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It is no longer needed and is no longer maintained.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
Karafka Sidekiq Backend provides support for consuming (processing) received Kafka messages inside of Sidekiq workers.
Installations
Add this to your gemfile:
gem 'karafka-sidekiq-backend'
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 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:
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
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:
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 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.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:
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
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.