.8.4 | Specify where to move a resource |
| point | 3.8.5 | Specify the move point for a resource |
+--------+---------+---------------------------------------+
PUT Query Parameters
If the PUT operation succeeds, a "200 OK" Status-Line is returned,
and there is no response message body.
If the user is not authorized to replace the target resource an error
response containing a "403 Forbidden" Status-Line is returned to the
client. All other error responses are handled according to the
procedures defined in Section 6.
3.6. PATCH
The PATCH operation uses the HTTP PATCH method defined in [RFC5789]
to provide a "merge" editing mode for data resources. Instead of
replacing all or part of the target resource, the supplied values are
merged into the target resource.
If the PATCH operation succeeds, a "200 OK" Status-Line is returned,
and there is no response message body.
If the user is not authorized to alter the target resource an error
response containing a "403 Forbidden" Status-Line is returned to the
client. All other error responses are handled according to the
procedures defined in Section 6.
3.7. DELETE
The DELETE operation uses the HTTP DELETE method to delete the target
resource.
If the DELETE operation succeeds, a "200 OK" Status-Line is returned,
and there is no response message body.
If the user is not authorized to delete the target resource then an
error response containing a "403 Forbidden" Status-Line is returned
to the client. All other error responses are handled according to
the procedures defined in Section 6.
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3.8. Query Parameters
Each YANG-API operation allows zero or more query parameters to be
present in the request URI. Refer to Section 3 for details on the
query parameters used in the definition of each operation.
Query parameters can be given in any order. Each parameter can
appear zero or one time. A default value may apply if the parameter
is missing.
This section defines all the YANG-API query parameters.
3.8.1. "config" Parameter
The "config" parameter is used to specify whether configuration or
non-configuration data is requested.
This parameter is only supported for the GET and HEAD methods. It is
also only supported if the target resource is a data resource.
syntax: config= true | false
default: true
Example:
This example request by the client would retrieve only the non-
configuration data nodes that exist within the second-level "library"
resource.
GET /yang-api/datastore/jukebox/library?config=false HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+xml
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:30 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.data+json
{
"library" : {
"artist-count" : 42,
"album-count" : 59,
"song-count" : 374
}
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}
3.8.2. "depth" Parameter
The "depth" parameter is used to specify the number of nest levels
returned in a response for a GET operation. A nest-level consists of
the target resource and any child nodes which are optional data nodes
(anyxml, leaf, or leaf-list). A non-presence container is
transparent when determining the nest level. A child node (which is
not a non-presence container) within a non-presence container is used
to determine the nest-level.
The start level is determined by the target resource for the
operation.
syntax: depth=<range: 1..max> | unbounded
default: 1
Example:
This example operation would retrieve 2 levels of configuration data
nodes that exist within the top-level "jukebox" resource.
GET /yang-api/datastore/jukebox?depth=2 HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:11:30 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.data+json
{
"jukebox" : {
"library" : {
"artist" : {
"index" : 1,
"name" : "Foo Fighters"
}
},
"player" : {
"gap" : 0.5
}
}
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}
3.8.3. "format" Parameter
The "format" parameter is used to specify the format of any content
returned in the response. Note that the "Accept" header MAY be used
instead of this parameter to identify the format desired in the
response. For example:
GET /yang-api/datastore/routing HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+xml
This example request would retrieve only the configuration data nodes
that exist within the top-level "routing" resource, and retrieve them
in XML encoding instead of JSON encoding.
The "format" parameter is only supported for the GET and HEAD
methods. It is supported for all YANG-API media types.
syntax: format= xml | json
default: json
Example:
GET /yang-api/datastore/routing?format=xml HTTP/1.1
Host: example.com
This example URI would retrieve only the configuration data nodes
that exist within the top-level "routing" resource, and retrieve them
in XML encoding instead of JSON encoding.
3.8.4. "insert" Parameter
The "insert" parameter is used to specify how a resource should be
inserted (or moved) within the user-ordered list or leaf-list data
resource.
This parameter is only supported for the POST and PUT methods. It is
also only supported if the target resource is a data resource, and
that data represents a YANG list or leaf-list that is ordered by the
user, not the system.
If the values "before" or "after" are used, then a "point" parameter
for the insertion parameter MUST also be present.
syntax: insert= first | last | before | after
default: last
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Example:
Request from client:
POST /yang-api/datastore/jukebox/library/artist/1/album
/Wasting%20Light/song?insert=first HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"song" : {
"name" : "Bridge Burning",
"location" : "/media/bridge_burning.mp3",
"format" : "MP3",
"length" : 286
}
}
Response from server: 201 status
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
Location: http://example.com/yang-api/datastore/jukebox
/library/artist/1/album?Wasting%20Light/song/1
ETag: eeeada438af
3.8.5. "point" Parameter
The "point" parameter is used to specify the insertion point for a
data resource that is being created or moved within a user ordered
list or leaf-list. It is ignored unless the "insert" query parameter
is also present, and has the value "before" or "after".
