The CouchDB River allows to automatically index couchdb and make it searchable using the excellent _changes stream couchdb provides. Setting it up is as simple as executing the following against elasticsearch:

curl -XPUT 'localhost:9200/_river/my_db/_meta' -d '{
    "type" : "couchdb",
    "couchdb" : {
        "host" : "localhost",
        "port" : 5984,
        "db" : "my_db",
        "filter" : null
    },
    "index" : {
        "index" : "my_db",
        "type" : "my_db",
        "bulk_size" : "100",
        "bulk_timeout" : "10ms"
    }
}'

This call will create a river that uses the _changes stream to index all data within couchdb. Moreover, any “future” changes will automatically be indexed as well, making your search index and couchdb synchronized at all times.

The couchdb river is provided as a plugin and can be installed using plugin -install river-couchdb.

On top of that, in case of a failover, the couchdb river will automatically be started on another elasticsearch node, and continue indexing from the last indexed seq.

Bulking

Bulking is automatically done in order to speed up the indexing process. If within the specified bulk_timeout more changes are detected, changes will be bulked up to bulk_size before they are indexed.

Filtering

The `changes` stream allows to provide a filter with parameters that will be used by couchdb to filter the stream of changes. Here is how ti can be configured:

{
    "couchdb" : {
        "filter" : "test",
        "filter_params" : {
            "param1" : "value1",
            "param2" : "value2"
        }
    }
}

Script Filters

Filtering can also be performed by providing a script (default to JavaScript) that will further process each changed item within the changes stream. The json provided to the script is under a var called ctx with the relevant seq stream change (for example, ctx.doc will refer to the document, or ctx.deleted is the flag if its deleted or not).

Note, this feature requires the `lang-javascript` plugin.

The ctx.doc can be changed and its value can will be indexed (assuming its not a deleted change). Also, if ctx.ignore is set to true, the change seq will be ignore and not applied.

Other possible values that can be set are ctx.index to control the index name to index the doc into, ctx.type to control the (mapping) type to index into, ctx._parent and ctx._routing.

Here is an example setting that adds `field1` with value `value1` to all docs:

{
    "type" : "couchdb",
    "couchdb" : {
        "script" : "ctx.doc.field1 = 'value1'"
    }
}