Module: NATS

Defined in:
lib/nats/version.rb,
lib/nats/nuid.rb,
lib/nats/client.rb

Overview

Copyright 2010-2018 The NATS Authors Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Defined Under Namespace

Classes: AuthError, ClientError, ConnectError, Error, MonotonicTime, NUID, ServerError

Constant Summary collapse

DEFAULT_PORT =
4222
DEFAULT_URI =
"nats://localhost:#{DEFAULT_PORT}".freeze
MAX_RECONNECT_ATTEMPTS =
10
RECONNECT_TIME_WAIT =
2
MAX_PENDING_SIZE =
32768
FAST_PRODUCER_THRESHOLD =

Maximum outbound size per client to trigger FP, 20MB

(10*1024*1024)
DEFAULT_PING_INTERVAL =

Ping intervals

120
DEFAULT_PING_MAX =
2
DEFAULT_DRAIN_TIMEOUT =

Drain mode support

30
MSG =

Protocol

/\AMSG\s+([^\s]+)\s+([^\s]+)\s+(([^\s]+)[^\S\r\n]+)?(\d+)\r\n/i
OK =

:nodoc:

/\A\+OK\s*\r\n/i
ERR =

:nodoc:

/\A-ERR\s+('.+')?\r\n/i
PING =

:nodoc:

/\APING\s*\r\n/i
PONG =

:nodoc:

/\APONG\s*\r\n/i
INFO =

:nodoc:

/\AINFO\s+([^\r\n]+)\r\n/i
UNKNOWN =

:nodoc:

/\A(.*)\r\n/
CR_LF =

Responses

("\r\n".freeze)
CR_LF_SIZE =

:nodoc:

(CR_LF.bytesize)
PING_REQUEST =

:nodoc:

("PING#{CR_LF}".freeze)
PONG_RESPONSE =

:nodoc:

("PONG#{CR_LF}".freeze)
SUB_OP =

:nodoc:

('SUB'.freeze)
EMPTY_MSG =

:nodoc:

(''.freeze)
SUB =

Used for future pedantic Mode

/^([^\.\*>\s]+|>$|\*)(\.([^\.\*>\s]+|>$|\*))*$/
SUB_NO_WC =

:nodoc:

/^([^\.\*>\s]+)(\.([^\.\*>\s]+))*$/
AWAITING_CONTROL_LINE =

Parser

1
AWAITING_MSG_PAYLOAD =

:nodoc:

2
VERSION =

NOTE: These are all announced to the server on CONNECT

"0.10.0".freeze
LANG =
RUBY_ENGINE
PROTOCOL_VERSION =
1

Class Attribute Summary collapse

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Class Attribute Details

.clientObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 91

def client
  @client
end

.close_cbObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 92

def close_cb
  @close_cb
end

.disconnect_cbObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 92

def disconnect_cb
  @disconnect_cb
end

.err_cbObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 91

def err_cb
  @err_cb
end

.err_cb_overriddenObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 91

def err_cb_overridden
  @err_cb_overridden
end

.reactor_was_runningObject (readonly) Also known as: reactor_was_running?

:nodoc:



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# File 'lib/nats/client.rb', line 91

def reactor_was_running
  @reactor_was_running
end

.reconnect_cbObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 92

def reconnect_cb
  @reconnect_cb
end

Instance Attribute Details

#bytes_receivedObject (readonly)

Returns the value of attribute bytes_received



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# File 'lib/nats/client.rb', line 445

def bytes_received
  @bytes_received
end

#bytes_sentObject (readonly)

Returns the value of attribute bytes_sent



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# File 'lib/nats/client.rb', line 445

def bytes_sent
  @bytes_sent
end

#close_cbObject (readonly)

Returns the value of attribute close_cb



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# File 'lib/nats/client.rb', line 446

def close_cb
  @close_cb
end

#closingObject (readonly) Also known as: closing?

:nodoc



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# File 'lib/nats/client.rb', line 444

def closing
  @closing
end

#connect_cbObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 443

def connect_cb
  @connect_cb
end

#connectedObject (readonly) Also known as: connected?

:nodoc:



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# File 'lib/nats/client.rb', line 443

def connected
  @connected
end

#disconnect_cbObject (readonly)

Returns the value of attribute disconnect_cb



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# File 'lib/nats/client.rb', line 446

def disconnect_cb
  @disconnect_cb
end

#drainingObject (readonly) Also known as: draining?

:nodoc



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# File 'lib/nats/client.rb', line 444

def draining
  @draining
end

#err_cbObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 443

def err_cb
  @err_cb
end

#err_cb_overriddenObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 443

def err_cb_overridden
  @err_cb_overridden
end

#msgs_receivedObject (readonly)

Returns the value of attribute msgs_received



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# File 'lib/nats/client.rb', line 445

def msgs_received
  @msgs_received
end

#msgs_sentObject (readonly)

Returns the value of attribute msgs_sent



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# File 'lib/nats/client.rb', line 445

def msgs_sent
  @msgs_sent
end

#optionsObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 444

def options
  @options
end

#pingsObject (readonly)

Returns the value of attribute pings



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# File 'lib/nats/client.rb', line 445

def pings
  @pings
end

#pongs_receivedObject (readonly)

:nodoc:



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# File 'lib/nats/client.rb', line 443

def pongs_received
  @pongs_received
end

#reconnectingObject (readonly) Also known as: reconnecting?

:nodoc



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# File 'lib/nats/client.rb', line 444

def reconnecting
  @reconnecting
end

#server_infoObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 444

def server_info
  @server_info
end

#server_poolObject (readonly)

:nodoc



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# File 'lib/nats/client.rb', line 444

def server_pool
  @server_pool
end

Class Method Details

.clear_clientObject

:nodoc:



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# File 'lib/nats/client.rb', line 400

def clear_client # :nodoc:
  @client = nil
end

.connect(uri = nil, opts = {}, &blk) ⇒ NATS

Create and return a connection to the server with the given options. The optional block will be called when the connection has been completed.

Examples:

Connect to local NATS server.

NATS.connect do |nc|
  # ...
end

Setting custom server URI to connect.

