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 = 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?

  @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}"
end

#to_s ⇒ Object 



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

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