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 20

def initialize(options)
  @options = options
  @processing_requests = true
  @running = true
  @stopped = false
  @pause_mutex = ::Mutex.new

  @nats = @options[:client] || ::Protobuf::Nats::NatsClient.new

  # Register lifecycle callbacks BEFORE connecting so a disconnect or
  # error during the initial handshake is still observed (mirrors
  # Protobuf::Nats.start_client_nats_connection on the client side).
  @nats.on_disconnect do
    logger.warn "Server NATS connection was disconnected"
  end

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

  @nats.on_error do |error|
    # Runs on nats-pure's read/flush thread -- offload so a slow callback
    # can't stall the server's intake.
    ::Protobuf::Nats.notify_error_callbacks_async(error)
  end

  @nats.on_close do
    handle_connection_closed
  end

  @nats.connect(::Protobuf::Nats.config.connection_options)

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

  @subscription_manager = ::Protobuf::Nats::SuperSubscriptionManager.new(@nats) do |request_data, reply_id, subject|
    # Opt-in intake shedding; rationale on #stale_request_ms.
    next if stale_request?(reply_id)

    unless enqueue_request(request_data, reply_id)
      logger.error { "Thread pool is full! Dropping message for subject: #{subject}" }
    end
  end
  @server = options.fetch(:server, ::Socket.gethostname)

  # In-flight handler tracking for observability. Long-running handlers are
  # allowed (and never aborted); we only measure/report. id => monotonic
  # start time; @overdue_flagged dedupes the per-handler overdue event.
  @inflight = ::Concurrent::Map.new
  @overdue_flagged = ::Concurrent::Map.new
  @request_seq = ::Concurrent::AtomicFixnum.new(0)
end

Instance Attribute Details

#nats ⇒ Object (readonly)

Returns the value of attribute nats.



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# File 'lib/protobuf/nats/server.rb', line 16

def nats
  @nats
end

#subscription_manager ⇒ Object (readonly)

Returns the value of attribute subscription_manager.



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# File 'lib/protobuf/nats/server.rb', line 16

def subscription_manager
  @subscription_manager
end

#thread_pool ⇒ Object (readonly)

Returns the value of attribute thread_pool.



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# File 'lib/protobuf/nats/server.rb', line 16

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 394

def detect_and_handle_a_pause
  @pause_mutex.synchronize do
    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
end

#do_not_subscribe_to_includes?(subscription_key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 314

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 213

def enqueue_request(request_data, reply_id)
  ::Protobuf::Nats.instrument "server.message_received"

  enqueued_at = monotonic
  request_id = @request_seq.increment
  was_enqueued = thread_pool.push do
    # nil response_data is the "handler failed, don't publish a success
    # response" sentinel (a successful encode is always a non-nil String,
    # even when empty).
    response_data = nil
    begin
      # Instrument the thread pool time-to-execute duration.
      processed_at = monotonic
      ::Protobuf::Nats.instrument("server.thread_pool_execution_delay", (processed_at - enqueued_at) * MILLISECOND)

      # Track this handler as in-flight (long handlers are allowed; this is
      # only for observability -- we never abort it unless overdue-reclaim
      # is explicitly enabled). Store the worker thread so reclaim can
      # target it; the start time drives age/overdue accounting.
      @inflight[request_id] = [processed_at, ::Thread.current]

      # Process request. Only the handler is wrapped here so a transport
      # failure on the success-response publish (below) cannot fall into
      # this rescue and emit a *second* (error) publish for a request whose
      # handler actually succeeded.
      begin
        response_data = handle_request(request_data, 'server' => @server)
      rescue => error
        response_data = nil # ensure the success-publish below is skipped
        logger.debug { "rescued error => #{error}" }  if logger.debug?
        # Logs the real error server-side (via the default log_error
        # callback) so it isn't lost; the client gets only a generic message.
        ::Protobuf::Nats.notify_error_callbacks(error)

        # The client has already received our ACK and is now blocked waiting
        # for the response message. If we don't send one it will hang until
        # response_timeout (60s by default). Publish an encoded RPC error so
        # the client fails fast instead. Use a generic message rather than
        # error.message so internal handler details aren't leaked over the
        # wire. (If the failure was the connection itself, this publish will
        # also fail and is swallowed below.)
        begin
          error_response = ::Protobuf::Rpc::PbError.new("Internal server error")
          nats.publish(reply_id, error_response.encode)
        rescue => publish_error
          logger.error "Failed to publish error response for #{reply_id}: #{publish_error.message}"
        end
      end

