# amqp-failover #

Add multi-server support with failover and fallback to the [amqp](https://github.com/ruby-amqp/amqp) gem. Failover is configured by providing multiple servers/configurations to `AMQP.start` or `AMQP.connect`. Both methods will still accept the same options input as they always have, they simply now support additional forms of options which when used, enables the failover features.


## Basic Usage ##

    require 'mq'
    require 'amqp/failover'
    opts = [{:port => 5672}, {:port => 5673}]
    AMQP.start(opts) do
      # code...
    end

By default the client will connect to `localhost:5672`, but if for any reason it can't connect, or looses connection to that server, it'll attempt to connect to `localhost:5673` instead.


## Options Formats ##

### Standard Non-Failover ###

Hash:

    opts = {:host => "hostname", :port => 5673}

URL:

    opts = "amqp://user:pass@hostname:5673/"

### With Failover ###

URLs

    opts = "amqp://localhost:5672/,amqp://localhost:5673/"

Array of Hashes:

    opts = [{:port => 5672}, {:port => 5673}]

Array of URLs:

    opts = ["amqp://localhost:5672/", "amqp://localhost:5673/"]

Specify AMQP servers and Failover options by passing a Hash containing a `:hosts` key with a value of either of the above three examples:

    opts = {:hosts => "amqp://localhost:5672/,amqp://localhost:5673/", :fallback => true}
    opts = {:hosts => [{:port => 5672}, {:port => 5673}], :fallback => true}
    opts = {:hosts => ["amqp://localhost:5672/", "amqp://localhost:5673/"], :fallback => true}

## Failover Options ##

* `:retry_timeout`, time to wait before retrying a specific AMQP config after failure.
* `:primary_config`, specify which of the supplied configurations is it the primary one. The default value is 0, the first item in the config array. Use 1 for the second and so on.
* `:fallback`, check for the return of the primary server, and fallback to it if and when it returns. WARNING: This currently calls `Process.exit` cause I haven't figured out a way to artificially kill the EM connection without the AMQP channels also being closed, which causes nothing to work even after EM connects to the primary server. It works for me cause dead workers are automatically relaunched with their default config.
* `:fallback_interval`, seconds between each check for original server if :fallback is true.
* `:selection`, not yet implemented.


## Notes ##

I would recommend you test the failover functionality in your own infrastructure before deploy to production, as this gem is still very much alpha/beta quality, and it does do a little bit of monkey patching to the amqp gem. That said, it there's a number of specs which should ensure things work as advertised, and nothing breaks. We are currently using it at Global Personals without any problems.


## Todo ##

* Figure out a sane way to fallback without having to kill the Ruby process.
* Better Readme/Documentation.
* Add option for next server selection on failover to be selected by random rather than next on the list.
* Convince get failover functionality merged in, or otherwise rewritten/added to the official AMQP gem.


## Note on Patches/Pull Requests ##
 
* Fork the project.
* Make your feature addition or bug fix.
* Add tests for it. This is important so I don't break it in a
  future version unintentionally.
* Commit, do not mess with rakefile, version, or history.
  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
* Send me a pull request. Bonus points for topic branches.


## Liccense and Copyright ##

Copyright (c) 2011 Jim Myhrberg & Global Personals, Ltd.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.