CouchRest::Changes - keeping track of changes to your couch

CouchRest::Changes let's you observe a couch database for changes and react upon them.

Following the changes of a couch is as easy as

users = CouchRest::Changes.new('users')

Callbacks can be defined in blocks:

users.created do |hash|
  puts "A new user was created with the id: #{hash[:id]}"
end

To start listening just call

users.listen

This program is copyright 2015 LEAP Encryption Access Project. It distributed under the same license as CouchRest (Apache License, Version 2.0 http://www.apache.org/licenses/).

Installation

Just add couchrest_changes to your Gemfile.

Configuration

couchrest_changes can be configured through CouchRest::Changes::Config

The default options are similar to the ones used by CouchRest::Model:

# couch connection configuration
connection:
  protocol: "http"
  host: "localhost"
  port: 5984
  username: ~
  password: ~
  prefix: ""
  suffix: ""
  netrc: ""

# directory to store the last processed record sequence
# so we can resume after a restart:
seq_dir: "/var/run/couch_changes"

# Configure log_file like this if you want to log to a file instead of syslog:
# log_file: "/var/log/couch_changes.log"
log_level: debug

options:
  your_own_options: "go here"

Normally, CouchRest leaks the CouchDB authentication credentials in the process list. If present, the netrc configuration value will allow CouchRest::Changes to use the netrc file and keep the credentials out of the process list.

Running Tests

In order for the CouchRest::Changes tests to run, a local CouchDB must be running in "admin party" mode. The tests themselves require that there is no admin party, but the tests will correctly disable the admin party (by creating a super admin called 'superadmin' with password 'secret').

After the tests have run, the admin party is restored. If something goes wrong, you should remove the superadmin line at the end of /etc/couchdb/local.ini and restart couchdb.

Examples

See tapicero for a daemon that uses CouchRest::Changes. Historically CouchRest::Changes was extracted from tapicero.

Known Issues

• CouchRest will miss the first change in a continuous feed. https://github.com/couchrest/couchrest/pull/104 has a fix. You might want to monkeypatch it.

Changes

0.2.0

UPGRADING: the configuration 'seq_file' is no longer used, but 'seq_dir' is required.

• hide password and username from process list by monkeypatching couchrest.
• support for listening on changes to multiple databases (new sequence file format, so sequence processing will start from scratch when upgrading).
• automatically disable admin party when running tests

0.1.1

• recover gracefully if couchdb returns an invalid sequence (as bigcouchd does sometimes)