      # Publish the successful response. Kept outside the handler rescue so a
      # publish failure here is logged rather than triggering a duplicate
      # (error) response for a request that already succeeded.
      if response_data
        logger.debug { "Publishing response to #{reply_id}" } if logger.debug?
        begin
          nats.publish(reply_id, response_data)
        rescue => publish_error
          logger.error "Failed to publish response for #{reply_id}: #{publish_error.message}"
          ::Protobuf::Nats.notify_error_callbacks(publish_error)
        end
      end
    ensure
      @inflight.delete(request_id)
      @overdue_flagged.delete(request_id)

      # Instrument the request duration.
      completed_at = monotonic
      ::Protobuf::Nats.instrument("server.request_duration", (completed_at - enqueued_at) * MILLISECOND)

      # Informational slow-handler marker (opt-in; default off).
      if processed_at && slow_handler_threshold_ms.positive?
        handler_ms = (completed_at - processed_at) * MILLISECOND
        if handler_ms >= slow_handler_threshold_ms
          logger.warn "Slow handler for #{reply_id}: #{handler_ms.round}ms"
          ::Protobuf::Nats.instrument("server.slow_handler", handler_ms)
        end
      end
    end
  end

  # Publish an ACK to signal the server has picked up the work.
  begin
    if was_enqueued
      logger.debug { "[reply_id=#{reply_id}] Sending ACK" } if logger.debug?
      nats.publish(reply_id, ::Protobuf::Nats::Messages::ACK)
    else # Drop message if the thread pool is full
      ::Protobuf::Nats.instrument "server.thread_pool_saturated"
      ::Protobuf::Nats.instrument "server.message_dropped"
      logger.debug { "[reply_id=#{reply_id}] Sending NACK" } if logger.debug?

      # Let the client know we are not processing the message.
      nats.publish(reply_id, ::Protobuf::Nats::Messages::NACK)
    end
  rescue => e
    logger.error "Failed to send ACK/NACK for #{reply_id}: #{e.message}"
    ::Protobuf::Nats.notify_error_callbacks(e)
  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 369

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
    unless @running
      logger.info "Slow start interrupted (server stopping) after #{completed}/#{subscriptions_per_rpc_endpoint} rounds"
      return
    end

    if paused?
      logger.info "Slow start interrupted (server paused) after #{completed}/#{subscriptions_per_rpc_endpoint} rounds"
      return
    end

    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 successfully (#{completed}/#{subscriptions_per_rpc_endpoint} rounds completed)."
end

#handle_connection_closed ⇒ Object

nats-pure fires on_close when the connection is terminally closed: either we called close (normal shutdown, @running already false) or the reconnect loop exhausted max_reconnect_attempts on every server in the pool. In the latter case the server would otherwise keep running forever with a dead connection -- subscribed to nothing, receiving nothing -- indistinguishable from healthy-but-idle. Stop the run loop instead so the process exits and the supervisor (systemd/k8s/foreman) restarts it with a fresh connection. Deployments that prefer in-process retries forever can set max_reconnect_attempts: -1, in which case nats-pure never fires this for a mere outage.



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# File 'lib/protobuf/nats/server.rb', line 426

def handle_connection_closed
  return unless @running
  logger.error "Server NATS connection was closed unexpectedly (reconnect attempts exhausted); stopping server so a supervisor can restart it"
  ::Protobuf::Nats.instrument "server.connection_closed"
  stop
end

#handler_count ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 76

def handler_count
  subscription_manager.handler_count
end

#handler_overdue_ms ⇒ Object

A handler still running past this is "overdue": the client has already given up (its response_timeout), so the work is orphaned and holding a pool slot for nothing. Defaults above the client's 60s response_timeout so legitimate ≤60s operations are never flagged.



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

def handler_overdue_ms
  @handler_overdue_ms ||= ::Protobuf::Nats.env_int("PB_NATS_SERVER_HANDLER_OVERDUE_MS", 65_000)
end

#instrument_inflight_handlers ⇒ Object

Periodic in-flight handler health. Long handlers are normal, so inflight_oldest_age_ms can legitimately approach the client's response_timeout; only overdue_handler_count (work the client has already abandoned) signals a problem.



