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https://github.com/karafka/sidekiq-backend

[Unmaintained] Karafka Sidekiq backend for background messages processing
https://github.com/karafka/sidekiq-backend

kafka karafka karafka-application karafka-framework ruby ruby-kafka rubygem

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[Unmaintained] Karafka Sidekiq backend for background messages processing

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# Karafka Sidekiq Backend



## Deprecation notice



This backend was designed to compensate for lack of multi-threading in Karafka. Karafka `2.0` **is** multi-threaded.



It is **no longer needed** and is **no longer** maintained.



## About



[![Build Status](https://github.com/karafka/sidekiq-backend/workflows/ci/badge.svg)](https://github.com/karafka/sidekiq-backend/actions?query=workflow%3Aci)

[![Gem Version](https://badge.fury.io/rb/karafka-sidekiq-backend.svg)](http://badge.fury.io/rb/karafka-sidekiq-backend)

[![Join the chat at https://slack.karafka.io](https://raw.githubusercontent.com/karafka/misc/master/slack.svg)](https://slack.karafka.io)



[Karafka Sidekiq Backend](https://github.com/karafka/sidekiq-backend) provides support for consuming (processing) received Kafka messages inside of Sidekiq workers.



## Installations



Add this to your gemfile:



```ruby

gem 'karafka-sidekiq-backend'

```



and create a file called ```application_worker.rb``` inside of your ```app/workers``` directory, that looks like that:



```ruby

class ApplicationWorker < Karafka::BaseWorker

end

```



and you are ready to go. Karafka Sidekiq Backend integrates with Karafka automatically



**Note**: You can name your application worker base class with any name you want. The only thing that is required is a direct inheritance from the ```Karafka::BaseWorker``` class.



## Usage



If you want to process messages with Sidekiq backend, you need to tell this to Karafka.



To do so, you can either configure that in a configuration block:



```ruby

class App < Karafka::App

  setup do |config|

    config.backend = :sidekiq

    # Other config options...

  end

end

```



or on a per topic level:



```ruby

App.routes.draw do

  consumer_group :videos_consumer do

    topic :binary_video_details do

      backend :sidekiq

      consumer Videos::DetailsConsumer

      worker Workers::DetailsWorker

      interchanger Interchangers::MyCustomInterchanger.new

    end

  end

end

```



You don't need to do anything beyond that. Karafka will know, that you want to run your consumer's ```#consume``` method in a background job.



## Configuration



There are two options you can set inside of the ```topic``` block:



| Option       | Value type | Description                                                                                                       |

|--------------|------------|-------------------------------------------------------------------------------------------------------------------|

| worker       | Class      | Name of a worker class that we want to use to schedule perform code                                               |

| interchanger | Instance   | Instance of an interchanger class that we want to use to pass the incoming data to Sidekiq                        |



### Workers



Karafka by default will build a worker that will correspond to each of your consumers (so you will have a pair - consumer and a worker). All of them will inherit from ```ApplicationWorker``` and will share all its settings.



To run Sidekiq you should have sidekiq.yml file in *config* folder. The example of ```sidekiq.yml``` file will be generated to config/sidekiq.yml.example once you run ```bundle exec karafka install```.



However, if you want to use a raw Sidekiq worker (without any Karafka additional magic), or you want to use SidekiqPro (or any other queuing engine that has the same API as Sidekiq), you can assign your own custom worker:



```ruby

topic :incoming_messages do

  consumer MessagesConsumer

  worker MyCustomWorker

end

```



Note that even then, you need to specify a consumer that will schedule a background task.



Custom workers need to provide a ```#perform_async``` method. It needs to accept two arguments:



 - ```topic_id``` - first argument is a current topic id from which a given message comes

 - ```params_batch``` - all the params that came from Kafka + additional metadata. This data format might be changed if you use custom interchangers. Otherwise, it will be an instance of Karafka::Params::ParamsBatch.



**Note**: If you use custom interchangers, keep in mind, that params inside params batch might be in two states: parsed or unparsed when passed to #perform_async. This means, that if you use custom interchangers and/or custom workers, you might want to look into Karafka's sources to see exactly how it works.



### Interchangers



Custom interchangers target issues with non-standard (binary, etc.) data that we want to store when we do ```#perform_async```. This data might be corrupted when fetched in a worker (see [this](https://github.com/karafka/karafka/issues/30) issue). With custom interchangers, you can encode/compress data before it is being passed to scheduling and decode/decompress it when it gets into the worker.



To specify the interchanger for a topic, specify the interchanger inside routes like this:



```ruby

App.routes.draw do

  consumer_group :videos_consumer do

    topic :binary_video_details do

      consumer Videos::DetailsConsumer

      interchanger Interchangers::MyCustomInterchanger.new

    end

  end

end

```

Each custom interchanger should define `encode` to encode params before they get stored in Redis, and `decode` to convert the params to hash format, as shown below:



```ruby

class Base64Interchanger < ::Karafka::Interchanger

  def encode(params_batch)

    Base64.encode64(Marshal.dump(super))

  end



  def decode(params_string)

    Marshal.load(Base64.decode64(super))

  end

end



```



**Warning**: if you decide to use slow interchangers, they might significantly slow down Karafka.



## References



* [Karafka framework](https://github.com/karafka/karafka)

* [Karafka Sidekiq Backend Actions CI](https://github.com/karafka/sidekiq-backend/actions?query=workflow%3Aci)

* [Karafka Sidekiq Backend Coditsu](https://app.coditsu.io/karafka/repositories/karafka-sidekiq-backend)



## Note on contributions



First, thank you for considering contributing to the Karafka ecosystem! It's people like you that make the open source community such a great community!



Each pull request must pass all the RSpec specs, integration tests and meet our quality requirements.



Fork it, update and wait for the Github Actions results.