This parameter contains the instance identifier of the resource, or
field within a resource, to be used as the insertion point for a POST
or PUT operation. It is encoded according to the rules defined in
Section 5.3.1. There is no default for this parameter.
syntax: point= <instance-identifier of insertion point node>
Example:
In this example, the client is moving an existing "song" resource
within an "album" resource after another song. The request URI is
split for display purposes only.
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Request from client:
PUT /yang-api/datastore/jukebox/library/artist/1/album/
Wasting%20Light/song/2?insert=after
&point=/yang-api/datastore/jukebox/library/artist/1/
album/Wasting%20Light/song/4 HTTP/1.1
Host: example.com
Response from server:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
ETag: abcada438af
3.8.6. "select" Parameter
The "select" query parameter is used to specify an expression which
can represent a subset of all data nodes within the target resource.
It contains a relative path expression, using the target resource as
the context node.
It is supported for all resource types except operation resources.
The contents are encoded according to the "api-select" rule defined
in Section 5.3.1. This parameter is only allowed for GET and HEAD
operations.
[FIXME: the syntax of the select string is still TBD; XPath, schema-
identifier, regular expressions, something else]
Refer to Section 1.4.2 for example request messages using the
"select" parameter.
3.9. Protocol Operations
The YANG-API also allows data-model specific protocol operations to
be invoked using the POST method. The media type
"vnd.yang.operation+xml" or "vnd.yang.operation+json" MUST be used in
the "Content-Type" field in the message header.
Data model specific operations are supported. The syntax and
semantics of these operations exactly correspond to the YANG "rpc"
statement definition for the operation.
Any input for a protocol operation is encoded in an element called
"input", which corresponds to the <input> element in a NETCONF
message. The child nodes of the "input" element are encoded
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according to the data definition statements in the input section of
the "rpc" statement.
Any output for a protocol operation is encoded in an element called
"output", which corresponds to the <rpc-reply> element in a NETCONF
message. The child nodes of the "output" element are encoded
according to the data definition statements in the output section of
the "rpc" statement.
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4. Messages
This section describes the messages that are used in the YANG-API
protocol.
4.1. Request URI Structure
Resources are represented with URIs following the structure for
generic URIs in [RFC3986].
A YANG-API operation is derived from the HTTP method and the request
URI, using the following conceptual fields:
<OP> /yang-api/<path>?<query>#<fragment>
^ ^ ^ ^ ^
| | | | |
method entry resource query fragment
M M O O I
M=mandatory, O=optional, I=ignored
<text> replaced by client with real values
o method: the HTTP method identifying the YANG-API operation
requested by the client, to act upon the target resource specified
in the request URI. YANG-API operation details are described in
Section 3.
o entry: the well-known YANG-API entry point ("/yang-api").
o resource: the path expression identifying the resource that is
being accessed by the operation. If this field is not present,
then the target resource is the API itself, represented by the
media type "vnd.yang.api".
o query: the set of parameters associated with the YANG-API message.
These have the familiar form of "name=value" pairs. There is a
specific set of parameters defined, although the server MAY choose
to support additional parameters not defined in this document.
o fragment: This field is not used by the YANG-API protocol.
The client SHOULD NOT assume the final structure of a URI path for a
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resource. Instead, existing resources can be discovered with the GET
operation. When new resources are created by the client, a
"Location" header is returned, which identifies the path of the newly
created resource. The client MUST use this exact path identifier to
access the resource once it has been created.
The "target" of an operation is a resource. The "path" field in the
request URI represents the target resource for the operation.
4.2. Message Headers
There are several HTTP header lines utilized in YANG-API messages.
Messages are not limited to the HTTP headers listed in this section.
HTTP defines which header lines are required for particular
circumstances. Refer to each operation definition section in
Section 3 for examples on how particular headers are used.
There are some request headers that are used within YANG-API, usually
applied to data resources. The following tables summarize the
headers most relevant in YANG-API message requests:
+---------------------+---------------------------------------------+
| Name | Description |
+---------------------+---------------------------------------------+
| Accept | Response Content-Types that are acceptable |
| Content-Type | The media type of the request body |
| Host | The host address of the server |
| If-Match | Only perform the action if the entity |
| | matches ETag |
| If-Modified-Since | Only perform the action if modified since |
| | time |
| If-Range | Only retrieve range if resource unchanged |
| If-Unmodified-Since | Only perform the action if un-modified |
| | since time |
| Range | Specify a range of data resource entries |
+---------------------+---------------------------------------------+
YANG-API Request Headers
The following tables summarize the headers most relevant in YANG-API
message responses:
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+---------------+---------------------------------------------------+
| Name | Description |
+---------------+---------------------------------------------------+
| Allow | Valid actions when 405 error returned |
| Content-Type | The media type of the response body |
| Date | The date and time the message was sent |
| ETag | An identifier for a specific version of a |
| | resource |
| Last-Modified | The last modified date and time of a resource |
| Location | The resource identifier for a newly created |
| | resource |
+---------------+---------------------------------------------------+
YANG-API Response Headers
4.3. Message Encoding
YANG-API messages are encoded in HTTP according to RFC 2616. The
"utf-8" character set is used for all messages. YANG-API message
content is sent in the HTTP message body.