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# File 'lib/protobuf/nats/server.rb', line 147

def instrument_inflight_handlers
  now = monotonic
  overdue_ms = handler_overdue_ms
  count = 0
  oldest_age_ms = 0.0
  overdue = 0

  @inflight.each_pair do |id, entry|
    started_at, handler_thread = entry
    count += 1
    age_ms = (now - started_at) * MILLISECOND
    oldest_age_ms = age_ms if age_ms > oldest_age_ms
    next unless overdue_ms.positive? && age_ms >= overdue_ms

    overdue += 1

    # Optionally reclaim the slot by aborting the orphaned handler (opt-in;
    # see #reclaim_overdue_handlers?). Done before the dedupe below so the
    # reclaim is attempted even after the overdue event was already emitted.
    # The @inflight re-check narrows the window in which the raise could
    # land on a worker that already finished this request and moved on to
    # another (the ThreadPool worker also swallows a raise that lands
    # between tasks).
    if reclaim_overdue_handlers? && handler_thread&.alive? && @inflight[id].equal?(entry)
      logger.warn "Reclaiming overdue handler (age=#{age_ms.round}ms, client already gave up) to free its pool slot"
      handler_thread.raise(::Protobuf::Nats::Errors::HandlerOverdue, "handler exceeded #{overdue_ms}ms; reclaimed")
      ::Protobuf::Nats.instrument("server.handler_reclaimed", age_ms)
    end

    # Emit the per-handler overdue event once (the client has already
    # given up; this handler's result is orphaned).
    next if @overdue_flagged[id]
    @overdue_flagged[id] = true
    logger.warn "Handler exceeded #{overdue_ms}ms (client already gave up); in-flight age=#{age_ms.round}ms"
    ::Protobuf::Nats.instrument("server.handler_overdue", age_ms)
  end

  ::Protobuf::Nats.instrument("server.pending_intake_queue_size", subscription_manager.pending_queue_size)
  ::Protobuf::Nats.instrument("server.inflight_count", count)
  ::Protobuf::Nats.instrument("server.inflight_oldest_age_ms", oldest_age_ms)
  ::Protobuf::Nats.instrument("server.overdue_handler_count", overdue)
end

#instrument_thread_pool_sizes ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 137

def instrument_thread_pool_sizes
  ::Protobuf::Nats.instrument("server.thread_pool_enqueued_size", thread_pool.enqueued_size)
  ::Protobuf::Nats.instrument("server.thread_pool_max_size", thread_pool.max_size)
  ::Protobuf::Nats.instrument("server.thread_pool_running_size", thread_pool.size)
end

#max_queue_size ⇒ Object

Defaults to #threads (not the raw option) so a server built with no :threads option gets a queue matching its 10 default workers instead of nil.to_i == 0.



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# File 'lib/protobuf/nats/server.rb', line 193

def max_queue_size
  ::Protobuf::Nats.env_int("PB_NATS_SERVER_MAX_QUEUE_SIZE", threads)
end

#monotonic ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 72

def monotonic
  ::Protobuf::Nats.monotonic_time
end

#only_subscribe_to_includes?(subscription_key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 323

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 332

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 412

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 336

def print_subscription_keys
  logger.info "Creating subscriptions:"

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

#reclaim_overdue_handlers? ⇒ Boolean

Whether to actively reclaim (abort) an overdue handler's pool slot. OFF by default: the documented contract is that handlers are never aborted, since killing a thread mid-handler can corrupt state. Enable only when you would rather shed orphaned work (whose client already gave up) than let it pin a pool slot -- e.g. when overdue handlers are saturating the pool and the server is NACKing healthy traffic. Reclaim raises Errors::HandlerOverdue into the worker, which the handler rescue turns into an RPC error response.

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 124

def reclaim_overdue_handlers?
  # Memoize the raw string (never falsey, so ||= is safe) and derive the
  # boolean per call -- avoids the nil-guard dance for a false-able memo.
  @reclaim_overdue_handlers ||= ::ENV.fetch("PB_NATS_SERVER_RECLAIM_OVERDUE_HANDLERS", "false")
  @reclaim_overdue_handlers == "true"
end

#run ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 433

def run
  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
    instrument_inflight_handlers
    thread_pool.replenish # respawn workers killed by non-StandardError
    sleep 1
  end

  unsubscribe

  logger.info "Shutting down subscription manager..."
  begin
    Timeout.timeout(10) do
      subscription_manager.shutdown(5)
    end
  rescue Timeout::Error
    logger.error "Subscription manager shutdown timed out!"
  rescue => e
    logger.error "Error during subscription manager shutdown: #{e.message}"
  end

