| Internet Engineering Task Force | H. Bellur |
| Internet-Draft | C. Wendt, Ed. |
| Intended status: Standards Track | Comcast |
| Expires: April 21, 2016 | October 19, 2015 |
Distributed Registry Protocol
draft-wendt-modern-drip-00
This document describes a protocol for allowing a distributed set of nodes to synchronize a set of information in real-time with minimal amount of delay. This is useful for registry types of information like identity and telephone numbers with associated routing and ownership information and could be extended to support other distributed real-time information updates as well.
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 April 21, 2016.
Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
This document describes the Distributed Registry Protocol (DRiP). DRiP defines a set of peer protocols for how an arbitrary number of nodes arranged in a distributed mesh architecture can be used to synchronize data in real-time across a network.
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].
DRiP uses a mix of a gossip protocol with update counters for distribution of key-value data with the addition of a voting system to avoid race conditions on writing of key-value data.
The DRiP architecture is based on a peer-to-peer communication model where a given node associated with a data store is not necessarily aware of the total number of nodes in the entire network. Minimally, every node should reachable by at least one multi-node path from every other node. Each node in the DRiP network maintains a list of peer nodes from which it receives and transmits updates. Information is propagated by forwarding to it's peer nodes until the information received by a node has already been received.
___ ___ ___ ___
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
| Data | | Data |
| Store | | Store |
_|_ Cluster _|_ _|_ Cluster _|_
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
\ /
\ /
_\___ DRIP _ /__
|Node |------------|Node |
| A | HTTPS | C |
|_____| |_____|
\H H/
D\T T/D
R\T P/R
I\P P/I
P\S S/P
__\__ / DRIP _____
|Node |------------|Node |
| B | HTTPS | D |
|_____| |_____|
/ /
___ ___ / __/_ ___
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
| Data | | Data |
| Store | | Store |
_|_ Cluster _|_ _|_ Cluster _|_
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
Distributed Mesh Architecture
All nodes in the distributed mesh MUST agree upon a specific key-value data model. The choice of data store is implementation specific.
All nodes MUST be configured with at least one peer node before propagation.
A node MUST ignore any updates or commands it receives from other nodes that are not configured as peer nodes.
All nodes MUST send a periodic heartbeat or keep-alive message via HTTPS to the respective peer nodes. If a heartbeat is not received the peer node is removed from the list of active peer nodes.
The peer node should maintain a state that defines whether it is active, inactive, or synchronizing key-value data with a peer node.
The node should proactively tell it's peer nodes its state by sending the following POST messages. The GET query is available for nodes to query the state of peer nodes.
Request:
POST /node/:nodeid/active
Description:
TBD
Example:
TBD
Request:
GET /state
Description:
A node should query the state of its peer node before it initiates a sync operation. This request responds with either "active" or "sync" or no response, if in "inactive" state.
Example:
TBD
Request:
POST /node/:nodeid/active
Description:
TBD
Example:
TBD
Custom HTTP header fields will be used to carry node specific information.
| Field Name | Description |
|---|---|
| DRiP-Node-ID | Each node in the mesh MUST have a unique identifier. An Initiator node MUST set its own node ID as the field value. A Receiver Node MUST NOT change the DRiP-Node-ID field value as it forward the HTTPS request to its peer nodes. |
| Field Name | Description |
|---|---|
| DRiP-Node-Counter | Every node maintains a count of the number of times it initiates key-value data propagation. This counter MUST be an unsigned type, typically, a 64 bit integer. The Initiator node MUST set this count as the field value. A Receiver Node MUST NOT change the DRiP-Node-Counter field value as it forward the HTTPS request to its peer nodes. |
| Field Name | Description |
|---|---|
| DRiP-Node-Counter-reset | A node can reset the count (to zero) of the number of times it initiates key-value data propagation. If the counter value is reset, prior to initiating data propagation, then this field value MUST be set to true. Otherwise, it MUST be set to false, at all times. A typical use case to reset the counter value is when the counter (of unsigned type) value wraps around. The Initiator node MUST set this field value to either true or false. A Receiver Node MUST NOT change the DRiP-Node-Counter-reset field value as it forward the HTTPS request to its peer nodes. |
| Field Name | Description |
|---|---|
| DRiP-Transaction-Type | The Initiator node MUST set this field value to be either "update" or "sync". A Receiver Node MUST NOT change the DRiP-Transaction-Type field value as it forward the HTTPS request to its peer nodes. |
| Field Name | Description |
|---|---|
| DRiP-Sync-Complete | For sync transaction type, the Initiator node MUST set this field value to be true, if synchronization is complete. Otherwise, this field value MUST be set to false. |
A node propagates key-value data to all its peer nodes except the the node from which it received data. For example, in Figure 1, when node B receives key-value data from node A, it will propagate the data received to nodes C and D but not back to node A.
For each transaction type (Update or Sync), the following set of actions MUST take place when a node receives a HTTPS request with propagated key-value data:
When an Initiator node has new data it wants to propagate to the distributed mesh, it initiates an Update. The Update consists of a two-phase commit (2PC) procedure in order to guarantee there are no race conditions for updating the same key's data, as well as for any error conditions in the distributed mesh that would cause the update to not complete for all nodes in the network.
The two phases are called the "voting" phase and the "commit" phase.
