Class: STAN::Client

Inherits:
Object
  • Object
show all
Includes:
MonitorMixin
Defined in:
lib/stan/client.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Client

Returns a new instance of Client.



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# File 'lib/stan/client.rb', line 38

def initialize
  super

  # Connection to NATS, either owned or borrowed
  @nats = nil
  @borrowed_nats_connection = false

  # STAN subscriptions map
  @sub_map = {}

  # Publish Ack map (guid => ack)
  @pub_ack_map = {}
  @pending_pub_acks = nil

  # Cluster to which we are connecting
  @cluster_id = nil
  @client_id = nil

  # Connect options
  @options = {}

  # NATS Streaming subjects

  # Inbox subscription for periodical heartbeat messages
  @hb_inbox = nil
  @hb_inbox_sid = nil

  # Subscription for processing received acks from the server
  @ack_subject = nil
  @ack_subject_sid = nil

  # Publish prefix set by stan to which we append our subject on publish.
  @pub_prefix        = nil
  @sub_req_subject   = nil
  @unsub_req_subject = nil
  @close_req_subject = nil
  @sub_close_req_subject = nil

  # For initial connect request to discover subjects used by
  # the streaming server.
  @discover_subject = nil
end

Instance Attribute Details

#client_id ⇒ Object (readonly)

Returns the value of attribute client_id.



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# File 'lib/stan/client.rb', line 36

def client_id
  @client_id
end

#nats ⇒ Object (readonly)

Returns the value of attribute nats.



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# File 'lib/stan/client.rb', line 36

def nats
  @nats
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/stan/client.rb', line 36

def options
  @options
end

#pending_pub_acks ⇒ Object (readonly)

Returns the value of attribute pending_pub_acks.



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# File 'lib/stan/client.rb', line 36

def pending_pub_acks
  @pending_pub_acks
end

#sub_close_req_subject ⇒ Object (readonly)

Returns the value of attribute sub_close_req_subject.



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# File 'lib/stan/client.rb', line 36

def sub_close_req_subject
  @sub_close_req_subject
end

#sub_map ⇒ Object (readonly)

Returns the value of attribute sub_map.



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# File 'lib/stan/client.rb', line 36

def sub_map
  @sub_map
end

#unsub_req_subject ⇒ Object (readonly)

Returns the value of attribute unsub_req_subject.



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# File 'lib/stan/client.rb', line 36

def unsub_req_subject
  @unsub_req_subject
end

Instance Method Details

#ack(msg) ⇒ Object

Ack takes a received message and publishes an ack manually



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# File 'lib/stan/client.rb', line 314

def ack(msg)
  return unless msg.sub
  msg.sub.synchronize do
    ack_proto = STAN::Protocol::Ack.new({
      subject: msg.proto.subject,
      sequence: msg.proto.sequence
    }).to_proto
    nats.publish(msg.sub.ack_inbox, ack_proto)
  end
end

#close ⇒ Object

Close wraps us the session with the NATS Streaming server



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# File 'lib/stan/client.rb', line 281

def close
  req = STAN::Protocol::CloseRequest.new(clientID: @client_id)
  raw = nats.request(@close_req_subject, req.to_proto)

  resp = STAN::Protocol::CloseResponse.decode(raw.data)
  unless resp.error.empty?
    raise Error.new(resp.error)
  end

  # TODO: If connection to nats was borrowed then we should
  # unsubscribe from all topics from STAN.  If not borrowed
  # and we own the connection, then we just close.
  begin
    # Remove all present subscriptions
    @sub_map.each_pair do |_, sub|
      nats.unsubscribe(sub.sid)
    end

    # Finally, remove the core subscriptions for STAN
    nats.unsubscribe(@hb_inbox_sid)
    nats.unsubscribe(@ack_subject_sid)
  rescue => e
    # TODO: Async error handling
  ensure
    if @borrowed_nats_connection
      @nats = nil
    else
      @nats.close
    end
  end
end

#connect(cluster_id, client_id, opts = {}, &blk) ⇒ Object

Plugs into a NATS Streaming cluster, establishing a connection to NATS in case there is not one available to be borrowed.

Raises:



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# File 'lib/stan/client.rb', line 83

def connect(cluster_id, client_id, opts={}, &blk)
  @cluster_id = cluster_id
  @client_id  = client_id
  @options    = opts

  # Defaults
  @options[:connect_timeout] ||= DEFAULT_CONNECT_TIMEOUT
  @options[:max_pub_acks_inflight] ||= DEFAULT_MAX_PUB_ACKS_INFLIGHT

  # Buffered queue for controlling inflight published acks
  @pending_pub_acks = SizedQueue.new(options[:max_pub_acks_inflight])

  # Prepare connect discovery request
  @discover_subject = "#{DEFAULT_DISCOVER_SUBJECT}.#{@cluster_id}".freeze

  # Prepare delivered msgs acks processing subscription
  @ack_subject = "#{DEFAULT_ACKS_SUBJECT}.#{STAN.create_guid}".freeze

  if @nats.nil?
    case options[:nats]
    when Hash
      # Custom NATS options in case borrowed connection not present
      # can be passed to establish a connection and have stan client
      # owning it.
      @nats = NATS::IO::Client.new
      nats.connect(options[:nats])
    when NATS::IO::Client
      @nats = options[:nats]
      @borrowed_nats_connection = true
    else
      # Try to connect with NATS defaults
      @nats = NATS::IO::Client.new
      nats.connect(servers: ["nats://127.0.0.1:4222"])
    end
  end

