Class: Protobuf::Nats::Server

Inherits:
Object
  • Object
show all
Includes:
Logging, Rpc::Server
Defined in:
lib/protobuf/nats/server.rb

Constant Summary collapse

MILLISECOND = 
1000

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options) ⇒ Server

Returns a new instance of Server.



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# File 'lib/protobuf/nats/server.rb', line 17

def initialize(options)
  @options = options
  @processing_requests = true
  @running = true
  @stopped = false

  @nats = @options[:client] || ::Protobuf::Nats::NatsClient.new
  @nats.connect(::Protobuf::Nats.config.connection_options)

  @thread_pool = ::Protobuf::Nats::ThreadPool.new(@options[:threads], :max_queue => max_queue_size)

  @subscriptions = []
  @server = options.fetch(:server, ::Socket.gethostname)
end

Instance Attribute Details

#nats ⇒ Object (readonly)

Returns the value of attribute nats.



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# File 'lib/protobuf/nats/server.rb', line 13

def nats
  @nats
end

#subscriptions ⇒ Object (readonly)

Returns the value of attribute subscriptions.



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# File 'lib/protobuf/nats/server.rb', line 13

def subscriptions
  @subscriptions
end

#thread_pool ⇒ Object (readonly)

Returns the value of attribute thread_pool.



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# File 'lib/protobuf/nats/server.rb', line 13

def thread_pool
  @thread_pool
end

Instance Method Details

#detect_and_handle_a_pause ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 167

def detect_and_handle_a_pause
  case
  # If we are taking requests and detect a pause file, then unsubscribe.
  when @processing_requests && paused?
    @processing_requests = false
    logger.warn("Pausing server!")
    unsubscribe

  # If we were paused and the pause file is no longer present, then subscribe again.
  when !@processing_requests && !paused?
    logger.warn("Resuming server: resubscribing to all services and restarting slow start!")
    @processing_requests = true
    subscribe
  end
end

#do_not_subscribe_to_includes?(subscription_key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 91

def do_not_subscribe_to_includes?(subscription_key)
  return false unless ::Protobuf::Nats.config.server_subscription_key_do_not_subscribe_to_when_includes_any_of.respond_to?(:any?)
  return false if ::Protobuf::Nats.config.server_subscription_key_do_not_subscribe_to_when_includes_any_of.empty?

  ::Protobuf::Nats.config.server_subscription_key_do_not_subscribe_to_when_includes_any_of.any? do |key|
    subscription_key.include?(key)
  end
end

#enqueue_request(request_data, reply_id) ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 54

def enqueue_request(request_data, reply_id)
  ::ActiveSupport::Notifications.instrument "server.message_received.protobuf-nats"

  enqueued_at = ::Time.now
  was_enqueued = thread_pool.push do
    begin
      # Instrument the thread pool time-to-execute duration.
      processed_at = ::Time.now
      ::ActiveSupport::Notifications.instrument("server.thread_pool_execution_delay.protobuf-nats",
                                                (processed_at - enqueued_at) * MILLISECOND)

      # Process request.
      response_data = handle_request(request_data, 'server' => @server)
      # Publish response.
      nats.publish(reply_id, response_data)
    rescue => error
      ::Protobuf::Nats.notify_error_callbacks(error)
    ensure
      # Instrument the request duration.
      completed_at = ::Time.now
      ::ActiveSupport::Notifications.instrument("server.request_duration.protobuf-nats",
                                                (completed_at - enqueued_at) * MILLISECOND)
    end
  end

  # Publish an ACK to signal the server has picked up the work.
  if was_enqueued
    nats.publish(reply_id, ::Protobuf::Nats::Messages::ACK)
  else
    ::ActiveSupport::Notifications.instrument "server.message_dropped.protobuf-nats"

    nats.publish(reply_id, ::Protobuf::Nats::Messages::NACK)
  end

  was_enqueued
end

#finish_slow_start ⇒ Object

Slow start subscriptions by adding X rounds of subz every Y seconds, where X is subscriptions_per_rpc_endpoint and Y is slow_start_delay.



