| Network Working Group | R. Murray |
| Internet-Draft | B. Niven-Jenkins |
| Intended status: Standards Track | Velocix (Alcatel-Lucent) |
| Expires: January 3, 2015 | July 2, 2014 |
CDNI Control Interface / Triggers
draft-ietf-cdni-control-triggers-03
This document describes the part of the CDN Interconnect Control Interface that allows a CDN to trigger activity in an interconnected CDN that is configured to deliver content on its behalf. The upstream CDN can use this mechanism to request that the downstream CDN pre-positions metadata or content, or that it re-validate or purge metadata or content. The upstream CDN can monitor the status of activity that it has triggered in the downstream CDN.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 3, 2015.
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
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[RFC6707] introduces the Problem scope for CDN Interconnection (CDNI) and lists the four categories of interfaces that may be used to compose a CDNI solution (Control, Metadata, Request Routing, Logging).
[I-D.ietf-cdni-framework] expands on the information provided in [RFC6707] and describes each of the interfaces and the relationships between them in more detail.
This document describes the "CI/T" interface, "CDNI Control interface / Triggers". It does not consider those parts of the control interface that relate to configuration, bootstrapping or authentication of CDN Interconnect interfaces. Requirements for CI/T are the "High" and "Medium" priority requirements for the CI identified in section 4 of [I-D.ietf-cdni-requirements], reproduced here for convenience:
This document reuses the terminology defined in [RFC6707].
A trigger, sent from the uCDN to the dCDN, is a request for dCDN to do some work relating to data originating from the uCDN.
The trigger may request action on either metadata or content, the following actions can be requested:
The CI/T interface is a web service offered by the dCDN. It allows creation and deletion of triggers, and tracking of the triggered activity. When the dCDN accepts a trigger it creates a resource describing status of the triggered activity, a Trigger Status Resource. The uCDN MAY poll Trigger Status Resources to monitor progress.
Requests to invalidate and purge metadata or content apply to all variants of that data with a given URI.
The dCDN maintains a collection of Trigger Status Resources for each uCDN, each uCDN only has access to its own collection and the location of that collection is shared when CDN interconnection is established.
To trigger activity in the dCDN, the uCDN will POST to the collection of Trigger Status Resources. If the dCDN accepts the trigger, it creates a new Trigger Status Resource and returns its location to the uCDN. To monitor progress, the uCDN MAY GET the Trigger Status Resource. To cancel a trigger, or remove a trigger from the collection once its activity has been completed, the uCDN MAY DELETE the Trigger Status Resource.
In addition to the collection of all Trigger Status Resources for uCDN, uCDN has access to filtered views of that collection. These filtered views are defined in Section 3 and include collections of active and completed triggers. These collections provide a mechanism for polling the status of multiple jobs.
Figure 1 is an example showing the basic message flow used by the uCDN to trigger activity in dCDN, and for uCDN to discover the status of that activity. Only successful triggering is shown. Examples of the messages are given in Section 7.
uCDN dCDN
| (1) POST http://dcdn.example.com/triggers/uCDN |
[ ] --------------------------------------------------> [ ]--+
| [ ] | (2)
| (3) HTTP 201 Response [ ]<-+
[ ] <-------------------------------------------------- [ ]
| Loc: http://dcdn.example.com/triggers/uCDN/123 |
| |
. . .
. . .
. . .
| |
| (4) GET http://dcdn.example.com/triggers/uCDN/123 |
[ ] --------------------------------------------------> [ ]
| [ ]
| (5) HTTP 200 Trigger Status Resource [ ]
[ ] <-------------------------------------------------- [ ]
| |
| |
Figure 1: Basic CDNI Message Flow for Triggers
The steps in Figure 1 are:
The remainder of this document describes the messages, Trigger Status Resources, and collections of Trigger Status Resources in more detail.
Timing of triggered activity is under the dCDN's control, including its start-time and pacing of the activity in the network.
Invalidate and purge triggers MUST be applied to all data acquired before the trigger was created in the dCDN. The dCDN may apply the triggers to data acquired after trigger creation.
If the uCDN wishes to invalidate or purge content, then immediately pre-position replacement content at the same URLs, it SHOULD ensure the dCDN has completed the invalidate/purge before initiating the prepositioning. Otherwise, the dCDN may pre-position the new content then immediately invalidate or purge it (as a result of the two uCDN requests running in parallel).