NATS.connect("nats://localhost:4222") do |nc|
  # ...
end

Setting username and password to authenticate.

NATS.connect("nats://user:password@localhost:4222") do |nc|
  # ...
end

Specifying explicit list of servers via options.

NATS.connect(servers: ["nats://127.0.0.1:4222","nats://127.0.0.1:4223","nats://127.0.0.1:4224"]) do |nc|
  # ...
end

Using comma separated array to define list of servers.

NATS.connect("nats://localhost:4223,nats://localhost:4224") do |nc|
  # ...
end

Only specifying endpoint uses NATS default scheme and port.

NATS.connect("demo.nats.io") do |nc|
  # ...
end

Setting infinite reconnect retries with 2 seconds back off against custom URI.

NATS.connect("demo.nats.io:4222", max_reconnect_attempts: -1, reconnect_time_wait: 2) do |nc|
  # ...
end

Parameters:

  • uri (String) (defaults to: nil)

    The URI or comma separated list of URIs of NATS servers to connect to.

  • opts (Hash) (defaults to: {})
  • &blk (Block)

    called when the connection is completed. Connection will be passed to the block.

Options Hash (opts):

  • :uri (String|URI)

    The URI to connect to, example nats://localhost:4222

  • :reconnect (Boolean)

    Boolean that can be used to suppress reconnect functionality.

  • :debug (Boolean)

    Boolean that can be used to output additional debug information.

  • :verbose (Boolean)

    Boolean that is sent to server for setting verbose protocol mode.

  • :pedantic (Boolean)

    Boolean that is sent to server for setting pedantic mode.

  • :ssl (Boolean)

    Boolean that is sent to server for setting TLS/SSL mode.

  • :tls (Hash)

    Map of options for configuring secure connection handled to EM#start_tls directly.

  • :max_reconnect_attempts (Integer)

    Integer that can be used to set the max number of reconnect tries

  • :reconnect_time_wait (Integer)

    Integer that can be used to set the number of seconds to wait between reconnect tries

  • :ping_interval (Integer)

    Integer that can be used to set the ping interval in seconds.

  • :max_outstanding_pings (Integer)

    Integer that can be used to set the max number of outstanding pings before declaring a connection closed.

Returns:

  • (NATS)

    connection to the server.



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# File 'lib/nats/client.rb', line 150

def connect(uri=nil, opts={}, &blk)
  case uri
  when String
    opts[:uri] = process_uri(uri)
  when Hash
    opts = uri
  end

  # Defaults
  opts[:verbose] = false if opts[:verbose].nil?
  opts[:pedantic] = false if opts[:pedantic].nil?
  opts[:reconnect] = true if opts[:reconnect].nil?
  opts[:ssl] = false if opts[:ssl].nil?
  opts[:max_reconnect_attempts] = MAX_RECONNECT_ATTEMPTS if opts[:max_reconnect_attempts].nil?
  opts[:reconnect_time_wait] = RECONNECT_TIME_WAIT if opts[:reconnect_time_wait].nil?
  opts[:ping_interval] = DEFAULT_PING_INTERVAL if opts[:ping_interval].nil?
  opts[:max_outstanding_pings] = DEFAULT_PING_MAX if opts[:max_outstanding_pings].nil?
  opts[:drain_timeout] = DEFAULT_DRAIN_TIMEOUT if opts[:drain_timeout].nil?

  # Override with ENV
  opts[:uri] ||= ENV['NATS_URI'] || DEFAULT_URI
  opts[:verbose] = ENV['NATS_VERBOSE'].downcase == 'true' unless ENV['NATS_VERBOSE'].nil?
  opts[:pedantic] = ENV['NATS_PEDANTIC'].downcase == 'true' unless ENV['NATS_PEDANTIC'].nil?
  opts[:debug] = ENV['NATS_DEBUG'].downcase == 'true' unless ENV['NATS_DEBUG'].nil?
  opts[:reconnect] = ENV['NATS_RECONNECT'].downcase == 'true' unless ENV['NATS_RECONNECT'].nil?
  opts[:fast_producer_error] = ENV['NATS_FAST_PRODUCER'].downcase == 'true' unless ENV['NATS_FAST_PRODUCER'].nil?
  opts[:ssl] = ENV['NATS_SSL'].downcase == 'true' unless ENV['NATS_SSL'].nil?
  opts[:max_reconnect_attempts] = ENV['NATS_MAX_RECONNECT_ATTEMPTS'].to_i unless ENV['NATS_MAX_RECONNECT_ATTEMPTS'].nil?
  opts[:reconnect_time_wait] = ENV['NATS_RECONNECT_TIME_WAIT'].to_i unless ENV['NATS_RECONNECT_TIME_WAIT'].nil?
  opts[:name] ||= ENV['NATS_CONNECTION_NAME']
  opts[:no_echo] ||= ENV['NATS_NO_ECHO'] || false
  opts[:ping_interval] = ENV['NATS_PING_INTERVAL'].to_i unless ENV['NATS_PING_INTERVAL'].nil?
  opts[:max_outstanding_pings] = ENV['NATS_MAX_OUTSTANDING_PINGS'].to_i unless ENV['NATS_MAX_OUTSTANDING_PINGS'].nil?
  opts[:drain_timeout] ||= ENV['NATS_DRAIN_TIMEOUT'].to_i unless ENV['NATS_DRAIN_TIMEOUT'].nil?

  uri = opts[:uris] || opts[:servers] || opts[:uri]

  if opts[:tls]
    case
    when opts[:tls][:ca_file]
      # Ensure that the file exists before going further
      # in order to report configuration errors during
      # connect synchronously.
      if !File.readable?(opts[:tls][:ca_file])
        raise(Error, "TLS Verification is enabled but ca_file %s is not readable" % opts[:tls][:ca_file])
      end

      # Certificate is supplied so assume we mean verification by default,
      # but still allow disabling explicitly by setting to false.
      opts[:tls][:verify_peer] ||= true
    when (opts[:tls][:verify_peer] && !opts[:tls][:ca_file])
      raise(Error, "TLS Verification is enabled but ca_file is not set")
    else
      # Otherwise, disable verifying peer by default,
      # thus never reaching EM#ssl_verify_peer
      opts[:tls][:verify_peer] = false
    end

