ksnavely commented on a change in pull request #581: URL: https://github.com/apache/couchdb-documentation/pull/581#discussion_r470130225
########## File path: rfcs/016-fdb-replicator.md ########## @@ -0,0 +1,359 @@ +--- +name: Formal RFC +about: Submit a formal Request For Comments for consideration by the team. +title: 'Replicator Implementation On FDB' +labels: rfc, discussion +assignees: 'vatam...@apache.org' + +--- + +# Introduction + +This document describes the design of the replicator application for CouchDB +4.x. The replicator will rely on `couch_jobs` for centralized scheduling and +monitoring of replication jobs. + +## Abstract + +CouchDB replicator is the CouchDB application which runs replication jobs. +Replication jobs can be created from documents in `_replicator` databases, or +by `POST`-ing requests to the HTTP `/_replicate` endpoint. Previously, in +CouchDB <= 3.x replication jobs were mapped to individual cluster nodes and a +scheduler component would run up to `max_jobs` number of jobs at a time on each +node. The new design proposes using `couch_jobs`, as described in +[RFC](https://github.com/apache/couchdb-documentation/blob/master/rfcs/007-background-jobs.md), +to have a central, FDB-based queue of replication jobs. `couch_jobs` +application would manage job scheduling and coordination. The new design also +proposes using heterogeneous node types as defined in +[RFC](https://github.com/apache/couchdb-documentation/blob/master/rfcs/013-node-types.md) +such that replication jobs will be created only on `api_frontend` nodes and run +only on `replication` nodes. + +## Requirements Language + +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](https://www.rfc-editor.org/rfc/rfc2119.txt). + +## Terminology + +`_replicator` databases : A database that is either named `_replicator` or ends +with the `/_replicator` suffix. + +`transient` replications : Replication jobs created by `POST`-ing to the +`/_replicate` endpoint. + +`persistent` replications : Replication jobs created from a document in a +`_replicator` database. + +`continuous` replications : Jobs created with the `"continuous": true` +parameter. When this job reaches the end of the changes feed it will continue +waiting for new changes in a loop until the user removes the job. + +`normal` replications : Replication jobs which are not `continuous`. If the +`"continuous":true` parameter is not specified, by default, replication jobs +will be `normal`. + +`api_frontend node` : Database node which has the `api_frontend` type set to +`true` as described in +[RFC](https://github.com/apache/couchdb-documentation/blob/master/rfcs/013-node-types.md). +Replication jobs can be only be created on these nodes. + +`replication node` : Database node which has the `replication` type set to +`true` as described in +[RFC](https://github.com/apache/couchdb-documentation/blob/master/rfcs/013-node-types.md). +Replication jobs can only be run on these nodes. Review comment: It might be worth clarifying that no other activities take place other than replication on a `replication` node. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