Content is encoded in either JSON or XML format.
XML encoding rules for data nodes are defined in [RFC6020]. The same
encoding rules are used for all XML content. XML attributes are not
used and will be ignored if present in an XML-encoded message.
JSON encoding rules are defined in [I-D.lhotka-netmod-json]. Special
encoding rules are needed to handle multiple module namespaces and
provide consistent data type processing.
Request input content encoding format is identified with the Content-
Type header. This field MUST be present if message input is sent by
the client.
Response output content encoding format is identified with the Accept
header, the "format" query parameter, or if neither is specified, the
request input encoding format is used. If there was no request
input, then the default output encoding is JSON. File extensions
encoded in the request are not used to identify format encoding.
4.4. Return Status
Each message represents some sort of resource access. An HTTP
"Status-Line" header line is returned for each request. If a 4xx or
5xx range status code is returned in the Status-Line, then the error
information will be returned in the response, according to the format
defined in Section 6.1.
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4.5. Message Caching
Since the datastore contents change at unpredictable times, responses
from a YANG-API server generally SHOULD NOT be cached.
The server SHOULD include a "Cache-Control" header in every response
that specifies whether the response should be cached. A "Pragma"
header specifying "no-cache" MAY also be sent in case the
"Cache-Control" header is not supported.
Instead of using HTTP caching, the client SHOULD track the "ETag"
and/or "Last-Modified" headers returned by the server for the
datastore resource (or data resource if the server supports it).
A retrieval request for a resource can include headers such as
"If-None-Match" or "If-Modified-Since" which will cause the server to
return a "304 Not Modified" Status-Line if the resource has not
changed.
The client MAY use the HEAD operation to retrieve just the message
headers, which SHOULD include the "ETag" and "Last-Modified" headers,
if this meta-data is maintained for the target resource.
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5. Resources
The resources used in the YANG-API protocol are identified by the
"path" component in the request URI. Each operation is performed on
a target resource.
5.1. API Resource (/yang-api)
The API resource contains the state and access points for the YANG-
API features.
It is the top-level resource and has the media type "application/
vnd.yang.api+xml" or "application/vnd.yang.api+json". It is
accessible through the well-known URI "/yang-api".
This resource has the following fields:
+------------+--------------------------------+
| Field Name | Description |
+------------+--------------------------------+
| datastore | Link to "datastore" resource |
| modules | YANG module capability URIs |
| operations | Data-model specific operations |
+------------+--------------------------------+
YANG-API Resource Fields
5.1.1. /yang-api/datastore
This mandatory resource represents the running configuration
datastore and any non-configuration data available. It may be
retrieved and edited directly. It cannot be created or deleted by
the client. This resource type is defined in Section 5.2.
5.1.2. /yang-api/modules
This mandatory field contains the identifiers for the YANG data model
modules supported by the server. There MUST be exactly one instance
of this field.
The server MUST maintain a last-modified timestamp for this field,
and return the "Last-Modified" header when this field is retrieved
with the GET or HEAD methods.
5.1.3. /yang-api/operations
This optional field provides access to the data-model specific
protocol operations supported by the server. The server MAY omit
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this field if no data-model specific operations are advertised.
Any data-model specific operations defined in the YANG modules
advertised by the server SHOULD be available as child nodes of this
field.
5.1.3.1. /yang-api/modules/module
This mandatory field contains one URI string for each YANG data model
module supported by the server. There MUST be an instance of this
field for every YANG module that is accessible via an operation
resource or a data resource.
The server MAY maintain a last-modified timestamp for each instance
of this resource, and return the "Last-Modified" header when this
resource is retrieved with the GET or HEAD methods. If not supported
then the timestamp for the parent "modules" field MUST NOT be used
instead.
The contents of this field are encoded with the "uri" derived type
from the "ietf-iana-types" modules in [RFC6021].
There are additional encoding requirements for this field. The URI
MUST follow the YANG module capability URI formatting defined in
section 5.6.4 of [RFC6020].