    # Allow overriding directly but default to those which server supports.
    opts[:tls][:ssl_version] ||= %w(tlsv1 tlsv1_1 tlsv1_2)
    opts[:tls][:protocols]   ||= %w(tlsv1 tlsv1_1 tlsv1_2)
  end

  # If they pass an array here just pass along to the real connection, and use first as the first attempt..
  # Real connection will do proper walk throughs etc..
  unless uri.nil?
    uris = uri.kind_of?(Array) ? uri : [uri]
    uris.shuffle! unless opts[:dont_randomize_servers]
    u = uris.first
    @uri = u.is_a?(URI) ? u.dup : URI.parse(u)
  end

  @err_cb = proc { |e| raise e } unless err_cb
  @close_cb = proc { } unless close_cb
  @disconnect_cb = proc { } unless disconnect_cb

  client = EM.connect(@uri.host, @uri.port, self, opts)
  client.on_connect(&blk) if blk
  return client
end

.connected?Boolean

Returns Connected state

Returns:

  • (Boolean)

    Connected state



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# File 'lib/nats/client.rb', line 279

def connected?
  return false unless client
  client.connected?
end

.connected_serverURI

Returns Connected server

Returns:

  • (URI)

    Connected server



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# File 'lib/nats/client.rb', line 273

def connected_server
  return nil unless client
  client.connected_server
end

.create_inboxString

Returns a subject that can be used for “directed” communications.

Returns:



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# File 'lib/nats/client.rb', line 367

def create_inbox
  "_INBOX.#{SecureRandom.hex(13)}"
end

.drain(&blk) ⇒ Object

Drain gracefully disconnects from the server, letting subscribers process pending messages already sent by server and optionally calls the associated block.

Parameters:

  • &blk (Block)

    called when drain is done and connection is closed.



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# File 'lib/nats/client.rb', line 266

def drain(&blk)
  if (client and !client.draining? and (client.connected? || client.reconnecting?))
    client.drain { blk.call if blk }
  end
end

.draining?Boolean

Returns Draining state

Returns:

  • (Boolean)

    Draining state



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# File 'lib/nats/client.rb', line 291

def draining?
  return false unless client
  client.draining?
end

.flush(*args, &blk) ⇒ Object

Flushes all messages and subscriptions in the default connection

See Also:



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# File 'lib/nats/client.rb', line 373

def flush(*args, &blk)
  (@client ||= connect).flush(*args, &blk)
end

.on_close(&callback) ⇒ Object

Set the default on_closed callback.

Parameters:

  • &callback (Block)

    called when will reach a state when will no longer be connected.



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# File 'lib/nats/client.rb', line 330

def on_close(&callback)
  @close_cb = callback
  @client.on_close(&callback) unless @client.nil?
end

.on_disconnect(&callback) ⇒ Object

Set the default on_disconnect callback.

Parameters:

  • &callback (Block)

    called whenever client disconnects from a server.



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# File 'lib/nats/client.rb', line 323

def on_disconnect(&callback)
  @disconnect_cb = callback
  @client.on_disconnect(&callback) unless @client.nil?
end

.on_error(&callback) ⇒ Object

Set the default on_error callback.

Parameters:

  • &callback (Block)

    called when an error has been detected.



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# File 'lib/nats/client.rb', line 310

def on_error(&callback)
  @err_cb, @err_cb_overridden = callback, true
end

.on_reconnect(&callback) ⇒ Object

Set the default on_reconnect callback.

Parameters:

  • &callback (Block)

    called when a reconnect attempt is made.



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# File 'lib/nats/client.rb', line 316

def on_reconnect(&callback)
  @reconnect_cb = callback
  @client.on_reconnect(&callback) unless @client.nil?
end

.optionsHash

Returns Options

Returns:

  • (Hash)

    Options



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# File 'lib/nats/client.rb', line 297

def options
  return {} unless client
  client.options
end

.pending_data_size(*args) ⇒ Object

Return bytes outstanding for the default client connection.

See Also:



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# File 'lib/nats/client.rb', line 379

def pending_data_size(*args)
  (@client ||= connect).pending_data_size(*args)
end

.publish(*args, &blk) ⇒ Object

Publish a message using the default client connection.

See Also:



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# File 'lib/nats/client.rb', line 337

def publish(*args, &blk)
  (@client ||= connect).publish(*args, &blk)
end

.reconnecting?Boolean

Returns Reconnecting state

Returns:

  • (Boolean)

    Reconnecting state



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# File 'lib/nats/client.rb', line 285

def reconnecting?
  return false unless client
  client.reconnecting?
end

.request(*args, &blk) ⇒ Object

Publish a message and wait for a response on the default client connection.

See Also:



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# File 'lib/nats/client.rb', line 361

def request(*args, &blk)
  (@client ||= connect).request(*args, &blk)
end

.server_infoHash

Returns Server information

Returns:

  • (Hash)

    Server information



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# File 'lib/nats/client.rb', line 303

def server_info
  return nil unless client
  client.server_info
end

.server_running?(uri) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 391

def server_running?(uri) # :nodoc:
  require 'socket'
  s = TCPSocket.new(uri.host, uri.port)
  s.close
  return true
rescue
  return false
end

.start(*args, &blk) ⇒ Object

Create a default client connection to the server.

See Also:

  • connect


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# File 'lib/nats/client.rb', line 233

def start(*args, &blk)
  @reactor_was_running = EM.reactor_running?
  unless (@reactor_was_running || blk)
    raise(Error, "EM needs to be running when NATS.start is called without a run block")
  end
  # Setup optimized select versions
  if EM.epoll?
    EM.epoll
  elsif EM.kqueue?
    EM.kqueue
  elsif EM.library_type == :java
    # No warning needed, we're using Java NIO
  else
    Kernel.warn('Neither epoll nor kqueue are supported, performance may be impacted')
  end
  EM.run { @client = connect(*args, &blk) }
end

.stop(&blk) ⇒ Object

Close the default client connection and optionally call the associated block.

