Beholder

Beholder is an agent written in Python for twemproxy to work with a redis sentinel to provide support for failover.

Beholder's purpose is to extend the HA capabilities of twemproxy even after a redis node has failed.

In order to accomplish this, beholder is continuously monitoring the +switch-master event, then it will update twemproxy configuration files and restart the resource.

Dependencies

Beholder use redis-py and pyyaml, so the first step is install the dependencies:

$ pip install redis
$ pip install pyyaml

If you want to install python yaml system-wide in linux, you can also use a package manager, like:

$ sudo apt-get install python-yaml
$ sudo yum install python-yaml

Installation

The follow installation steps are the default ones, feel free to change any path.

$ sudo cp src/beholder.py /usr/local/bin/beholder.py
$ sudo cp conf/beholder.yml /etc/nutcracker/beholder.yml
$ sudo cp scripts/beholder.init /etc/init.d/beholder
$ sudo chmod 775 /etc/init.d/beholder
$ sudo chkconfig --add /etc/init.d/beholder
$ sudo chkconfig beholder on
$ sudo service beholder start

Configuration

Beholder can be configured through a YAML file beholder.yml.

beholder:
  log_file: "/var/log/beholder.log"
  connect_retry_count: -1 # -1 to unlimited
  connect_retry_interval: 1000 # Milliseconds

redis:
  sentinel_ip: "127.0.0.1"
  sentinel_port: 26379

twemproxy:
  config_file: "/etc/nutcracker/nutcracker.yml"
  restart_command: "/etc/init.d/nutcracker restart"

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0

See LICENSE.md