5.1.3.2. Retrieval Example
In this example the client is retrieving the modules field from the
server in the default JSON format:
GET /yang-api?select=modules HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond as follows. Note that the content below is
split across multiple lines for display purposes only:
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HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
Content-Type: application/vnd.yang.api+json
{
"yang-api": {
"modules": {
"module": [
"example.com?module=foo&revision=2012-01-02",
"example.com?module=bar&revision=2011-10-10"
"example.com?module=itf&revision=2011-10-10
&feature=restore"
]
}
}
}
5.1.4. /yang-api/version
This mandatory field identifies the specific version of the YANG-API
protocol implemented by the server.
The same server-wide response MUST be returned each time this field
is retrieved. It is assigned by the server when the server is
started. The server MUST return the value "1.0" for this version of
the YANG-API protocol.
This field is encoded with the rules for an "enumeration" data type,
using the following leaf definition:
leaf version {
config false;
type enum {
enum "1.0" {
description
"Version 1.0 of the YANG-API protocol.";
}
}
}
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5.2. Datastore Resource
A datastore resource represents the conceptual root of a tree of data
resources.
The server MUST maintain a last-modified timestamp for this resource,
and return the "Last-Modified" header when this resource is retrieved
with the GET or HEAD methods. Only changes to configuration data
resources within the datastore affect this timestamp.
The server SHOULD maintain a resource entity tag for this resource,
and return the "ETag" header when this resource is retrieved with the
GET or HEAD methods. The resource entity tag SHOULD be changed to a
new previously unused value if changes to any configuration data
resources within the datastore are made.
A datastore resource can be retrieved with the GET operation, to
retrieve either configuration data resources or non-configuration
data resources within the datastore. The "config" query parameter is
used to choose between them. Refer to Section 3.8.1 for more
details.
The depth of the subtrees returned in retrieval operations can be
controlled with the "depth" query parameter. The number of nest
levels, starting at the target resource, can be specified, or an
unlimited number can be returned. Refer to Section 3.8.2 for more
details.
A datastore resource cannot be written directly with any edit
operation. Only the configuration data resources within the
datastore resource can be edited.
5.3. Data Resource
A data resource represents a YANG data node that is a descendant node
of a datastore resource.
For configuration data resources, the server MAY maintain a last-
modified timestamp for the resource, and return the "Last-Modified"
header when it is retrieved with the GET or HEAD methods.
For configuration data resources, the server MAY maintain a resource
entity tag for the resource, and return the "ETag" header when it is
retrieved as the target resource with the GET or HEAD methods. The
resource entity tag SHOULD be changed to a new previously unused
value if changes to the resource or any configuration field within
the resource is altered.
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A data resource can be retrieved with the GET operation, to retrieve
either configuration data resources or non-configuration data
resources within the target resource. The "config" query parameter
is used to choose between them. Refer to Section 3.8.1 for more
details.
The depth of the subtrees returned in retrieval operations can be
controlled with the "depth" query parameter. The number of nest
levels, starting at the target resource, can be specified, or an
unlimited number can be returned. Refer to Section 3.8.2 for more
details.
A configuration data resource can be altered by the client with some
of all of the edit operations, depending on the target resource and
the specific operation. Refer to Section 3 for more details on edit
operations.
5.3.1. Encoding YANG Instance Identifiers in the Request URI
In YANG, data nodes are named with an absolute XPath expression, from
the document root to the target resource. In YANG-API, URL friendly
path expressions are used instead.
The YANG "instance-identifier" (i-i) data type is represented in
YANG-API with the path expression format defined in this section.
+-------+-------------------------------------------+
| Name | Comments |
+-------+-------------------------------------------+
| point | Insertion point is always a full i-i |
| path | Request URI path is a full or partial i-i |
+-------+-------------------------------------------+
YANG-API instance-identifier Type Conversion
The "path" component of the request URI contains the absolute path
expression that identifies the target resource. The "select" query
parameter is used to optionally identify the requested data nodes
within the target resource to be retrieved in a GET operation.
A predictable location for a data resource is important, since
applications will code to the YANG data model module, which uses
static naming and defines an absolute path location for all data
nodes.
A YANG-API data resource identifier is not an XPath expression. It
is encoded from left to right, starting with the top-level data node,
according to the "api-path" rule in Section 5.3.1.1. The node name
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of each ancestor of the target resource node is encoded in order,
ending with the node name for the target resource.
If the "select" is present, it is encoded, starting with a child node
of the target resource, according to the "api-select" rule defined in
Section 5.3.1.1.
If a data node in the path expression is a YANG list node, then the
key values for the list (if any) are encoded according to the
"key-value" rule. If the list node is the target resource, then the
key values MAY be omitted, according to the operation. For example,
the POST operation to create a new data resource for a list node does
not allow the key values to be present in the request URI.
The key leaf values for a data resource representing a YANG list MUST
be encoded as follows:
o The value of each leaf identified in the "key" statement is
encoded in order.
o All the components in the "key" statement MUST be encoded.