Parameters:

  • &blk (Block)

    called when the connection is closed.



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# File 'lib/nats/client.rb', line 253

def stop(&blk)
  client.close if (client and (client.connected? || client.reconnecting?))
  blk.call if blk
  @err_cb = nil
  @close_cb = nil
  @reconnect_cb = nil
  @disconnect_cb = nil
end

.subscribe(*args, &blk) ⇒ Object

Subscribe using the default client connection.

See Also:



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# File 'lib/nats/client.rb', line 343

def subscribe(*args, &blk)
  (@client ||= connect).subscribe(*args, &blk)
end

.timeout(*args, &blk) ⇒ Object

Set a timeout for receiving messages for the subscription.

See Also:



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# File 'lib/nats/client.rb', line 355

def timeout(*args, &blk)
  (@client ||= connect).timeout(*args, &blk)
end

.unsubscribe(*args) ⇒ Object

Cancel a subscription on the default client connection.

See Also:



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# File 'lib/nats/client.rb', line 349

def unsubscribe(*args)
  (@client ||= connect).unsubscribe(*args)
end

.wait_for_server(uri, max_wait = 5) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 383

def wait_for_server(uri, max_wait = 5) # :nodoc:
  start = Time.now
  while (Time.now - start < max_wait) # Wait max_wait seconds max
    break if server_running?(uri)
    sleep(0.1)
  end
end

Instance Method Details

#attempt_reconnectObject

:nodoc:



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# File 'lib/nats/client.rb', line 1167

def attempt_reconnect #:nodoc:
  @reconnect_timer = nil
  current = server_pool.first

  # Snapshot time when trying to reconnect to server
  # in order to back off for subsequent attempts.
  current[:last_reconnect_attempt] = MonotonicTime.now
  current[:reconnect_attempts] ||= 0
  current[:reconnect_attempts] += 1

  send_connect_command
  begin
    EM.reconnect(@uri.host, @uri.port, self)
  rescue
    current[:error_received] = true
    @uri = nil
    @connected = false
  end
end

#auth_connection?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 772

def auth_connection?
  !@uri.user.nil? || @options[:token]
end

#bind_primaryObject

:nodoc:



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# File 'lib/nats/client.rb', line 1225

def bind_primary #:nodoc:
  first = server_pool.first
  @uri = first[:uri]
  @uri.user = options[:user] if options[:user]
  @uri.password = options[:pass] if options[:pass]
  first
end

#can_reuse_server?(server) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 1161

def can_reuse_server?(server) #:nodoc:
  # If we will retry a number of times to reconnect to a server
  # unless we got an error from it already.
  reconnecting? && server[:reconnect_attempts] <= @options[:max_reconnect_attempts] && !server[:error_received]
end

#cancel_ping_timerObject



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# File 'lib/nats/client.rb', line 997

def cancel_ping_timer
  if @ping_timer
    EM.cancel_timer(@ping_timer)
    @ping_timer = nil
  end
end

#cancel_reconnect_timerObject



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# File 'lib/nats/client.rb', line 1130

def cancel_reconnect_timer
  if @reconnect_timer
    EM.cancel_timer(@reconnect_timer)
    @reconnect_timer = nil
  end
end

#client_using_secure_connection?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 977

def client_using_secure_connection?
  @tls || @ssl
end

#closeObject

Close the connection to the server.



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# File 'lib/nats/client.rb', line 755

def close
  @closing = true
  cancel_ping_timer
  cancel_reconnect_timer
  close_connection_after_writing if connected?
  process_disconnect if reconnecting?
end

#connect_commandObject

:nodoc:



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# File 'lib/nats/client.rb', line 776

def connect_command #:nodoc:
  cs = {
    :verbose => @options[:verbose],
    :pedantic => @options[:pedantic],
    :lang => ::NATS::LANG,
    :version => ::NATS::VERSION,
    :protocol => ::NATS::PROTOCOL_VERSION,
    :echo => !@options[:no_echo]
  }
  case
  when @options[:token]
    cs[:auth_token] = @options[:token]
  when @uri.password.nil?
    cs[:auth_token] = @uri.user
  else
    cs[:user] = @uri.user
    cs[:pass] = @uri.password
  end if auth_connection?

  cs[:name] = @options[:name] if @options[:name]
  cs[:ssl_required] = @ssl if @ssl
  cs[:tls_required] = true if @tls

  "CONNECT #{cs.to_json}#{CR_LF}"
end

#connected_serverURI

Returns Connected server

Returns:

  • (URI)

    Connected server



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# File 'lib/nats/client.rb', line 1215

def connected_server
  connected? ? @uri : nil
end

#connection_completedObject

:nodoc:



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# File 'lib/nats/client.rb', line 1004

def connection_completed #:nodoc:
  @parse_state = AWAITING_CONTROL_LINE

  # Delay sending CONNECT or any other command here until we are sure
  # that we have a valid established secure connection.
  return if (@ssl or @tls)

  # Mark that we established already TCP connection to the server. In case of TLS,
  # prepare commands which will be dispatched to server and delay flushing until
  # we have processed the INFO line sent by the server and done the handshake.
  @connected = true
  process_connect
end

#disconnect_error_stringObject



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# File 'lib/nats/client.rb', line 1137

def disconnect_error_string
  return "Client disconnected from server on #{@uri}" if @connected
  return "Could not connect to server on #{@uri}"
end

#discovered_serversObject

Retrieves the list of servers which have been discovered via server connect_urls announcements



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# File 'lib/nats/client.rb', line 1221

def discovered_servers
  server_pool.select {|s| s[:discovered] }
end

#drain(&blk) ⇒ Object

Drain gracefully closes the connection.

Parameters:

  • blk (Block)

    called when drain is done and connection is closed.