Each Trigger Request may operate on multiple data items. The trigger MUST NOT be reported as "complete" unless all actions can be completed successfully, otherwise it MUST be reported as "failed" or "processed". The reasons for failure and URLs or Patterns affected SHOULD be enumerated in the Trigger Status Resource. For more detail, see section Section 4.5.
If a dCDN is also acting as a uCDN in a cascade, it MUST forward triggers to any downstream CDNs that may have data affected by the trigger. The trigger MUST NOT be reported as complete in a CDN until it is complete in all of its downstream CDNs. A trigger MAY be reported as failed as soon as it fails in a CDN or in any of its downstream CDNs.
As described in Section 2, Trigger Status Resources exist in dCDN to report the status of activity triggered by each uCDN.
A collection of Trigger Status Resources is a resource that contains a reference to each Trigger Status Resource in that collection.
To trigger activity in the dCDN, the uCDN creates a new Trigger Status Resource by posting to the dCDN's collection of uCDN's Trigger Status Resources. The URL of each Trigger Status Resource is generated by the dCDN when it accepts the trigger, and returned to the uCDN. This immediately enables the uCDN to check the status of that trigger.
The dCDN MUST present a different set of Trigger Status Resources to each interconnected uCDN. Trigger Status Resources belonging to a uCDN MUST NOT be visible to any other client. The dCDN may, for example, achieve this by offering different collection URLs to uCDNs, or by filtering the response based on the client uCDN.
The dCDN resource representing the collection of all the uCDN's Trigger Status Resources is accessible to the uCDN. This collection lists all of the uCDN triggers that have been accepted by the dCDN, and have not yet been deleted by the uCDN, or expired and removed by the dCDN (as described in section Section 4.3).
In order to allow the uCDN to check status of multiple jobs in a single request, the dCDN SHOULD also maintain collections representing filtered views of the collection of all Trigger Status Resources. The filtered collections are:
This section describes an interface to enable an upstream CDN to trigger defined activities in a downstream CDN. The interface is intended to be independent of the set of activities defined now, or that may be defined in future.
CI/T is built on the principles of RESTful web services. Requests are made over HTTP, and the HTTP Method defines the operation the request would like to perform. The corresponding HTTP Response returns the status of the operation in the HTTP Status Code and returns the current representation of the resource (if appropriate) in the Response Body. HTTP Responses from servers implementing CI/T that contain a response body SHOULD include an ETag to enable validation of cached versions of returned resources.
Servers implementing CI/T MUST support the HTTP GET, HEAD, POST and DELETE methods as defined in [RFC7231]. The only representation specified in this document is JSON, [RFC7159].
The URL of the dCDN's collections of Trigger Status Resources need to be either discovered by, or configured in, the uCDN. The mechanism for discovery of those URLs is outside the scope of this document.
Trigger Requests are POSTed to the dCDN's collection of all Trigger Status Resources. If the trigger is accepted by the dCDN, it creates a new Trigger Status Resource and returns its URI to the dCDN in an HTTP 201 response. The triggered activity can then be monitored by the uCDN using that resource and the collections described in Section 3.
The URI of each Trigger Status Resource is returned to the uCDN when it is created. This means all Trigger Status Resources can be discovered, so CI/T servers are free to assign whatever structure they desire to the URIs for CI/T resources. CI/T clients MUST NOT make any assumptions regarding the structure of CI/T URIs or the mapping between CI/T objects and their associated URIs. Therefore any URIs present in the examples below are purely illustrative and are not intended to impose a definitive structure on CI/T interface implementations.
The CI/T interface builds on top of HTTP, so CI/T servers may make use of any HTTP feature when implementing the CI/T interface. For example, a CI/T server may make use of HTTP's caching mechanisms to indicate that a requested response/representation has not been modified, reducing the processing needed to determine whether the status of triggered activity has changed.
This specification is neutral with regard to the transport below the HTTP layer.
The dCDN MUST ensure that activity triggered by the uCDN only affects metadata or content originating from that uCDN. Since only one CDN can be authoritative for a given item of metadata or content, this requirement means there cannot be any "loops" in trigger requests between CDNs.
To create a new trigger, the uCDN makes an HTTP POST to the unfiltered collection of its triggers. The request body of that POST is a Trigger Request.
The dCDN validates and authenticates that request, if it is malformed or the uCDN does not have sufficient access rights it MAY reject the request immediately. In this case, it MUST respond with an appropriate 4xx HTTP error code and a resource MUST NOT be created on dCDN.