Partial instance identifiers are not supported.
o Each value is encoded using the "key-value" rule in
Section 5.3.1.1, according to the encoding rules for the data type
of the key leaf.
o An empty string can be a valid key value (e.g., "/top/list/key1//
key3").
o The "/" character MUST be URL-encoded (i.e., "%2F").
o All whitespace MUST be URL-encoded.
o A "null" value is not allowed since the "empty" data type is not
allowed for key leafs.
o The XML encoding is defined in [RFC6020].
o The JSON encoding is defined in [I-D.lhotka-netmod-json].
o The entire "key-value" MUST be properly URL-encoded, according to
the rules defined in [RFC3986].
Notifications are not supported by YANG-API because they are not
supported by HTTP. YANG notification statements are ignored by a
YANG-API server.
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Examples:
/yang-api/datastore/jukebox/library/artist/17&select=name
/yang-api/datastore/newlist/17&select=nextlist/22/44/myleaf
/yang-api/datastore/somelist/fred%20and%20wilma
/yang-api/datastore/somelist/fred%20and%20wilma/address
5.3.1.1. ABNF For Data Resource Identifiers
The following ABNF syntax is used to construct YANG-API path
identifiers:
api-path = "/" api-identifier
0*("/" (api-identifier | key-value ))
[FIXME: the syntax for the select string is still TBD]
api-select = api-identifier
0*("/" (api-identifier | key-value ))
api-identifier = [module-name ":"] identifier
module-name = identifier
key-value = string
;; An identifier MUST NOT start with
;; (('X'|'x') ('M'|'m') ('L'|'l'))
identifier = (ALPHA / "_")
*(ALPHA / DIGIT / "_" / "-" / ".")
string = <an unquoted string>
5.3.2. Identifying YANG-defined Data Resources
The data resources used in YANG-API are defined with YANG data
definition statements.
Not every data node defined in a YANG module should be treated as a
resource. The YANG-API needs to know which YANG data nodes are
resources, and which are fields within a resource.
For data resources, YANG-API uses a simple algorithm for defining
resource boundaries, within the conceptual sub-trees described by
YANG data definition statements.
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All top-level data nodes are considered to be resources. For nodes
within a top-level resource:
o a presence container starts a new resource
o a list starts a new resource
o an optional terminal node (anyxml, leaf, or leaf-list) starts a
new resource
o a data node of type "anyxml" cannot have any sub-resources
A non-configuration data node cannot be a separate resource from its
parent. Only top-level data nodes are considered to be resources
(which only support retrieval methods).
5.3.3. Identifying Optional Keys
It is sometimes useful to have the server assign the key(s) for a new
resource. The "Location" header will indicate the key value(s) that
the server selected, so the client does not need to provide all the
key leaf values.
It is useful to identify in the YANG data model module which key
leafs are optional to provide, and which are not. The YANG extension
statement "optional-key" is provided to indicate that the leaf
definition represents an optional key.
The client MAY provide a value for a key leaf in a POST operation.
Refer to Section 8 for details on the "optional-key" extension.
Refer to Section 13 for usage examples of this YANG extension
statement.
5.3.4. Data Resource Retrieval
There are four types of filtering for retrieval of data resources.
This section defines each mode.
5.3.4.1. Conditional Retrieval
The HTTP headers (such as "If-Modified-Since" and "If-Match") can by
used in for a request message for a GET operation to check a
condition within the server state, such as the last time the
datastore resource was modified, or the resource entity tag of the
target resource.
If the condition is met according to the header definition, a "200
OK" Status-Line and the data requested is returned in the response
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message. If the condition is not met, a "304 Not Modified" Status-
Line is returned in response message instead.
5.3.4.2. Data Classification Retrieval
The "config" query parameter can be used with the GET operation to
specify whether configuration or non-configuration data is requested.
Refer to Section 3.8.1 for more details on the "config" query
parameter.
5.3.4.3. Subset Retrieval
The "Range" header is used to request a specific subset of the
instances of a list or leaf-list data resource that are returned by
the server for a retrieval operation. Normally, if the target
resource in a request message does not specify an instance, then all
instances are returned.
The YANG-API protocol uses the token "entries" instead of "bytes" as
the range units.
The entries are numbered starting from "0". A list or leaf-list can
change order between requests so the client needs to be aware of the
data model semantics, and whether the list contents are stable enough
to use the subset retrieval mechanism.
If the requested range cannot be returned because the range
specification includes index values for entries that do not exist,
then an error occurs, and the server MUST return a "416 Requested
range not satisfiable" Status-Line.
If the range request can be satisfied, then a "200 OK" Status-Line is
returned, and the response MUST include a "Content-Range" header
indicating which entries are returned. The response message body
contains the data for the requested range of entries.