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# File 'lib/nats/client.rb', line 539

def drain(&blk)
  return if draining? or closing?
  @draining = true

  # Remove interest in all subjects to stop receiving messages.
  @subs.each do |sid, _|
    send_command("UNSUB #{sid} #{CR_LF}")
  end

  # Roundtrip to ensure no more messages are received.
  flush do
    drain_timeout_timer, draining_timer = nil, nil
    drain_timeout_timer = EM.add_timer(options[:drain_timeout]) do
      EM.cancel_timer(draining_timer)

      # Report the timeout via the error callback and just close
      err_cb.call(NATS::ClientError.new("Drain Timeout"))
      @draining = false
      close unless closing?
      blk.call if blk
    end

    # Periodically check for the pending data to be empty.
    draining_timer = EM.add_periodic_timer(0.1) do
      next unless closing? or @buf.nil? or @buf.empty?

      # Subscriptions have been drained already so disallow publishing.
      @drained_subs = true
      next unless pending_data_size == 0
      EM.cancel_timer(draining_timer)
      EM.cancel_timer(drain_timeout_timer)

      # We're done draining and can close now.
      @draining = false
      close unless closing?
      blk.call if blk
    end
  end
end

#flush(&blk) ⇒ Object

Flushes all messages and subscriptions for the connection. All messages and subscriptions have been processed by the server when the optional callback is called.



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# File 'lib/nats/client.rb', line 720

def flush(&blk)
  queue_server_rt(&blk) if blk
end

#flush_pendingObject

:nodoc:



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# File 'lib/nats/client.rb', line 845

def flush_pending #:nodoc:
  return unless @pending
  send_data(@pending.join)
  @pending, @pending_size = nil, 0
end

#had_error?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 1122

def had_error?
  server_pool.first && server_pool.first[:error_received]
end

#initialize(options) ⇒ Object



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# File 'lib/nats/client.rb', line 453

def initialize(options)
  @options = options
  process_uri_options

  @buf = nil
  @ssid, @subs = 1, {}
  @err_cb = NATS.err_cb
  @close_cb = NATS.close_cb
  @reconnect_cb = NATS.reconnect_cb
  @disconnect_cb = NATS.disconnect_cb
  @reconnect_timer, @needed = nil, nil
  @connected, @closing, @reconnecting, @conn_cb_called = false, false, false, false
  @msgs_received = @msgs_sent = @bytes_received = @bytes_sent = @pings = 0
  @pending_size = 0
  @server_info = { }

  # Mark whether we should be connecting securely, try best effort
  # in being compatible with present ssl support.
  @ssl = false
  @tls = nil
  @tls = options[:tls] if options[:tls]
  @ssl = options[:ssl] if options[:ssl] or @tls

  # New style request/response implementation.
  @resp_sub = nil
  @resp_map = nil
  @resp_sub_prefix = nil
  @nuid = NATS::NUID.new

  # Drain mode
  @draining = false
  @drained_subs = false
  send_connect_command
end

#inspectObject

:nodoc:



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# File 'lib/nats/client.rb', line 1261

def inspect #:nodoc:
  "<nats client v#{NATS::VERSION}>"
end

#multiple_servers_available?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 1118

def multiple_servers_available?
  server_pool && server_pool.size > 1
end

#on_close(&callback) ⇒ Object

Define a callback to be called when client is disconnected from server.

Parameters:

  • &callback (Block)

    called when will reach a state when will no longer be connected.



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# File 'lib/nats/client.rb', line 750

def on_close(&callback)
  @close_cb = callback
end

#on_connect(&callback) ⇒ Object

Define a callback to be called when the client connection has been established.

Parameters:

  • callback (Block)


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# File 'lib/nats/client.rb', line 726

def on_connect(&callback)
  @connect_cb = callback
end

#on_disconnect(&callback) ⇒ Object

Define a callback to be called when client is disconnected from server.

Parameters:

  • &callback (Block)

    called whenever client disconnects from a server.



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# File 'lib/nats/client.rb', line 744

def on_disconnect(&callback)
  @disconnect_cb = callback
end

#on_error(&callback) ⇒ Object

Define a callback to be called when errors occur on the client connection.

Parameters:

  • &callback (Block)

    called when an error has been detected.



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# File 'lib/nats/client.rb', line 732

def on_error(&callback)
  @err_cb, @err_cb_overridden = callback, true
end

#on_msg(subject, sid, reply, msg) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 812

def on_msg(subject, sid, reply, msg) #:nodoc:

  # Accounting - We should account for inbound even if they are not processed.
  @msgs_received += 1
  @bytes_received += msg.bytesize if msg

  return unless sub = @subs[sid]

  # Check for auto_unsubscribe
  sub[:received] += 1
  if sub[:max]
    # Client side support in case server did not receive unsubscribe
    return unsubscribe(sid) if (sub[:received] > sub[:max])
    # cleanup here if we have hit the max..
    @subs.delete(sid) if (sub[:received] == sub[:max])
  end

  if cb = sub[:callback]
    case cb.arity
      when 0 then cb.call
      when 1 then cb.call(msg)
      when 2 then cb.call(msg, reply)
      else cb.call(msg, reply, subject)
    end
  end

  # Check for a timeout, and cancel if received >= expected
  if (sub[:timeout] && sub[:received] >= sub[:expected])
    EM.cancel_timer(sub[:timeout])
    sub[:timeout] = nil
  end
end

#on_reconnect(&callback) ⇒ Object

Define a callback to be called when a reconnect attempt is made.

Parameters:

  • &callback (Block)

    called when a reconnect attempt is made.



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# File 'lib/nats/client.rb', line 738

def on_reconnect(&callback)
  @reconnect_cb = callback
end

#pending_data_sizeObject

Return bytes outstanding waiting to be sent to server.



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# File 'lib/nats/client.rb', line 764

def pending_data_size
  get_outbound_data_size + @pending_size
end

#process_connectObject

:nodoc:



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# File 'lib/nats/client.rb', line 1023

def process_connect #:nodoc:
  # Reset reconnect attempts since TCP connection has been successful at this point.
  current = server_pool.first
  current[:was_connected] = true
  current[:reconnect_attempts] ||= 0
  cancel_reconnect_timer if reconnecting?

