15.1. 2.0.x Branch

15.1.1. Version 2.0.0

  • Native clustering is now supported. Rather than use CouchDB replication between multiple, distinct CouchDB servers, configure a cluster of CouchDB nodes. These nodes will use an optimized Erlang-driven ‘internal replication’ to ensure data durability and accessibility. Combine a clustered CouchDB with a load balancer (such as haproxy) to scale CouchDB out horizontally. More details of the clustering feature are available in the Cluster Reference.
  • Futon replaced by brand-new, completely re-engineered Fauxton interface. URL remains the same.
  • The new Mango Query Server provides a simple JSON-based way to perform CouchDB queries without JavaScript or MapReduce. Mango Queries have a similar indexing speed advantage over JavaScript Queries than the Erlang Queries have (2x-10x faster indexing depending on doc size and system configuration). We recommend all new apps start using Mango as a default. Further details are available in the _find, _index and _explain API.
  • Mango selectors can be used in _changes feeds instead of JavaScript MapReduce filters. Mango has been tested to be up to an order of magnitude (10x) faster than JavaScript in this application.
  • Rewrite rules for URLs can be performed using JavaScript functions.
  • Multiple queries can be made of a view with a single HTTP request.
  • Views can be queried with sorting turned off ( sorted=false) for a performance boost.
  • The global changes feed has been enhanced. It is now resumable and persistent.
  • New endpoints added (documentation forthcoming):
    • /_membership shows all nodes in a cluster
    • /_bulk_get speeds up the replication protocol over low-latency connections
    • /_node/ api to access individual nodes’ configuration and compaction features
    • /_cluster_setup api to set up a cluster from scratch.
    • /_up api to signal health of a node to a load-balancer
    • /db/_local_docs and /db/_design_docs (similar to /db/_all_docs)
  • “Backend” interface on port 5986 used for specific cluster admin tasks. Of interest are the _nodes and _dbs databases visible only through this interface.
  • Support added for Erlang/OTP 17.x, 18.x and 19
  • New streamlined build system written for Unix-like systems and Microsoft Windows

15.1.2. Upgrade Notes

  • The update sequences returned by the /db/_changes feed are no longer integers. They can be any JSON value. Applications should treat them as opaque values and return them to CouchDB as-is.
  • Temporary views are no longer supported.
  • It is possible to have multiple replicator databases. replicator/db config option has been removed. Instead _replicator and any database names ending with the /_replicator suffix will be recognized as replicator databases by the system.
  • Note that the semantics of some API calls have changed due to the introduction of the clustering feature. Specifically, make note of the difference between receiving a 201 and a 202 when storing a document.
  • all_or_nothing is no longer supported by the bulk_docs API

15.1.3. Known Issues

All known issues filed against the 2.0 release are contained within the official CouchDB JIRA instance.

The following are some highlights of known issues for which fixes did not land in time for the 2.0.0 release:

  • COUCHDB-2980: The replicator (whether invoked via _replicate or a document stored in the _replicator database) understands two kinds of source and target:

    1. A URL (e.g., https://foo:bar@foo.com/db1), called a “remote” source or target
    2. A database name (e.g., db1), called a “local” source or target.

    Whenever the latter type is used, this refers to a local unclustered database, not a clustered one.

    In a future release we hope to support “local” source or target specs to clustered databases. For now, we recommend always using the URL format for both source and target specifications.

  • COUCHDB-3034: CouchDB will occasionally return 500 errors when multiple clients attempt to PUT or DELETE the same database concurrently.

  • COUCHDB-3119: Adding nodes to a cluster fails if the Erlang node name is not couchdb (of the form couchdb@hostname.)

  • COUCHDB-3050: Occasionally the dev/run script used for development purposes to start a local 3-node cluster will fail to start one or more nodes.

  • COUCHDB-2817: The compaction daemon will only compact views for shards that contain the design document.

  • COUCHDB-2804: The fast_view optimization is not enabled on the clustered interface.

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