  # Give in-flight handlers time to finish. Long operations are allowed
  # (up to ~the client's response_timeout), so the drain timeout tracks
  # handler_overdue_ms rather than a fixed 60s -- otherwise a legitimate
  # ~60s handler would be killed and its client left waiting.
  drain_timeout = shutdown_drain_timeout
  logger.info "Waiting up to #{drain_timeout.round}s for the thread pool to finish shutting down..."
  thread_pool.shutdown
  unless thread_pool.wait_for_termination(drain_timeout)
    abandoned = @inflight.size
    logger.warn "Thread pool did not shut down cleanly within #{drain_timeout.round}s! Abandoned #{abandoned} in-flight handler(s)."
    ::Protobuf::Nats.instrument "server.thread_pool_shutdown_timeout"
    ::Protobuf::Nats.instrument "server.shutdown_abandoned_handlers", abandoned
  end
ensure
  @stopped = true

  begin
    logger.info "Closing NATS connection..."
    @nats.close if @nats
  rescue => e
    logger.warn "Failed to close NATS connection: #{e.message}"
  end
end

#running? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 487

def running?
  !@stopped
end

#service_klasses ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 209

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

#shutdown_drain_timeout ⇒ Object

How long to let in-flight handlers finish on shutdown. Tracks the overdue window (plus grace) so a legitimate long handler isn't killed mid-flight.



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# File 'lib/protobuf/nats/server.rb', line 133

def shutdown_drain_timeout
  @shutdown_drain_timeout ||= ::Protobuf::Nats.env_float("PB_NATS_SERVER_SHUTDOWN_DRAIN_TIMEOUT", (handler_overdue_ms / 1000.0) + 5)
end

#slow_handler_threshold_ms ⇒ Object

Informational SLA marker for slow handlers. Default 0 (off) so normal long-running operations are not flagged.



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# File 'lib/protobuf/nats/server.rb', line 82

def slow_handler_threshold_ms
  @slow_handler_threshold_ms ||= ::Protobuf::Nats.env_int("PB_NATS_SERVER_SLOW_HANDLER_THRESHOLD_MS", 0)
end

#slow_start_delay ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 197

def slow_start_delay
  @slow_start_delay ||= ::Protobuf::Nats.env_int("PB_NATS_SERVER_SLOW_START_DELAY", 10)
end

#stale_request?(reply_id) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/protobuf/nats/server.rb', line 98

def stale_request?(reply_id)
  return false unless stale_request_ms.positive?

  age_ms = ::Protobuf::Nats::UUIDv7Helper.age_ms(reply_id.to_s[/[^.]*\z/])
  return false if age_ms.nil? || age_ms < stale_request_ms

  logger.debug { "Dropping stale request (age=#{age_ms}ms >= #{stale_request_ms}ms); the client has already retried or timed out" }
  ::Protobuf::Nats.instrument "server.stale_request_dropped", age_ms
  true
end

#stale_request_ms ⇒ Object

Age (ms) beyond which a request is shed at intake instead of processed: a request whose client has already retried or timed out is abandoned work -- executing it only burns a pool slot (and duplicates effects for non-idempotent RPCs). Default 0 (off). The age comes from the UUIDv7 token this gem's client embeds in the reply inbox, which encodes client wall-clock time -- enable only with sane NTP across hosts, and keep the threshold comfortably above the client's ack_timeout (5s default) to absorb skew.



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# File 'lib/protobuf/nats/server.rb', line 94

def stale_request_ms
  @stale_request_ms ||= ::Protobuf::Nats.env_int("PB_NATS_SERVER_STALE_REQUEST_MS", 0)
end

#stop ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 491

def stop
  @running = false
end

#subscribe ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 495

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 344

def subscribe_to_services_once
  with_each_subscription_key do |subscription_key_and_queue|
    subscription_manager.queue_subscribe(subscription_key_and_queue)
  end
end

#subscriptions_per_rpc_endpoint ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 201

def subscriptions_per_rpc_endpoint
  @subscriptions_per_rpc_endpoint ||= ::Protobuf::Nats.env_int("PB_NATS_SERVER_SUBSCRIPTIONS_PER_RPC_ENDPOINT", 10)
end

#threads ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 205

def threads
  @options[:threads] || 10 # Default to 10 if not provided, consistent with original behavior
end

#unsubscribe ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 501

def unsubscribe
  logger.info "Unsubscribing from rpc routes..."
  subscription_manager.unsubscribe_all
end

#with_each_subscription_key ⇒ Object 



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# File 'lib/protobuf/nats/server.rb', line 350

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