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https://github.com/JustinLove/autoscaler

Start/stop Sidekiq workers on Heroku
https://github.com/JustinLove/autoscaler

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Start/stop Sidekiq workers on Heroku

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# Sidekiq Heroku Autoscaler



[Sidekiq](https://github.com/mperham/sidekiq) performs background jobs.  While its threading model allows it to scale easier than worker-pre-process background systems, people running test or lightly loaded systems on [Heroku](http://www.heroku.com/) still want to scale down to zero to avoid racking up charges.



## Requirements



Tested on Ruby 2.1.7 and Heroku Cedar stack.



## Installation



    gem install autoscaler



## Getting Started



This gem uses the [Heroku Platform-Api](https://github.com/heroku/platform-api) gem, which requires an OAuth token from Heroku.  It will also need the heroku app name.  By default, these are specified through environment variables.  You can also pass them to `HerokuPlatformScaler` explicitly.



    AUTOSCALER_HEROKU_ACCESS_TOKEN=.....

    AUTOSCALER_HEROKU_APP=....



Install the middleware in your `Sidekiq.configure_` blocks



    require 'autoscaler/sidekiq'

    require 'autoscaler/heroku_platform_scaler'



    Sidekiq.configure_client do |config|

      config.client_middleware do |chain|

        chain.add Autoscaler::Sidekiq::Client, 'default' => Autoscaler::HerokuPlatformScaler.new

      end

    end



    Sidekiq.configure_server do |config|

      config.server_middleware do |chain|

        chain.add(Autoscaler::Sidekiq::Server, Autoscaler::HerokuPlatformScaler.new, 60) # 60 second timeout

      end

    end



## Limits and Challenges



- HerokuPlatformScaler includes an attempt at current-worker cache that may be overcomplication, and doesn't work very well on the server

- Multiple scale-down loops may be started, particularly if there are multiple jobs queued when the servers comes up.  Heroku seems to handle multiple scale-down commands well.

- The scale-down monitor is triggered on job completion (and server middleware is only run around jobs), so if the server never processes any jobs, it won't turn off.

- The retry and schedule lists are considered - if you schedule a long-running task, the process will not scale-down.

- If background jobs trigger jobs in other scaled processes, please note you'll need `config.client_middleware` in your `Sidekiq.configure_server` block in order to scale-up.

- Exceptions while calling the Heroku API are caught and printed by default.  See `HerokuPlatformScaler#exception_handler` to override



## Experimental



### Strategies



You can pass a scaling strategy object instead of the timeout to the server middleware.  The object (or lambda) should respond to `#call(system, idle_time)` and return the desired number of workers.  See `lib/autoscaler/binary_scaling_strategy.rb` for an example.



### Initial Workers



`Client#set_initial_workers` to start workers on main process startup; typically:



    Autoscaler::Sidekiq::Client.add_to_chain(chain, 'default' => heroku).set_initial_workers



### Working caching



    scaler.counter_cache = Autoscaler::CounterCacheRedis.new(Sidekiq.method(:redis))



## Tests



The project is setup to run RSpec with Guard.  It expects a redis instance on a custom port, which is started by the Guardfile.



The HerokuPlatformScaler is not tested by default because it makes live API requests.  Specify `AUTOSCALER_HEROKU_APP` and `AUTOSCALER_HEROKU_ACCESS_TOKEN` on the command line, and then watch your app's logs.



    AUTOSCALER_HEROKU_APP=... AUTOSCALER_HEROKU_ACCESS_TOKEN=... guard

    heroku logs --app ...



## Authors



Justin Love, [@wondible](http://twitter.com/wondible), [https://github.com/JustinLove](https://github.com/JustinLove)



### Contributors



- Benjamin Kudria [https://github.com/bkudria](https://github.com/bkudria)

- claudiofullscreen [https://github.com/claudiofullscreen](https://github.com/claudiofullscreen)

- Fix Peña [https://github.com/fixr](https://github.com/fixr)

- Gabriel Givigier Guimarães [https://github.com/givigier](https://github.com/givigier)

- Matt Anderson [https://github.com/tonkapark](https://github.com/tonkapark)

- Thibaud Guillaume-Gentil [https://github.com/jilion](https://github.com/jilion)



## Licence



Released under the [MIT license](http://www.opensource.org/licenses/mit-license.php).