Example:
In this example, the client is requesting 5 "artist" resource
entries, starting with the 10th entry:
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Request from client:
GET /yang-api/datastore/jukebox/library/artist HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
Range: entries 10-14
Response from server:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 13:01:20 GMT
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.data+json
Content-Range: entries 10-14
Server: example-server
Last-Modified: Mon, 23 Apr 2012 02:12:20 GMT
ETag: abcada438af
{
"artist" : {
// content removed for brevity
}
}
5.3.4.4. Filtered Retrieval
The "select" query parameter is used to specify a filter that should
be applied to the target resource to request a subset of all possible
descendant nodes within the target resource.
The format of the "select" parameter string is defined in
Section 3.8.6. The set of nodes selected by the filter expression is
applied to each context node identified by the target resource.
5.4. Operation Resource
An operation resource represents an protocol operation defined with
the YANG "rpc" statement.
All operation resources share the same module namespace as any top-
level data resources, so the name of an operation resource cannot
conflict with the name of a top-level data resource defined within
the same module.
If 2 different YANG modules define the same "rpc" identifier, then
the module name MUST be used in the request URI. For example, if
"module-A" and "module-B" both defined a "reset" operation, then
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invoking the operation from "module-A" would be requested as follows:
POST /yang-api/operations/module-A:reset HTTP/1.1
Server example.com
Any usage of an operation resource from the same module, with the
same name, refers to the same "rpc" statement definition. This
behavior can be used to design protocol operations that perform the
same general function on different resource types.
If the "rpc" statement has an "input" section, then a message body
MAY be sent by the client in the request, otherwise the request
message MUST NOT include a message body. If the "rpc" statement has
an "output" section, then a message body MAY be sent by the server in
the response. Otherwise the server MUST NOT include a message body
in the response message, and MUST send a "204 No Content" Status-Line
instead.
5.4.1. Encoding Operation Input Parameters
If the "rpc" statement has an "input" section, then the "input" node
is provided in the message body, corresponding to the YANG data
definition statements within the "input" section.
Example:
The following YANG definition is used for the examples in this
section.
rpc reboot {
input {
leaf delay {
units seconds;
type uint32;
default 0;
}
leaf message { type string; }
leaf language { type string; }
}
}
The client might send the following POST request message:
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POST /yang-api/datastore/operations/reboot HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"input" : {
"delay" : 600,
"message" : "Going down for system maintenance",
"language" : "en-US"
}
}
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 25 Apr 2012 11:01:00 GMT
Server: example-server
5.4.2. Encoding Operation Output Parameters
If the "rpc" statement has an "output" section, then the "output"
node is provided in the message body, corresponding to the YANG data
definition statements within the "output" section.
Example:
The following YANG definition is used for the examples in this
section.
rpc get-reboot-info {
input {
leaf reboot-time {
units seconds;
type uint32;
}
leaf message { type string; }
leaf language { type string; }
}
}
The client might send the following POST request message:
POST /yang-api/datastore/operations/get-reboot-info HTTP/1.1
Host: example.com
The server might respond:
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HTTP/1.1 200 OK
Date: Mon, 25 Apr 2012 11:10:30 GMT
Server: example-server
Content-Type: application/vnd.yang.data+json
{
"output" : {
"reboot-time" : 30,
"message" : "Going down for system maintenance",
"language" : "en-US"
}
}
5.4.3. Identifying YANG-defined Operation Resources
The operation resources used in YANG-API are defined with YANG "rpc"
statements. All "rpc" statements within a YANG module that are
supported by the server are available as operation resources.
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6. Error Reporting
HTTP Status-Lines are used to report success or failure for YANG-API
operations. The <rpc-error> element returned in NETCONF error
responses contains some useful information. This error information
is adapted for use in YANG-API, and error information is returned for
"4xx" class of status codes.
The following table summarizes the return status codes used
specifically by YANG-API operations:
+-------------------------------+-----------------------------------+
| Status-Line | Description |
+-------------------------------+-----------------------------------+
| 100 Continue | POST accepted, 201 should follow |
| 200 OK | Success with response body |
| 201 Created | POST to create a resource success |
| 202 Accepted | POST to create a resource |
| | accepted |
| 204 No Content | Success without response body |
| 304 Not Modified | Conditional operation not done |
| 400 Bad Request | Invalid request message |
| 403 Forbidden | Access to resource denied |
| 404 Not Found | Resource target or resource node |
| | not found |
| 405 Method Not Allowed | Method not allowed for target |
| | resource |
| 409 Conflict | Resource or lock in use |
| 413 Request Entity Too Large | too-big error |
| 414 Request-URI Too Large | too-big error |
| 415 Unsupported Media Type | non YANG-API media type |
| 416 Requested range not | If-Range error |
| satisfiable | |
| 500 Internal Server Error | operation-failed |
| 501 Not Implemented | unknown-operation |
| 503 Service Unavailable | Recoverable server error |
+-------------------------------+-----------------------------------+
HTTP Status Codes used in YANG-API
Since an operation resource is defined with a YANG "rpc" statement, a
mapping between the NETCONF <error-tag> value and the HTTP status
code is needed. The specific error condition and response code to
use are data-model specific and might be contained in the YANG
"description" statement for the "rpc" statement.