  # Whip through any pending SUB commands since we replay
  # all subscriptions already done anyway.
  @pending.delete_if { |sub| sub[0..2] == SUB_OP } if @pending
  @subs.each_pair { |k, v| send_command("SUB #{v[:subject]} #{v[:queue]} #{k}#{CR_LF}") }

  unless user_err_cb? or reconnecting?
    @err_cb = proc { |e| raise e }
  end

  # We have validated the connection at this point so send CONNECT
  # and any other pending commands which we need to the server.
  flush_pending

  if (connect_cb and not @conn_cb_called)
    # We will round trip the server here to make sure all state from any pending commands
    # has been processed before calling the connect callback.
    queue_server_rt do
      connect_cb.call(self)
      @conn_cb_called = true
    end
  end

  # Notify via reconnect callback that we are again plugged again into the system.
  if reconnecting?
    @reconnecting = false
    @reconnect_cb.call(self) unless @reconnect_cb.nil?
  end

  # Initialize ping timer and processing
  @pings_outstanding = 0
  @pongs_received = 0
  @ping_timer = EM.add_periodic_timer(@options[:ping_interval]) do
    send_ping
  end
end

#process_disconnectObject

:nodoc:



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# File 'lib/nats/client.rb', line 1142

def process_disconnect #:nodoc:
  # Mute error callback when user has called NATS.close on purpose.
  if not closing? and @err_cb
    # Always call error callback for compatibility with previous behavior.
    err_cb.call(NATS::ConnectError.new(disconnect_error_string))
  end
  close_cb.call if @close_cb

  true # Chaining
ensure
  cancel_ping_timer
  cancel_reconnect_timer
  if (NATS.client == self)
    NATS.clear_client
    EM.stop if ((connected? || reconnecting?) and closing? and not NATS.reactor_was_running?)
  end
  @connected = @reconnecting = false
end

#process_info(info) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 904

def process_info(info) #:nodoc:
  # Each JSON parser uses a different key/value pair to use symbol keys
  # instead of strings when parsing. Passing all three pairs assures each
  # parser gets what it needs. For the json gem :symbolize_name, for yajl
  # :symbolize_keys, and for oj :symbol_keys.
  @server_info = JSON.parse(info, :symbolize_keys => true, :symbolize_names => true, :symbol_keys => true)

  case
  when (server_using_secure_connection? and client_using_secure_connection?)
    # Allow parameterizing secure connection via EM#start_tls directly if present.
    start_tls(@tls || {})
  when (server_using_secure_connection? and !client_using_secure_connection?)
    # Call unbind since there is a configuration mismatch between client/server
    # anyway and communication cannot happen in this state.
    err_cb.call(NATS::ClientError.new('TLS/SSL required by server'))
    close_connection_after_writing
  when (client_using_secure_connection? and !server_using_secure_connection?)
    err_cb.call(NATS::ClientError.new('TLS/SSL not supported by server'))
    close_connection_after_writing
  else
    # Otherwise, use a regular connection.
  end

  # Check whether there no echo is supported by the server.
  if @options[:no_echo]
    if @server_info[:proto].nil? || @server_info[:proto] < 1
      err_cb.call(NATS::ServerError.new('No echo option not supported by this server'))
      close_connection_after_writing
    end
  end

  # Detect any announced server that we might not be aware of...
  connect_urls = @server_info[:connect_urls]
  if connect_urls
    srvs = []

    connect_urls.each do |url|
      u = URI.parse("nats://#{url}")
      present = server_pool.detect do |srv|
        srv[:uri].host == u.host && srv[:uri].port == u.port
      end

      if not present
        # Let explicit user and pass options set the credentials.
        u.user = options[:user] if options[:user]
        u.password = options[:pass] if options[:pass]

        # Use creds from the current server if not set explicitly.
        if @uri and !@uri.user.nil? and !@uri.user.empty?
          u.user ||= @uri.user
          u.password ||= @uri.password
        end

        srvs << { :uri => u, :reconnect_attempts => 0, :discovered => true }
      end
    end
    srvs.shuffle! unless @options[:dont_randomize_servers]

    # Include in server pool but keep current one as the first one.
    server_pool.push(*srvs)
  end

  if @server_info[:auth_required]
    current = server_pool.first
    current[:auth_required] = true
    # Send pending connect followed by ping/pong to ensure we're authorized.
    queue_server_rt { current[:auth_ok] = true }
    flush_pending
  end

  @server_info
end

#process_pongObject



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# File 'lib/nats/client.rb', line 1078

def process_pong
  @pongs_received += 1
  @pings_outstanding -= 1
end

#process_uri_optionsObject

Parse out URIs which can now be an array of server choices The server pool will contain both explicit and implicit members.



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# File 'lib/nats/client.rb', line 1206

def process_uri_options #:nodoc
  @server_pool = []
  uri = options[:uris] || options[:servers] || options[:uri]
  uri = uri.kind_of?(Array) ? uri : [uri]
  uri.each { |u| server_pool << { :uri => u.is_a?(URI) ? u.dup : URI.parse(u) } }
  bind_primary
end

#publish(subject, msg = EMPTY_MSG, opt_reply = nil, &blk) ⇒ Object

Publish a message to a given subject, with optional reply subject and completion block

Parameters:

  • subject (String)
  • msg (Object, #to_s) (defaults to: EMPTY_MSG)
  • opt_reply (String) (defaults to: nil)
  • blk, (Block)

    closure called when publish has been processed by the server.



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# File 'lib/nats/client.rb', line 493

def publish(subject, msg=EMPTY_MSG, opt_reply=nil, &blk)
  return unless subject and not @drained_subs
  msg = msg.to_s

  # Accounting
  @msgs_sent += 1
  @bytes_sent += msg.bytesize if msg

  send_command("PUB #{subject} #{opt_reply} #{msg.bytesize}#{CR_LF}#{msg}#{CR_LF}")
  queue_server_rt(&blk) if blk
end

#queue_server_rt(&cb) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 806

def queue_server_rt(&cb) #:nodoc:
  return unless cb
  (@pongs ||= []) << cb
  send_command(PING_REQUEST)
end