If the request is accepted, the uCDN MUST create a new Trigger Status Resource. The HTTP response to the dCDN MUST have status code 201 and the URI of the Trigger Status Resource in the Location header field. The HTTP response SHOULD include the content of the newly created Trigger Status Resource, this is recommended particularly in cases where the trigger has completed immediately.
Once a Trigger Status Resource has been created the dCDN MUST NOT re-use its location, even after that resource has been removed.
The "request" property of the Trigger Status Resource contains the information posted in the body of the Trigger Request. Note that this need not be a byte-for-byte copy. For example, in the JSON representation the dCDN may re-serialise the information differently.
If the dCDN is not able to track triggered activity, it MUST indicate that indicate that it has accepted the request but will not be providing further status updates. To do this, it sets the "status" of the Trigger Status Resource to "processed". In this case, CI/T processing should continue as for a "complete" request, so the Trigger Status Resource MUST be added to the dCDN's collection of Complete Triggers. The dCDN SHOULD also provide an estimated completion time for the request, by using the "etime" property of the Trigger Status Resource. This will allow the uCDN to schedule prepositioning after an earlier delete of the same URLs is expected to have finished.
If the dCDN is able to track triggered activity, the trigger is queued by the dCDN for later action, the "status" property of the Trigger Status Resource MUST be "pending". Once trigger processing has started the "status" MUST be "active". Finally, once the triggered activity is complete, the trigger status MUST be set to "complete" or "failed".
A trigger may result in no activity in the dCDN if, for example, it is an invalidate or purge request for data the dCDN has not yet acquired, or a prepopulate request for data it has already acquired and which is still valid. In this case, the "status" of the Trigger Status Resource MUST be "processed" or "complete", and the Trigger Status Resource MUST be added to the dCDN's collection of Complete Triggers.
Once created, Trigger Status Resources may be deleted by the uCDN but not modified. The dCDN MUST reject PUT and POST requests from the uCDN to Trigger Status Resources using HTTP status code 403.
The uCDN has two ways to check progress of activity it has triggered in the dCDN, described in the following sections.
To check for change in status of a resource or collection of resources without re-fetching the whole resource or collection, Entity Tags SHOULD be used by the uCDN as cache validators, as defined in [RFC7232].
The dCDN SHOULD use the cache control headers for responses to GETs for Trigger Status Resources and Collections to indicate the frequency at which it recommends uCDN should poll for change.
The uCDN can fetch the collection of its Trigger Status Resources, or filtered views of that collection.
This makes it possible to poll status of all triggered activity in a single request. If the dCDN moves a Trigger Status Resource from the Active to the Completed collection, the uCDN may chose to fetch the result of that activity.
When polling in this way, the uCDN SHOULD use HTTP Entity Tags to monitor for change, rather than repeatedly fetching the whole collection.
The uCDN has a reference (URI provided by the dCDN) for each Trigger Status Resource it has created, it may fetch that resource at any time.
This MAY be used to retrieve progress information, and to fetch the result of triggered activity.
The uCDN MAY delete Trigger Status Resources at any time, using the HTTP DELETE method.
Once deleted, the references to a Trigger Status Resource MUST be removed from all Trigger Status Resource collections. Subsequent requests for the resource MUST be handled as required by HTTP, and so will receive responses with status 404 or 410.
If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD NOT start processing of that activity. Deleting a "pending" trigger does not however guarantee that it is not started because the uCDN cannot control the timing of that activity. Processing may, for example, start after the DELETE is sent by the uCDN but before the DELETE is processed by the dCDN.
If an "active" Trigger Status Resource is deleted, the dCDN MAY stop processing the triggered activity. However, as with deletion of a "pending" trigger, the dCDN does not guarantee this.
Deletion of a "complete", "processed" or "failed" Trigger Status Resource requires no processing in the dCDN other than deletion of the resource.
The dCDN MAY choose to automatically delete Trigger Status Resources some time after they become "complete", "processed" or "failed". In this case, the dCDN will remove the resource and respond to subsequent requests for it with HTTP status 404 or 410.
If the dCDN performs this housekeeping, it MUST have reported the length of time after which completed Trigger Status Resources become stale via a property of the collection of all Trigger Status Resources. It is recommended that Trigger Status Resources are not automatically deleted for at least 24 hours after they become "complete", "processed" or "failed".
To ensure it has access to the status of its completed and failed triggers, it is recommended that the uCDN's polling interval is half the time after which records for completed activity will be considered stale.
A CI/T server may reject a trigger request using HTTP status codes. For example, 400 if the request is malformed, or 401 if the client does not have permission to create triggers or it is trying to act on another CDN's data.
