Karafka Sidekiq Backend
Karafka Sidekiq Backend provides support for consuming (processing) received Kafka messages inside of Sidekiq workers.
Add this to your gemfile:
and create a file called
application_worker.rb inside of your
app/workers directory, that looks like that:
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
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:
class App < Karafka::App setup do |config| config.backend = :sidekiq # Other config options... end end
or on a per topic level:
App.routes.draw do consumer_group :videos_consumer do topic :binary_video_details do consumer Videos::DetailsConsumer worker Workers::DetailsWorker interchanger Interchangers::MyCustomInterchanger 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.
There are two options you can set inside of the
|worker||Class||Name of a worker class that we want to use to schedule perform code|
|interchanger||Class||Name of an interchanger class that we want to use to pass the incoming data to Sidekiq|
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:
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.
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 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:
App.routes.draw do consumer_group :videos_consumer do topic :binary_video_details do consumer Videos::DetailsConsumer interchanger Interchangers::MyCustomInterchanger 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:
class Base64Interchanger class << self def encode(params_batch) # Note, that you need to cast the params_batch to an array in order to get it work # in sidekiq later Base64.encode64(Marshal.dump(params_batch.to_a)) end def decode(params_string) Marshal.load(Base64.decode64(params_string)) end end end
Warning: if you decide to use slow interchangers, they might significantly slow down Karafka.
Note on contributions
First, thank you for considering contributing to Karafka! It's people like you that make the open source community such a great community!
Each pull request must pass all the RSpec specs and meet our quality requirements.
To check if everything is as it should be, we use Coditsu that combines multiple linters and code analyzers for both code and documentation. Once you're done with your changes, submit a pull request.
Coditsu will automatically check your work against our quality standards. You can find your commit check results on the builds page of Karafka Sidekiq Backend repository.