fts-elasticsearch

fts-elasticsearch is a Dovecot full-text search indexing plugin that uses ElasticSearch as a backend.

Dovecot communicates to ES using HTTP/JSON queries. It supports automatic indexing and searching of e-mail.

Requirements

• Dovecot 2.2+
• JSON-C
• ElasticSearch 6.x for your server
• Autoconf 2.53+

NOTE: You must add -Des.xcontent.strict_duplicate_detection=false to your Elasticsearch startup parameters. ES 7.0 will NOT be compatible with this plugin for now since this option will be deprecated.

Compiling

This plugin needs to compile against the Dovecot source for the version you intend to run it on. A dovecot-devel package is unfortunately insufficient as it does not include the required fts API header files.

You can provide the path to your source tree by passing --with-dovecot= to ./configure.

An example build may look like:

./autogen.sh
./configure --with-dovecot=/path/to/dovecot/src/root
make
make install

Configuration

In dovecot/conf.d/10-mail.conf:

mail_plugins = fts fts_elasticsearch

In dovecot/conf.d/90-plugins.conf:

plugin {
  fts = elasticsearch
  fts_elasticsearch = debug url=http://localhost:9200/
  fts_autoindex = yes
}

There are only two supported configuration parameters at the moment:

• url=<elasticsearch url> Required base URL
• debug Enables HTTP debugging

ElasticSearch Indicies

fts-elasticsearch creates an index per mail box with a hardcoded type of 'mail'. It creates one field for each field in the e-mail header and for the body.

An example of pushed data for a basic e-mail with no attachments:

{
	"uid": 3,
	"box": "f40efa2f8f44ad54424000006e8130ae",
	"Return-Path": "<josh@localhost.localdomain>",
	"X-Original-To": "josh",
	"Delivered-To": "josh@localhost.localdomain",
	"Received": "by localhost.localdomain (Postfix, from userid 1000) id 07DA3140314; Thu,  8 Jan 2015 00:20:05 +1100 (AEDT)",
	"Date": "Thu, 08 Jan 2015 00:20:05 +1100",
	"To": "josh@localhost.localdomain",
	"Subject": "Test #3",
	"User-Agent": "Heirloom mailx 12.5 7\/5\/10",
	"MIME-Version": "1.0",
	"Content-Type": "text\/plain; charset=us-ascii",
	"Content-Transfer-Encoding": "7bit",
	"Message-Id": "<20150107132005.07DA3140314@localhost.localdomain>",
	"From": "josh <josh@localhost.localdomain>",
	"body": "This is the body of test #3.\n"
}

An example search:

{
  "query": {
    "query_string": {
      "query": "*Dovecot*",
      "fields": [
        "subject"
      ]
    }
  },
  "fields": [
    "uid",
    "box"
  ]
}

TODO

There are a number of things left to be implemented:

• Rescan
• Optimisation (if any)
• Multiple mailbox lookup (for clients that call lookup_multi; need to find one)

Background

Dovecot currently supports two primary full text search indexing plugins fts-solr and fts-squat. I wanted to use an FTS service that I already had set-up and that wasn't quite as heavy as Solr, primarily to consolidate infrastructure and to focus resources on optimising our ES instances.

Thanks

This plugin borrows heavily from dovecot itself particularly for the automatic detection of dovecont-config (see m4/dovecot.m4). The fts-solr and fts-squat plugins were also used as reference material for understanding the Dovecot FTS API.