If any part of the trigger request fails, the trigger SHOULD be reported as "failed" once its activity is complete or if no further errors will be reported. The "errors" property in the Trigger Status Resource will be used to enumerate which actions failed and the reasons for failure, and may be present while the trigger is still "pending" or "active", if the trigger is still running for some URLs or Patterns in the trigger request.
Once a request has been accepted, processing errors are reported in the Trigger Status Resource using a list of "ErrorDesc". Each ErrorDesc is used to report errors against one or more of the URLs or Patterns in the trigger request.
If a surrogate affected by a trigger is offline in the dCDN, or the dCDN is unable to pass a trigger request on to any of its cascaded dCDNs; the dCDN SHOULD report an error if the request is abandoned. Otherwise, it SHOULD keep the trigger in state "pending" or "active" until it's acted upon or the uCDN chooses to cancel it. Or, if the request is queued and the dCDN will not report further status, the dCDN MAY report the trigger as "processed", in which case it SHOULD also provide an estimated completion time.
Note that an "invalidate" trigger may be reported as "complete" when surrogates that may have the data are offline. In this case, surrogates MUST NOT use the affected data without first revalidating it when they are back online. This does not apply to "preposition" or "purge" triggers.
Properties of Trigger Requests are defined in the following subsections.
To refer to content in the dCDN, the uCDN MUST present URLs in the same form clients will use to access content in that dCDN, after transformation to remove any surrogate-specific parts of a 302-redirect URL form. By definition, it is always possible to locate content based on URLs in this form.
If content URLs are transformed by an intermediate CDN in a cascade, that intermediate CDN MUST transform URLs in trigger requests it passes to its dCDN.
When processing trigger requests, CDNs MUST ignore the URL scheme (http or https) in comparing URLs. For example, for an invalidate or purge trigger, content MUST invalidated or purged regardless of the protocol clients use to request it.
An ErrorDesc object is used to report failure for URLs and patterns in a trigger request.
This section describes the simpler data types that are used for properties of Trigger Status resources.
This type defines the type of action being triggered, permitted actions are:
This type describes the current status of a Trigger, possible values are:
This type describes a set of references to metadata or content, it is simply a list of absolute URLs.
Times are expressed in seconds since the UNIX epoch.
This type is used by dCDN to report failures in trigger processing.
The encoding for a CI/T object is a JSON object containing a dictionary of (key,value) pairs where the keys are the property names, and the values are the associated property values.
The keys of the dictionary are the names of the properties associated with the object and are therefore dependent on the specific object being encoded (i.e. dependent on the MIME Media Type of the returned resource). Likewise, the values associated with each key are dependent on the specific object being encoded (i.e. dependent on the MIME Media Type of the returned resource).
The "trigger" property of the top level JSON object lists the requested action.
Object keys in JSON are case sensitive and therefore any dictionary key defined by this document (for example the names of CI/T object properties) MUST always be represented in lowercase.
In addition to the properties of an object, the following additional keys MAY be present.
A PatternMatch is encoded as a JSON Object containing a string to match and flags describing the type of match.
Key: case-sensitive
Key: match-query-string
Example of case-sensitive prefix match against "http://www.example.com/trailers/":
{
"pattern": "http://www.example.com/trailers/*",
"case-sensitive": true
}
ErrorDesc is encoded as a JSON object with the following keys:
Keys: metadata.urls, content.urls
Keys: metadata.patterns, content.patterns
One of the strings "EMETA", "ECONTENT", "EPERM", "EREJECT" or "ECDN".
Table 1 lists the MIME Media Type for the trigger request, and each trigger object (resource) that is retrievable through the CI/T interface.
| Data Object | MIME Media Type |
|---|---|
| TriggerRequest | application/cdni.ci.TriggerRequest+json |
| TriggerStatus | application/cdni.ci.TriggerStatus+json |
| TriggerCollection | application/cdni.ci.TriggerCollection+json |
The following sections provide examples of different CI/T objects encoded as JSON.
No authentication is shown in the following illustrative examples, it is anticipated that authentication mechanisms will be aligned with other CDNI Interfaces as and when those mechanisms are defined.
Discovery of the triggers interface is out of scope of this document. In an implementation, all URLs are under the control of the dCDN. The uCDN MUST NOT attempt to ascribe any meaning to individual elements of the path. In examples in this section, the following URLs are used as the location of the collections of triggers:
Examples of uCDN triggering activity in dCDN:
An example of a preposition request, a POST to the "AllTriggers" collection.