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# File 'lib/protobuf/nats/server.rb', line 150

def finish_slow_start
  logger.info "Slow start has started..."
  completed = 1

  # We have (X - 1) here because we always subscribe at least once.
  (subscriptions_per_rpc_endpoint - 1).times do
    next unless @running
    next if paused?
    completed += 1
    sleep slow_start_delay
    subscribe_to_services_once
    logger.info "Slow start adding another round of subscriptions (#{completed}/#{subscriptions_per_rpc_endpoint})..."
  end

  logger.info "Slow start finished."
end

#instrument_thread_pool_sizes ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 32

def instrument_thread_pool_sizes
  ::ActiveSupport::Notifications.instrument("server.thread_pool_enqueued_size.protobuf-nats", thread_pool.enqueued_size)
  ::ActiveSupport::Notifications.instrument("server.thread_pool_max_size.protobuf-nats", thread_pool.max_size)
  ::ActiveSupport::Notifications.instrument("server.thread_pool_running_size.protobuf-nats", thread_pool.size)
end

#max_queue_size ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 38

def max_queue_size
  ::ENV.fetch("PB_NATS_SERVER_MAX_QUEUE_SIZE", @options[:threads]).to_i
end

#only_subscribe_to_includes?(subscription_key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 100

def only_subscribe_to_includes?(subscription_key)
  return true unless ::Protobuf::Nats.config.server_subscription_key_only_subscribe_to_when_includes_any_of.respond_to?(:any?)
  return true if ::Protobuf::Nats.config.server_subscription_key_only_subscribe_to_when_includes_any_of.empty?

  ::Protobuf::Nats.config.server_subscription_key_only_subscribe_to_when_includes_any_of.any? do |key|
    subscription_key.include?(key)
  end
end

#pause_file_path ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 109

def pause_file_path
  ::ENV.fetch("PB_NATS_SERVER_PAUSE_FILE_PATH", nil)
end

#paused? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 183

def paused?
  !pause_file_path.nil? && ::File.exist?(pause_file_path)
end

#print_subscription_keys ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 113

def print_subscription_keys
  logger.info "Creating subscriptions:"

  with_each_subscription_key do |subscription_key|
    logger.info "  - #{subscription_key}"
  end
end

#run ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 187

def run
  nats.on_reconnect do
    logger.warn "Server NATS connection was reconnected"
  end

  nats.on_disconnect do
    logger.warn "Server NATS connection was disconnected"
  end

  nats.on_error do |error|
    ::Protobuf::Nats.notify_error_callbacks(error)
  end

  nats.on_close do
    logger.warn "Server NATS connection was closed"
  end

  print_subscription_keys
  if paused?
    yield if block_given?
  else
    subscribe { yield if block_given? }
  end

  loop do
    break unless @running
    detect_and_handle_a_pause
    instrument_thread_pool_sizes
    sleep 1
  end

  unsubscribe

  logger.info "Waiting up to 60 seconds for the thread pool to finish shutting down..."
  thread_pool.shutdown
  thread_pool.wait_for_termination(60)
ensure
  @stopped = true
end

#running? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 227

def running?
  @stopped
end

#service_klasses ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 50

def service_klasses
  ::Protobuf::Rpc::Service.implemented_services.map(&:safe_constantize)
end

#slow_start_delay ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 42

def slow_start_delay
  @slow_start_delay ||= ::ENV.fetch("PB_NATS_SERVER_SLOW_START_DELAY", 10).to_i
end

#stop ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 231

def stop
  @running = false
end

#subscribe ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 235

def subscribe
  subscribe_to_services_once
  yield if block_given?
  finish_slow_start
end

#subscribe_to_services_once ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 121

def subscribe_to_services_once
  with_each_subscription_key do |subscription_key_and_queue|
    subscriptions << nats.subscribe(subscription_key_and_queue, :queue => subscription_key_and_queue) do |request_data, reply_id, _subject|
      unless enqueue_request(request_data, reply_id)
        logger.error { "Thread pool is full! Dropping message for: #{subscription_key_and_queue}" }
      end
    end
  end
end

#subscriptions_per_rpc_endpoint ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 46

def subscriptions_per_rpc_endpoint
  @subscriptions_per_rpc_endpoint ||= ::ENV.fetch("PB_NATS_SERVER_SUBSCRIPTIONS_PER_RPC_ENDPOINT", 10).to_i
end

#unsubscribe ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 241

def unsubscribe
  logger.info "Unsubscribing from rpc routes..."
  subscriptions.each do |subscription_id|
    nats.unsubscribe(subscription_id)
  end
end

#with_each_subscription_key ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 131

def with_each_subscription_key
  fail ::ArgumentError unless block_given?

  service_klasses.each do |service_klass|
    service_klass.rpcs.each do |service_method, _|
      # Skip services that are not implemented.
      next unless service_klass.method_defined?(service_method)
      subscription_key = ::Protobuf::Nats.subscription_key(service_klass, service_method)
      next if do_not_subscribe_to_includes?(subscription_key)
      next unless only_subscribe_to_includes?(subscription_key)

      yield subscription_key
    end
  end
end