Module: Karafka::Core::Patches::Rdkafka::Bindings

Defined in:
lib/karafka/core/patches/rdkafka/bindings.rb

Overview

Extends Rdkafka::Bindings with some extra methods and updates callbacks that we intend to work with in a bit different way than rdkafka itself

Class Method Summary collapse

Class Method Details

.build_error_callback ⇒ FFI::Function

Returns overwritten callback function.

Returns:

  • (FFI::Function) —

    overwritten callback function



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# File 'lib/karafka/core/patches/rdkafka/bindings.rb', line 24

def build_error_callback
  FFI::Function.new(
    :void, %i[pointer int string pointer]
  ) do |client_ptr, err_code, reason, _opaque|
    return nil unless ::Rdkafka::Config.error_callback

    # Guard against a null client pointer. librdkafka can invoke the error callback
    # with a NULL `rd_kafka_t` (e.g. very early in client construction), and calling
    # `rd_kafka_name` on it dereferences the pointer and segfaults the whole process.
    # Mirrors the upstream `ErrorCallback`.
    name = client_ptr.null? ? nil : ::Rdkafka::Bindings.rd_kafka_name(client_ptr)

    # Resolve fatal errors to their underlying cause. `ERR__FATAL` is only a generic
    # marker; the real error code and description must be fetched from librdkafka via
    # `rd_kafka_fatal_error` (done by `RdkafkaError.build_fatal`). Without this the
    # callback would report the generic fatal code instead of the actual error.
    # Mirrors the upstream `ErrorCallback`.
    error = if err_code == ::Rdkafka::Bindings::RD_KAFKA_RESP_ERR__FATAL
      ::Rdkafka::RdkafkaError.build_fatal(
        client_ptr,
        fallback_error_code: err_code,
        fallback_message: reason,
        instance_name: name
      )
    else
      ::Rdkafka::RdkafkaError.new(err_code, broker_message: reason)
    end

    error.set_backtrace(caller)

    ::Rdkafka::Config.error_callback.call(name, error)
  end
end

.included(mod) ⇒ Object

Add extra methods that we need

Parameters:

  • mod (::Rdkafka::Bindings) —

    rdkafka bindings module



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# File 'lib/karafka/core/patches/rdkafka/bindings.rb', line 15

def included(mod)
  # Default rdkafka setup for errors doest not propagate client details, thus it always
  # publishes all the stuff for all rdkafka instances. We change that by providing
  # function that fetches the instance name, allowing us to have better notifications
  mod.send(:remove_const, :ErrorCallback)
  mod.const_set(:ErrorCallback, build_error_callback)
end