#receive_data(data) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 851

def receive_data(data) #:nodoc:
  @buf = @buf ? @buf << data : data

  while (@buf)
    case @parse_state
    when AWAITING_CONTROL_LINE
      case @buf
      when MSG
        @buf = $'
        @sub, @sid, @reply, @needed = $1, $2.to_i, $4, $5.to_i
        @parse_state = AWAITING_MSG_PAYLOAD
      when OK # No-op right now
        @buf = $'
      when ERR
        @buf = $'
        current = server_pool.first
        current[:error_received] = true
        if current[:auth_required] && !current[:auth_ok]
          err_cb.call(NATS::AuthError.new($1))
        else
          err_cb.call(NATS::ServerError.new($1))
        end
      when PING
        @pings += 1
        @buf = $'
        send_command(PONG_RESPONSE)
      when PONG
        @buf = $'
        cb = @pongs.shift
        cb.call if cb
      when INFO
        @buf = $'
        process_info($1)
      when UNKNOWN
        @buf = $'
        err_cb.call(NATS::ServerError.new("Unknown protocol: #{$1}"))
      else
        # If we are here we do not have a complete line yet that we understand.
        return
      end
      @buf = nil if (@buf && @buf.empty?)

    when AWAITING_MSG_PAYLOAD
      return unless (@needed && @buf.bytesize >= (@needed + CR_LF_SIZE))
      on_msg(@sub, @sid, @reply, @buf.slice(0, @needed))
      @buf = @buf.slice((@needed + CR_LF_SIZE), @buf.bytesize)
      @sub = @sid = @reply = @needed = nil
      @parse_state = AWAITING_CONTROL_LINE
      @buf = nil if (@buf && @buf.empty?)
    end
  end
end

#request(subject, data = nil, opts = {}, &cb) ⇒ Object

Send a request and have the response delivered to the supplied callback.

Parameters:

  • subject (String)
  • msg (Object)
  • callback (Block)

Returns:

  • (Object)

    sid



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# File 'lib/nats/client.rb', line 611

def request(subject, data=nil, opts={}, &cb)
  return unless subject

  # In case of using async request then fallback to auto unsubscribe
  # based request/response and not break compatibility too much since
  # new request/response style can only be used with fibers.
  if cb
    inbox = "_INBOX.#{@nuid.next}"
    s = subscribe(inbox, opts) { |msg, reply|
      case cb.arity
      when 0 then cb.call
      when 1 then cb.call(msg)
      else cb.call(msg, reply)
      end
    }
    publish(subject, data, inbox)
    return s
  end

  # If this is the first request being made, then need to start
  # the responses mux handler that handles the responses.
  start_resp_mux_sub! unless @resp_sub_prefix

  # Generate unique token for the reply subject.
  token = @nuid.next
  inbox = "#{@resp_sub_prefix}.#{token}"

  # Synchronous request/response requires using a Fiber
  # to be able to await the response.
  f = Fiber.current
  @resp_map[token][:fiber] = f

  # If awaiting more than a single response then use array
  # to include all that could be gathered before the deadline.
  expected = opts[:max] ||= 1
  @resp_map[token][:expected] = expected
  @resp_map[token][:msgs] = [] if expected > 1

  # Announce the request with the inbox using the token.
  publish(subject, data, inbox)

  # If deadline expires, then discard the token and resume fiber
  opts[:timeout] ||= 0.5
  t = EM.add_timer(opts[:timeout]) do
    if expected > 1
      f.resume @resp_map[token][:msgs]
    else
      f.resume
    end

    @resp_map.delete(token)
  end

  # Wait for the response and cancel timeout callback if received.
  if expected > 1
    # Wait to receive all replies that can get before deadline.
    msgs = Fiber.yield
    EM.cancel_timer(t)

    # Slice and throwaway responses that are not needed.
    return msgs.slice(0, expected)
  else
    msg = Fiber.yield
    EM.cancel_timer(t)
    return msg
  end
end

#schedule_primary_and_connectObject

We have failed on an attempt at the primary (first) server, rotate and try again



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# File 'lib/nats/client.rb', line 1234

def schedule_primary_and_connect #:nodoc:
  # Dump the one we were trying if it wasn't connected
  current = server_pool.shift

  # In case there was an error from the server we will take it out from rotation
  # unless we specify infinite reconnects via setting :max_reconnect_attempts to -1
  if current && (options[:max_reconnect_attempts] < 0 || can_reuse_server?(current))
    server_pool << current
  end

  # If we are out of options, go ahead and disconnect then
  # handle closing connection to NATS.
  process_disconnect and return if server_pool.empty?

  # bind new one
  next_server = bind_primary

  # If the next one was connected and we are trying to reconnect
  # set up timer if we tried once already.
  if should_delay_connect?(next_server)
    schedule_reconnect
  else
    attempt_reconnect
    schedule_primary_and_connect if had_error?
  end
end

#schedule_reconnectObject

:nodoc:



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# File 'lib/nats/client.rb', line 1094

def schedule_reconnect #:nodoc:
  @reconnecting = true
  @connected = false
  @reconnect_timer = EM.add_timer(@options[:reconnect_time_wait]) { attempt_reconnect }
end

#send_command(command, priority = false) ⇒ Object

:nodoc:



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# File 'lib/nats/client.rb', line 1187

def send_command(command, priority = false) #:nodoc:
  needs_flush = (connected? && @pending.nil?)

  @pending ||= []
  @pending << command unless priority
  @pending.unshift(command) if priority
  @pending_size += command.bytesize

  EM.next_tick { flush_pending } if needs_flush

  flush_pending if (connected? && @pending_size > MAX_PENDING_SIZE)
  if (@options[:fast_producer_error] && pending_data_size > FAST_PRODUCER_THRESHOLD)
    err_cb.call(NATS::ClientError.new("Fast Producer: #{pending_data_size} bytes outstanding"))
  end
  true
end

#send_connect_commandObject

:nodoc:



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# File 'lib/nats/client.rb', line 802

def send_connect_command #:nodoc:
  send_command(connect_command, true)
end

#send_pingObject

:nodoc:



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# File 'lib/nats/client.rb', line 1066

def send_ping #:nodoc:
  return if @closing
  @pings_outstanding += 1
  if @pings_outstanding > @options[:max_outstanding_pings]
    close_connection
    #close
    return
  end
  queue_server_rt { process_pong }
  flush_pending
end

