Class: Parse::Agent::MCPRackApp::ListeningStreamBody Private

Inherits:
Object
  • Object
show all
Defined in:
lib/parse/agent/mcp_rack_app.rb

Overview

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

Rack body for the long-lived GET listening stream that carries notifications/resources/updated to a subscribing client.

On #each it registers a delivery callback with the Parse::Agent::MCPSubscriptions::Manager keyed by the session id, then blocks reading from an internal queue and yields SSE-formatted notification events as they are published by the LiveQuery bridge. A periodic SSE comment heartbeat keeps the connection warm and surfaces a dead socket as a write error so the Rack server invokes #close.

#close detaches the listener and tears down every LiveQuery subscription bound to the session — so a dropped stream leaves no LiveQuery sockets behind. Re-opening the stream requires the client to re-issue its resources/subscribe calls (subscriptions do not survive a listening-stream disconnect in this single-process implementation).

The publish callback runs on a LiveQuery dispatcher / debounce thread and only pushes to the thread-safe queue; all yields happen on the Rack I/O thread driving #each, mirroring SSEBody's threading model.

Constant Summary collapse

DONE =

This constant is part of a private API. You should avoid using this constant if possible, as it may be removed or be changed in the future. 

:__listening_done__

Instance Method Summary collapse

Constructor Details

#initialize(manager, session_id, heartbeat_interval, logger) ⇒ ListeningStreamBody

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of ListeningStreamBody.

Parameters:



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# File 'lib/parse/agent/mcp_rack_app.rb', line 1685

def initialize(manager, session_id, heartbeat_interval, logger)
  @manager            = manager
  @session_id         = session_id
  @heartbeat_interval = heartbeat_interval
  @logger             = logger
  @queue              = Queue.new
  @heartbeat          = nil
  @closed             = false
  @counted            = false
  @close_mutex        = Mutex.new
end

Instance Method Details

#close ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Terminate the stream: stop heartbeats, detach the listener, and tear down the session's LiveQuery subscriptions. Idempotent.



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# File 'lib/parse/agent/mcp_rack_app.rb', line 1725

def close
  @close_mutex.synchronize do
    return if @closed
    @closed = true
  end
  # Balance the #each increment exactly once (close is idempotent via
  # @closed, and only #each sets @counted).
  MCPRackApp.adjust_listening_stream_count(-1) if @counted
  @heartbeat&.kill
  @heartbeat = nil
  begin
    @manager.detach_listener(@session_id)
  rescue StandardError => e
    line = "[Parse::Agent::MCPRackApp::ListeningStreamBody] detach error: #{e.class}: #{e.message}"
    @logger ? @logger.warn(line) : warn(line)
  end
  @queue << DONE rescue nil
end

#each {|String| ... } ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Rack body interface — called once by the Rack server.

Yields:

  • (String) —

    SSE-formatted event / comment strings.



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# File 'lib/parse/agent/mcp_rack_app.rb', line 1699

def each
  queue = @queue
  # Count this stream against the concurrent-listening-stream soft cap.
  # Incrementing here (in #each, not the constructor) means a body the
  # Rack server never iterates — or a client that disconnects before
  # iteration — never inflates the counter; the matching decrement is in
  # #close, which #each's `ensure` always runs.
  MCPRackApp.adjust_listening_stream_count(1)
  @counted = true
  @manager.attach_listener(@session_id) do |notification|
    queue << format_event(notification)
  end
  # Initial comment flushes response headers and confirms the stream.
  yield ": connected\n\n"
  start_heartbeat
  loop do
    msg = @queue.pop
    break if msg == DONE
    yield msg
  end
ensure
  close
end