Note that "metadata.patterns" and "content.patterns" are not allowed in a preposition trigger request.
REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni.ci.TriggerRequest+json
Content-Length: 315
{
"trigger" : {
"type": "preposition",
"metadata.urls" : [ "http://metadata.example.com/a/b/c" ],
"content.urls" : [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
]
}
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 02 Jul 2014 18:57:19 GMT
Content-Length: 472
Content-Type: application/cdni.ci.TriggerStatus+json
Location: http://dcdn.example.com/triggers/0
Server: example-server/0.1
{
"ctime": 1404327439,
"etime": 1404327447,
"mtime": 1404327439,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
An example of an invalidate request, another POST to the "AllTriggers" collection. This instructs the dCDN to re-validate the content at "http://www.example.com/a/index.html", as well as any metadata and content whose URLs are prefixed by "http://metadata.example.com/a/b/" and "http://www.example.com/a/b/" respectively, using case-insensitive matching.
REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni.ci.TriggerRequest+json
Content-Length: 352
{
"trigger" : {
"type": "invalidate",
"metadata.patterns" : [
{ "pattern" : "http://metadata.example.com/a/b/*" }
],
"content.urls" : [ "http://www.example.com/a/index.html" ],
"content.patterns" : [
{ "pattern" : "http://www.example.com/a/b/*",
"case-sensitive" : true
}
]
}
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Length: 551
Content-Type: application/cdni.ci.TriggerStatus+json
Location: http://dcdn.example.com/triggers/1
Server: example-server/0.1
{
"ctime": 1404327440,
"etime": 1404327448,
"mtime": 1404327440,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "http://www.example.com/a/b/*"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "http://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
Once triggers have been created, the uCDN can check their status as shown in these examples.
The uCDN can fetch the set of all the triggers it has created and which have not yet been deleted or removed as expired. After creation of the "preposition" and "invalidate" triggers shown above, this collection might look as follows:
REQUEST:
GET /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Wed, 02 Jul 2014 18:58:20 GMT
Server: example-server/0.1
Etag: "9179988753593038498"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
The filtered collections are also available to uCDN. Before the dCDN starts processing the two triggers shown above, both will appear in the collection of Pending Triggers, for example:
RREQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Wed, 02 Jul 2014 18:58:20 GMT
Server: example-server/0.1
Etag: "5012053611544832286"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
At this point, if no other triggers had been created, the other filtered views of the triggers would be empty. For example:
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 56
Expires: Wed, 02 Jul 2014 18:58:20 GMT
Server: example-server/0.1
Etag: "2986340333785000363"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": []
}
The Trigger Status Resources can also be examined for detail about individual triggers. For example, for the "preposition" and "invalidate" triggers from previous examples:
REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 472
Expires: Wed, 02 Jul 2014 18:58:20 GMT
Server: example-server/0.1
Etag: "-3651695664007658154"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Type: application/cdni.ci.TriggerStatus+json
{
"ctime": 1404327439,
"etime": 1404327447,
"mtime": 1404327439,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
REQUEST:
GET /triggers/1 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 551
Expires: Wed, 02 Jul 2014 18:58:20 GMT
Server: example-server/0.1
Etag: "-7664987687828084413"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:20 GMT
Content-Type: application/cdni.ci.TriggerStatus+json
{
"ctime": 1404327440,
"etime": 1404327448,
"mtime": 1404327440,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "http://www.example.com/a/b/*"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "http://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
The uCDN may use the Entity Tags of collections or resources when polling for change in status, as shown in the following examples:
REQUEST: GET /triggers/pending HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* If-None-Match: "5012053611544832286" RESPONSE: HTTP/1.1 304 Not Modified Content-Length: 0 Expires: Wed, 02 Jul 2014 18:58:20 GMT Server: example-server/0.1 Etag: "5012053611544832286" Cache-Control: max-age=60 Date: Wed, 02 Jul 2014 18:57:20 GMT Content-Type: application/cdni.ci.TriggerCollection+json
REQUEST: GET /triggers/0 HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* If-None-Match: "-3651695664007658154" RESPONSE: HTTP/1.1 304 Not Modified Content-Length: 0 Expires: Wed, 02 Jul 2014 18:58:20 GMT Server: example-server/0.1 Etag: "-3651695664007658154" Cache-Control: max-age=60 Date: Wed, 02 Jul 2014 18:57:20 GMT Content-Type: application/cdni.ci.TriggerStatus+json