#server_using_secure_connection?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 981

def server_using_secure_connection?
  @server_info[:ssl_required] || @server_info[:tls_required]
end

#should_delay_connect?(server) ⇒ Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 1083

def should_delay_connect?(server)
  case
  when server[:was_connected]
    server[:reconnect_attempts] >= 0
  when server[:last_reconnect_attempt]
    (MonotonicTime.now - server[:last_reconnect_attempt]) < @options[:reconnect_time_wait]
  else
    false
  end
end

#should_not_reconnect?Boolean

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 1126

def should_not_reconnect?
  !@options[:reconnect]
end

#ssl_handshake_completedObject



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# File 'lib/nats/client.rb', line 1018

def ssl_handshake_completed
  @connected = true
  process_connect
end

#ssl_verify_peer(cert) ⇒ Object



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# File 'lib/nats/client.rb', line 985

def ssl_verify_peer(cert)
  incoming = OpenSSL::X509::Certificate.new(cert)
  store = OpenSSL::X509::Store.new
  store.set_default_paths
  store.add_file @options[:tls][:ca_file]
  result = store.verify(incoming)
  err_cb.call(NATS::ConnectError.new('TLS Verification failed checking issuer based on CA %s' % @options[:tls][:ca_file])) unless result
  result
rescue NATS::ConnectError
  false
end

#start_resp_mux_sub!Object



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# File 'lib/nats/client.rb', line 679

def start_resp_mux_sub!
  @resp_sub_prefix = "_INBOX.#{@nuid.next}"
  @resp_map = Hash.new { |h,k| h[k] = { }}

  # Single subscription that will be handling all the requests
  # using fibers to yield the responses.
  subscribe("#{@resp_sub_prefix}.*") do |msg, reply, subject|
    token = subject.split('.').last

    # Discard the response if requestor not interested already.
    next unless @resp_map.key? token

    # Take fiber that will be passed the response
    f = @resp_map[token][:fiber]
    expected = @resp_map[token][:expected]

    if expected == 1
      f.resume msg
      @resp_map.delete(token)
      next
    end

    if @resp_map[token][:msgs].size < expected
      @resp_map[token][:msgs] << msg

      msgs = @resp_map[token][:msgs]
      if msgs.size >= expected
        f.resume(msgs)
      else
        # Wait to gather more messages or timeout.
        next
      end
    end

    @resp_map.delete(token)
  end
end

#subscribe(subject, opts = {}, &callback) ⇒ Object

Subscribe to a subject with optional wildcards. Messages will be delivered to the supplied callback. Callback can take any number of the supplied arguments as defined by the list: msg, reply, sub. Returns subscription id which can be passed to #unsubscribe.

Parameters:

  • subject, (String)

    optionally with wilcards.

  • opts, (Hash)

    optional options hash, e.g. :queue, :max.

  • callback, (Block)

    called when a message is delivered.

Returns:

  • (Object)

    sid, Subject Identifier



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# File 'lib/nats/client.rb', line 513

def subscribe(subject, opts={}, &callback)
  return unless subject and not draining?
  sid = (@ssid += 1)
  sub = @subs[sid] = { :subject => subject, :callback => callback, :received => 0 }
  sub[:queue] = opts[:queue] if opts[:queue]
  sub[:max] = opts[:max] if opts[:max]
  send_command("SUB #{subject} #{opts[:queue]} #{sid}#{CR_LF}")
  # Setup server support for auto-unsubscribe
  unsubscribe(sid, opts[:max]) if opts[:max]
  sid
end

#subscription_countNumber

Return the active subscription count.

Returns:

  • (Number)


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# File 'lib/nats/client.rb', line 581

def subscription_count
  @subs.size
end

#timeout(sid, timeout, opts = {}, &callback) ⇒ Object

Setup a timeout for receiving messages for the subscription.

Parameters:

  • sid (Object)
  • timeout, (Number)

    float in seconds

  • opts, (Hash)

    options, :auto_unsubscribe(true), :expected(1)



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# File 'lib/nats/client.rb', line 589

def timeout(sid, timeout, opts={}, &callback)
  # Setup a timeout if requested
  return unless sub = @subs[sid]

  auto_unsubscribe, expected = true, 1
  auto_unsubscribe = opts[:auto_unsubscribe] if opts.key?(:auto_unsubscribe)
  expected = opts[:expected] if opts.key?(:expected)

  EM.cancel_timer(sub[:timeout]) if sub[:timeout]

  sub[:timeout] = EM.add_timer(timeout) do
    unsubscribe(sid) if auto_unsubscribe
    callback.call(sid) if callback
  end
  sub[:expected] = expected
end

#unbindObject

:nodoc:



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# File 'lib/nats/client.rb', line 1100

def unbind #:nodoc:
  # Allow notifying from which server we were disconnected,
  # but only when we didn't trigger disconnecting ourselves.
  if @disconnect_cb and connected? and not closing?
    @disconnect_cb.call(NATS::ConnectError.new(disconnect_error_string))
  end

  # If we are closing or shouldn't reconnect, go ahead and disconnect.
  process_disconnect and return if (closing? or should_not_reconnect?)
  @reconnecting = true if connected?
  @connected = false
  @pending = @pongs = nil
  @buf = nil
  cancel_ping_timer

  schedule_primary_and_connect
end

#unsubscribe(sid, opt_max = nil) ⇒ Object

Cancel a subscription.

Parameters:

  • sid (Object)
  • opt_max, (Number)

    optional number of responses to receive before auto-unsubscribing



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# File 'lib/nats/client.rb', line 528

def unsubscribe(sid, opt_max=nil)
  return if draining?
  opt_max_str = " #{opt_max}" unless opt_max.nil?
  send_command("UNSUB #{sid}#{opt_max_str}#{CR_LF}")
  return unless sub = @subs[sid]
  sub[:max] = opt_max
  @subs.delete(sid) unless (sub[:max] && (sub[:received] < sub[:max]))
end

#user_err_cb?Boolean

:nodoc:

Returns:

  • (Boolean)


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# File 'lib/nats/client.rb', line 768

def user_err_cb? # :nodoc:
  err_cb_overridden || NATS.err_cb_overridden
end