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+-------------------------+-------------+
| <error-tag> | status code |
+-------------------------+-------------+
| in-use | 409 |
| invalid-value | 400 |
| too-big | 413 |
| missing-attribute | 400 |
| bad-attribute | 400 |
| unknown-attribute | 400 |
| bad-element | 400 |
| unknown-element | 400 |
| unknown-namespace | 400 |
| access-denied | 403 |
| lock-denied | 409 |
| resource-denied | 409 |
| rollback-failed | 500 |
| data-exists | 409 |
| data-missing | 409 |
| operation-not-supported | 501 |
| operation-failed | 500 |
| partial-operation | 500 |
| malformed-message | 400 |
+-------------------------+-------------+
Mapping from error-tag to status code
6.1. Error Response Message
When an error occurs for a request message on a data resource or an
operation resource, and a "4xx" class of status codes (except for
status code "403"), then the server SHOULD send a response body
containing the information described by the following YANG data
definition statement:
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container errors {
config false;
list error {
reference "RFC 6241, Section 4.3";
leaf error-type {
mandatory true;
type enumeration {
enum transport;
enum rpc;
enum protocol;
enum application;
}
}
leaf error-tag {
mandatory true;
type string;
}
leaf error-app-tag {
type string;
}
leaf error-path {
type string; // YANG-API encoded instance-identifier
}
leaf error-message {
type string;
}
container error-info {
// anyxml content here
}
}
}
Example:
The following example shows an error returned for an "lock-denied"
error on a datastore resource.
POST /yang-api/operations/lock-datastore HTTP/1.1
Host: example.com
The server might respond:
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HTTP/1.1 409 Conflict
Date: Mon, 23 Apr 2012 17:11:00 GMT
Server: example-server
Content-Type: application/vnd.yang.api+json
{
"errors": {
"error": {
"error-type": "protocol",
"error-tag": "lock-denied",
"error-message": "Lock failed, lock is already held",
}
}
}
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7. RelaxNG Grammar
TBD
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8. YANG-API module
RFC Ed.: update the date below with the date of RFC publication and
remove this note.
<CODE BEGINS> file "ietf-yang-api@2012-11-30.yang"
module ietf-yang-api {
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-api";
prefix "api";
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>";
description
"This module contains a collection of YANG language extensions
to describe REST API Resources using YANG data definition
statements.
Copyright (c) 2012 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
// RFC Ed.: replace XXXX with actual RFC number and remove this
// note.
// RFC Ed.: remove this note
// Note: extracted from draft-bierman-netconf-yang-api-01.txt
// RFC Ed.: update the date below with the date of RFC publication
// and remove this note.
revision 2012-11-30 {
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description
"Initial revision.";
reference
"RFC XXXX: YANG-API Protocol.";
}
/*
* Extensions
*/
extension optional-key {
description
"This extension is used to allow the client to create
a new instance of a resource without providing a
value for the key leaf containing this statement.
This extension is ignored for NETCONF, and only
applies to YANG-API resources and fields.
This extension is ignored unless it appears
directly within a 'leaf' data definition statement.";
}
}
<CODE ENDS>
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9. IANA Considerations
This document registers one URI in the IETF XML registry [RFC3688].
Following the format in RFC 3688, the following registration is
requested to be made.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-api
Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
This document registers one YANG module in the YANG Module Names
registry [RFC6020].
name: ietf-yang-api
namespace: urn:ietf:params:xml:ns:yang:ietf-yang-api
prefix: api
reference: RFC XXXX
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10. Security Considerations
TBD
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11. Change Log
-- RFC Ed.: remove this section before publication.