When the triggered activity is complete, the contents of the filtered collections will be updated, along with their Entity Tags. For example, when the two example triggers are complete, the collections of pending and complete triggers may look like:
REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 56
Expires: Wed, 02 Jul 2014 18:58:24 GMT
Server: example-server/0.1
Etag: "-4471185573414616962"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:24 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": []
}
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Wed, 02 Jul 2014 18:58:31 GMT
Server: example-server/0.1
Etag: "-1508172875796647067"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:31 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
To request the dCDN to cancel a Trigger, the uCDN may delete the Trigger Resource. It may also delete completed and failed triggers to reduce the size of the collections. For example, to remove the "preposition" request from earlier examples:
REQUEST: DELETE /triggers/0 HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* RESPONSE: HTTP/1.1 204 No Content Date: Wed, 02 Jul 2014 18:57:31 GMT Content-Length: 0 Content-Type: text/html; charset=UTF-8 Server: example-server/0.1
This would, for example, cause the collection of completed triggers shown in the example above to be updated to:
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 106
Expires: Wed, 02 Jul 2014 18:58:31 GMT
Server: example-server/0.1
Etag: "-1842390246836476263"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 18:57:31 GMT
Content-Type: application/cdni.ci.TriggerCollection+json
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/1"
]
}
In this example the uCDN has requested prepositioning of "http://newsite.example.com/index.html", but the dCDN was unable to locate metadata for that site:
REQUEST:
GET /triggers/2 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 505
Expires: Wed, 02 Jul 2014 19:16:48 GMT
Server: example-server/0.1
Etag: "-6310233270471598826"
Cache-Control: max-age=60
Date: Wed, 02 Jul 2014 19:15:48 GMT
Content-Type: application/cdni.ci.TriggerStatus+json
{
"ctime": 1404328544,
"errors": [
{
"content.urls": [
"http://newsite.example.com/index.html"
],
"description":
"No HostIndex entry found for newsite.example.com",
"error": "EMETA"
}
],
"etime": 1404328552,
"mtime": 1404328548,
"status": "active",
"trigger": {
"content.urls": [
"http://newsite.example.com/index.html"
],
"type": "preposition"
}
}
The IANA is requested to allocate the following MIME Media Types in the MIME Media Types registry:
Section 6.2 of the present document.
Use of these types is specified in
A CI/T dCDN server implementation MUST support TLS transport for HTTP (https) as per [RFC2818]. The use of TLS for transport of the CI/T interface allows the dCDN and the uCDN to authenticate each other (to ensure they are receiving trigger requests from, or reporting status to, an authenticated CDN).
HTTP requests that attempt to access or operate on CI/T data belonging to another CDN MUST be rejected using either HTTP "403 Forbidden" or "404 Not Found". (Note that in a "diamond" configuration, where one uCDN's content can be acquired via more than one directly-connected uCDN, it may not be possible for the dCDN to determine from which uCDN it acquired content. In this case, it MUST allow each upstream that may have been responsible for acquisition of that content to act upon it using trigger requests.)
Trigger creation requests that attempt to operate on metadata or content not acquired from the uCDN making the request MUST be rejected. The rejection can either be signalled to dCDN using HTTP "403 Forbidden" or "404 Not Found", or a Trigger Status Resource can be created with an ErrorDesc value of EPERM for any affected URLs.
In an environment where any such protection is required, TLS SHOULD be used for transport of the CI/T requests and responses, unless alternate methods are used for ensuring that only authorised clients are able to access their own data (such as setting up an IPsec tunnel between the two CDNs, or using a physically secured internal network between two CDNs that are owned by the same corporate entity). Both parties of the transaction (the uCDN and the dCDN) SHOULD use mutual authentication.
A CI/T implementation MUST support the TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite ([RFC5288]). An implementation of the CI/T Interface SHOULD prefer cipher suites which support perfect forward secrecy over cipher suites that don't.
This document does not define a specific mechanism to protect against Denial of Service (DoS) attacks on the CI/T. However, CI/T endpoints can be protected against DoS attacks through the use of TLS transport and/or via mechanisms outside the scope of the CI/T interface, such as firewalling or use of Virtual Private Networks (VPNs).
The authors thank Kevin Ma for his ongoing input.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC3986] | Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. |
| [RFC7159] | Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, March 2014. |
| [RFC7231] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, June 2014. |
| [RFC7232] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests", RFC 7232, June 2014. |