Class: Kafka::Connection

Inherits:
Object
  • Object
show all
Defined in:
lib/kafka/connection.rb

Overview

A connection to a single Kafka broker.

Usually you’ll need a separate connection to each broker in a cluster, since most requests must be directed specifically to the broker that is currently leader for the set of topic partitions you want to produce to or consume from.

## Instrumentation

Connections emit a ‘request.connection.kafka` notification on each request. The following keys will be found in the payload:

  • ‘:api` — the name of the API being invoked.

  • ‘:request_size` — the number of bytes in the request.

  • ‘:response_size` — the number of bytes in the response.

The notification also includes the duration of the request.

Constant Summary collapse

SOCKET_TIMEOUT = 
10
CONNECT_TIMEOUT = 
10
IDLE_TIMEOUT =

Time after which an idle connection will be reopened.

60 * 5

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(host:, port:, client_id:, logger:, instrumenter:, connect_timeout: nil, socket_timeout: nil, ssl_context: nil) ⇒ Connection

Opens a connection to a Kafka broker.

Parameters:

  • host (String) —

    the hostname of the broker.

  • port (Integer) —

    the port of the broker.

  • client_id (String) —

    the client id is a user-specified string sent in each request to help trace calls and should logically identify the application making the request.

  • logger (Logger) —

    the logger used to log trace messages.

  • connect_timeout (Integer) (defaults to: nil) —

    the socket timeout for connecting to the broker. Default is 10 seconds.

  • socket_timeout (Integer) (defaults to: nil) —

    the socket timeout for reading and writing to the broker. Default is 10 seconds.



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# File 'lib/kafka/connection.rb', line 53

def initialize(host:, port:, client_id:, logger:, instrumenter:, connect_timeout: nil, socket_timeout: nil, ssl_context: nil)
  @host, @port, @client_id = host, port, client_id
  @logger = TaggedLogger.new(logger)
  @instrumenter = instrumenter

  @connect_timeout = connect_timeout || CONNECT_TIMEOUT
  @socket_timeout = socket_timeout || SOCKET_TIMEOUT
  @ssl_context = ssl_context
end

Instance Attribute Details

#decoder ⇒ Object (readonly)

Returns the value of attribute decoder.



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# File 'lib/kafka/connection.rb', line 37

def decoder
  @decoder
end

#encoder ⇒ Object (readonly)

Returns the value of attribute encoder.



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# File 'lib/kafka/connection.rb', line 36

def encoder
  @encoder
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/kafka/connection.rb', line 71

def close
  @logger.debug "Closing socket to #{to_s}"

  @socket.close if @socket
end

#open? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/kafka/connection.rb', line 67

def open?
  !@socket.nil? && !@socket.closed?
end

#send_request(request) ⇒ Object

Sends a request over the connection.

Parameters:

  • request (#encode, #response_class) —

    the request that should be encoded and written.

Returns:

  • (Object) —

    the response.



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# File 'lib/kafka/connection.rb', line 83

def send_request(request)
  api_name = Protocol.api_name(request.api_key)

  # Default notification payload.
  notification = {
    broker_host: @host,
    api: api_name,
    request_size: 0,
    response_size: 0,
  }

  raise IdleConnection if idle?

  @logger.push_tags(api_name)
  @instrumenter.instrument("request.connection", notification) do
    open unless open?

    @correlation_id += 1

    @logger.debug "Sending #{api_name} API request #{@correlation_id} to #{to_s}"

    write_request(request, notification)

    response_class = request.response_class
    response = wait_for_response(response_class, notification) unless response_class.nil?

    @last_request = Time.now

    response
  end
rescue SystemCallError, EOFError, IOError => e
  close

  raise ConnectionError, "Connection error #{e.class}: #{e}"
ensure
  @logger.pop_tags
end

#to_s ⇒ Object 



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# File 'lib/kafka/connection.rb', line 63

def to_s
  "#{@host}:#{@port}"
end