11.1. 00-01
o expanded introduction
o removed transactions
o removed capabilities
o simplified editing model
o removed global protocol operations from ietf-yang-api.yang
o changed RPC operation terminology to protocol operation
o updated JSON draft reference
o updated open issues section
o updated IANA section
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12. Open Issues
o Which WG should do this work? NETCONF? NETMOD? It is not clear
since YANG-API builds on concepts and standards from documents
owned by both working groups.
o Resource creation order and other dependencies between resources
are not well identified in YANG. YANG has leafrefs and instance-
identifiers, which can be used to identify some order
dependencies. Are any new mechanisms needed in YANG-API needed to
identify resource creation order and other dependency
requirements?
o There is no "message-id" field in a YANG-API message. Is a
message identifier needed? If so, should either the "Message-ID"
or "Content-ID" header from RFC 2392 be used for this purpose?
o Should sessions be used or not? Should "reusable sessions" be
used? Better for auditing? How does locking of the /yang-api/
datastore resource work for multiple edits if a session is 1
operation? When does the server release the lock and decide it
has been abandoned or client was disconnected?
o What syntax should be used for the "select" query parameter?
o Should the "/yang-api/modules" field within the API resource be a
separate resource, with its own timestamp? Currently the API
timestamp is coupled to any changes to the list of loaded modules.
Should the API resource be static and cacheable?
o What to do about no REMOVE operation, just DELETE? The effect is
local to the request; in a NETCONF edit-config it is worse, since
the netconf request might create/delete/modify many nodes
o Should every YANG data node be a data resource and every YANG RPC
statement an operation resource? Is a YANG extension needed to
allow data modeler control of resource boundaries?
o Encoding of leafrefs? Is there some additional meta-data needed?
Do leafref nodes need to be identified in responses (RFC 5988) or
is the YANG module definition sufficient to provide this meta-
data?
o What should the default algorithm be for defining data resources?
Should the default for an augment from another namespace be to
start a new resource? Top-level data node defaults as a resource
OK?
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o Is the token "entries" legal in the YANG-API usage of Range? What
units should be used? "bytes" is the only token defined by HTTP.
o Are all header lines used by YANG-API supported by common
application frameworks, such as FastCGI and WSGI? If not, then
should query parameters be used instead, since the QUERY_STRING is
widely available to WEB applications?
o Should the <errors> element returned in error responses be a
separate media type?
o How should additional datastores be supported, which may be added
to the NETCONF/NETMOD framework in the future?
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13. Example YANG Module
module example-jukebox {
namespace "http://example.com/ns/example-jukebox";
prefix "jbox";
import ietf-yang-api { prefix api; }
organization "Example, Inc.";
description "Example Jukebox Data Model Module";
revision "2012-05-30";
identity genre {
description "Base for all genre types";
}
// abbreviated list of genre classifications
identity Alternative {
base genre;
}
identity Blues {
base genre;
}
identity Country {
base genre;
}
identity Jazz {
base genre;
}
identity Pop {
base genre;
}
identity Rock {
base genre;
}
container jukebox {
presence
"An empty container indicates that the jukebox
service is available";
container library {
list artist {
key index;
unique name;
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leaf index {
api:optional-key;
type uint32;
description
"Optional key used instead of natural key for
example. Also rare but possible artists with
the same name are really different entities.";
}
leaf name {
type string;
}
list album {
key name;
leaf name {
type string {
length "1 .. max";
}
}
leaf genre {
type identityref { base genre; }
}
leaf year {
type uint16 {
range "1900 .. max";
}
}
list song {
api:optional-key;
key index;
ordered-by user;
leaf index {
type uint32;
}
leaf name {
mandatory true;
type string;
}
leaf location {
mandatory true;
type string;
}
leaf format {
type string;
}
leaf length {
units "seconds";
type uint32;
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}
}
}
}
leaf artist-count {
config false;
type uint32;
units "songs";
description "Number of artists in the library";
}
leaf album-count {
config false;
type uint32;
units "albums";
description "Number of albums in the library";
}
leaf song-count {
type uint32;
units "songs";
description "Number of songs in the library";
}
}
list playlist {
description
"Example configuration data resource";
key name;
leaf name {
type string;
}
leaf description {
type string;
}
list song {
description
"Example nested configuration data resource";
ordered-by user;
key index;
leaf index {
api:optional-key;
type uint32;
}
leaf id {
mandatory true;
type instance-identifier;
description
"Song identifier. Must identify an instance of
/jukebox/library/artist/album/song.
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The id is not the key to allow duplicates
in a playlist";
}
}
}
container player {
leaf gap {
description "Time gap between each song";
units "tenths of seconds";
type decimal64 {
fraction-digits 1;
range "0.0 .. 2.0";
}
}
}
}
rpc play {
description "Control function for the jukebox player";
input {
leaf playlist {
type string;
mandatory true;
description "playlist name";
}
leaf song-number {
type uint32;
mandatory true;
description "Song number in playlist to play";
}
}
}
}
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14. Normative References
[I-D.lhotka-netmod-json]
Lhotka, L., "Modeling JSON Text with YANG",
draft-lhotka-netmod-yang-json-00 (work in progress),
October 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, March 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
October 2010.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
March 2012.
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Authors' Addresses
Andy Bierman
YumaWorks
Email: andy@yumaworks.com
Martin Bjorklund
Tail-f Systems
Email: mbj@tail-f.com
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