_________
----------------------->| |
| | Waiting |
| | For |
| ---------------------| Events |
| | (Update, |_________|
| | Start Timer)
| | --------------------------------
| | | Received Update From Peer Node |
| | | |
| | ______________|_ If key matches an |
| | | | in-progress update |
| ----------->| | vote "no". |
| | Waiting For | Otherwise, vote "yes". |
| | Response From | |
| | Peer Nodes |<-----------------------------
| | |
| ----| |----
| Timer | |________________| |
| Expired | | Received Votes
| | | From All Peer
| | | Nodes
| | _______________ |
| | | | |
| | | | |
| --->| |<---
| | Validating |
| (If all Votes | Votes |
| are "YES", | |
| propagate | |
| commit) | |
---------------|________________|
Update State Diagram
The voting phase is the phase where all nodes are queried to "vote" whether they are aware of any potential conflict that would cause the transaction not to complete.
The Initiator node MUST set a timeout period to get response from its peer nodes.
The peer nodes known to the initiator node will continue propagate the information to their peer nodes and so on. However, these peer nodes beyond the initiator node will no longer need to keep track of the time interval for responses. A node will stop continuing to propagate information when it determines it has received the same information again. This can be determined by keeping track of the counter and originating node id.
If all peer nodes vote "yes", then the second phase or commit phase in the local node is initiated. If any node in the distributed mesh votes "no" or if the timeout period expires and all peer nodes have not responded, then the commit of the information MUST NOT be completed. No action is taken for responses received after the timeout period.
Note: The voting procedure is intentionally split into two separate full HTTP transactions for reliability.
___ ___ ___ ___ ___ ___
|DB |_________|DB | |DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___| |___| |___|
| Data | | Data | | Data |
| Store | | Store | | Store |
_|_ Cluster _|_ _|_ Cluster _|_ _|_ Cluster _|_
|DB |_________|DB | |DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___| |___| |___|
\ \ |
\ \ |
_\___ Vote(HTTPS) _\___ Vote(HTTPS) |____
|Node | <---------- |Node | ----------> |Node |
| B |---------------| A |---------------| C |
|_____| ----------> |_____| <---------- |_____|
Yes/No Yes/No
Voting Phase
Request:
POST /voting
Description:
A post from either Initiator node or subsequent peer nodes to request a vote of "yes" or "no" whether the key-value data could be committed without error or conflict.
Example (using cURL)
Request
$ curl -i -H "Content-Type: application/json" -H "DRiP-Node-ID:
nodeA" -H "DRiP-Node-Counter: 1234" -H
"DRiP-Node-Counter-reset: false" -X POST -d '{<key-value
data>}' https://nodebregistry.com/voting
Response
HTTP/1.1 200 OK
Request:
POST /voting/peernode/:nodeid/response/:response
Description:
A POST from peer node back to node with response of vote.
Example (using cURL)
Request
$ curl -i -X POST http://nodearegistry.com/node/nodeA/response/yes
Response
HTTP/1.1 200 OK
The Initiator node, that originated the gossip, upon receiving a successful aggregated "yes" vote from all the peer nodes should start the commit phase. This node MUST commit the data to its data store. Subsequently, this information is propagated to all the nodes so that each node in the mesh will commit the same information in their respective data stores.
___ ___ ___ ___
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
| Data | | Data |
| Store | | Store |
_|_ Cluster _|_ _|_ Cluster _|_
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
\ /
\COMMIT /COMMIT
_\___ COMMIT _ /__
|Node |------------|Node |
| A | HTTPS | C |
|_____| |_____|
\H H/
\T T/
COMMIT\T P/COMMIT
\P P/
\S S/
__\__ / COMMIT _____
|Node |------------|Node |
| B | HTTPS | D |
|_____| |_____|
/ /
/COMMIT /COMMIT
___ ___/ _/__ ___
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
| Data | | Data |
| Store | | Store |
_|_ Cluster _|_ _|_ Cluster _|_
|DB |_________|DB | |DB |_________|DB |
|___| |___| |___| |___|
Commit Phase
Request:
POST /commit
Description:
A commit message is sent from Initiator or subsequent peer nodes to signal the Receiver node to commit the data to its data store.
Example (using cURL)
Request
$ curl -i -H "Content-Type: application/json" -H "DRiP-Node-ID:
nodeA" -H "DRiP-Node-Counter: 1234" -H
"DRiP-Node-Counter-reset: false" -X POST -d
'<key-value data>' https://nodebregistry.com/commit
Response
HTTP/1.1 200 OK
A node, either newly added to the distributed mesh or put back into service after being inactive, will get the state of a peer node to determine if it is in "active" state. If so, the node can immediately initiate a Sync transaction. The peer node MUST start propagating a comprehensive and complete set of key-value data from its data store.
The two phase commit does NOT apply here as the contents of the initiating node's data store is either outdated or empty. During this phase (HTTPS requests received will have DRiP-Sync-Complete field value set to false), this node SHOULD NOT become an Initiator node to provision data. While this transaction is going on, this node MUST vote "yes" to all real-time updates. The commits corresponding to the Updates should also be completed and reflected in the data store.
Request:
PUT /sync/node/:nodeid
Description:
API call for initiating a full registry synchronization from node to peer-node.
Example (using cURL)
Request
$ TBD
Response
HTTP/1.1 200 OK
TBD - definition of heartbeat
TBD - determination of the need to sync after heartbeat fails
When a node owner would like to create or modify particular key-value data, generally in the context of a registry, there MAY be a verification procedure that key-value data write or modification can be performed. This could include validating whether key-value data is entitled to be written, modified or subsequently propagated based on application policy. For example, identity or telephone number ownership or porting. The exact mechanics of this are out of scope of this document and are generally application specific.
All nodes MUST perform HTTP transactions using TLS as defined in [RFC7230].
Secure authentication of node to node communication is beyond the scope of this document, however best practices in terms of protecting the node API interface should be followed.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC7230] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014. |