  # If no connection to NATS present at this point then bail already
  raise ConnectError.new("stan: invalid connection to nats") unless @nats

  # Heartbeat subscription
  @hb_inbox = (STAN.create_inbox).freeze

  # Setup acks and heartbeats processing callbacks
  @hb_inbox_sid    = nats.subscribe(@hb_inbox)    { |raw| process_heartbeats(raw) }
  @ack_subject_sid = nats.subscribe(@ack_subject) { |raw| process_ack(raw) }
  nats.flush

  # Initial connect request to discover subjects to be used
  # for communicating with STAN.
  req = STAN::Protocol::ConnectRequest.new({
    clientID: @client_id,
    heartbeatInbox: @hb_inbox
  })

  # TODO: Check for error and bail if required
  raw = nats.request(@discover_subject, req.to_proto, timeout: options[:connect_timeout])
  resp = STAN::Protocol::ConnectResponse.decode(raw.data)
  @pub_prefix = resp.pubPrefix.freeze
  @sub_req_subject = resp.subRequests.freeze
  @unsub_req_subject = resp.unsubRequests.freeze
  @close_req_subject = resp.closeRequests.freeze
  @sub_close_req_subject = resp.subCloseRequests.freeze

  # If callback given then we send a close request on exit
  # and wrap up session to STAN.
  if blk
    blk.call(self)

    # Close session to the STAN cluster
    close
  end
end

#publish(subject, payload, opts = {}, &blk) ⇒ Object

Publish will publish to the cluster and wait for an ack



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# File 'lib/stan/client.rb', line 157

def publish(subject, payload, opts={}, &blk)
  stan_subject = "#{@pub_prefix}.#{subject}"
  future = nil
  guid = STAN.create_guid

  pe = STAN::Protocol::PubMsg.new({
    clientID: @client_id,
    guid: guid,
    subject: subject,
    data: payload
  })

  # Use buffered queue to control number of outstanding acks
  @pending_pub_acks << :ack

  if blk
    # Asynchronously handled if block given
    synchronize do
      # Map ack to guid
      @pub_ack_map[guid] = proc do |ack|
        # If block is given, handle the result asynchronously
        error = ack.error.empty? ? nil : Error.new(ack.error)
        case blk.arity
        when 0 then blk.call
        when 1 then blk.call(ack.guid)
        when 2 then blk.call(ack.guid, error)
        end

        @pub_ack_map.delete(ack.guid)
      end

      nats.publish(stan_subject, pe.to_proto, @ack_subject)
    end
  else
    # No block means waiting for response before giving back control
    future = new_cond
    opts[:timeout] ||= DEFAULT_ACK_WAIT

    synchronize do
      # Map ack to guid
      ack_response = nil

      # FIXME: Maybe use fiber instead?
      @pub_ack_map[guid] = proc do |ack|
        # Capture the ack response
        ack_response = ack
        future.signal
      end

      # Send publish request and wait for the ack response
      nats.publish(stan_subject, pe.to_proto, @ack_subject)
      start_time = NATS::MonotonicTime.now
      future.wait(opts[:timeout])
      end_time = NATS::MonotonicTime.now
      if (end_time - start_time) > opts[:timeout]
        # Remove ack
        @pub_ack_map.delete(guid)
        raise TimeoutError.new("stan: timeout")
      end

      # Remove ack
      @pub_ack_map.delete(guid)
      return guid
    end
  end
  # TODO: Loop for processing of expired acks
end

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

Create subscription which dispatches messages to callback asynchronously



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# File 'lib/stan/client.rb', line 226

def subscribe(subject, opts={}, &cb)
  sub_options = {}
  sub_options.merge!(opts)
  sub_options[:ack_wait] ||= DEFAULT_ACK_WAIT
  sub_options[:max_inflight] ||= DEFAULT_MAX_INFLIGHT
  sub_options[:stan] = self

  sub = Subscription.new(subject, sub_options, cb)
  sub.extend(MonitorMixin)
  synchronize { @sub_map[sub.inbox] = sub }

  # Hold lock throughout
  sub.synchronize do
    # Listen for actual messages
    sid = nats.subscribe(sub.inbox) { |raw, reply, subject| process_msg(raw, reply, subject) }
    sub.sid = sid
    nats.flush

    # Create the subscription request announcing the inbox on which
    # we have made the NATS subscription for processing messages.
    # First, we normalize customized subscription options before
    # encoding to protobuf.
    sub_opts = normalize_sub_req_params(sub_options)

    # Set STAN subject and NATS inbox where we will be awaiting
    # for the messages to be delivered.
    sub_opts[:subject] = subject
    sub_opts[:inbox] = sub.inbox

    sr = STAN::Protocol::SubscriptionRequest.new(sub_opts)
    reply = nil
    response = nil
    begin
      reply = nats.request(@sub_req_subject, sr.to_proto, timeout: options[:connect_timeout])
      response = STAN::Protocol::SubscriptionResponse.decode(reply.data)
    rescue NATS::IO::Timeout, Google::Protobuf::ParseError => e
      # FIXME: Error handling on unsubscribe
      nats.unsubscribe(sub.sid)
      raise e
    end

    unless response.error.empty?
      # FIXME: Error handling on unsubscribe
      nats.unsubscribe(sub.sid)
      raise Error.new(response.error)
    end

    # Capture ack inbox for the subscription
    sub.ack_inbox = response.ackInbox.freeze

    return sub
  end
end