Module: MCPClient::ServerSSE::ReconnectMonitor

Includes:
OriginPolicy
Included in:
MCPClient::ServerSSE
Defined in:
lib/mcp_client/server_sse/reconnect_monitor.rb

Overview

Extracted module for back-off, ping, and reconnection logic

Instance Method Summary collapse

Methods included from OriginPolicy

#origin_of, #reject_cross_origin_redirect!, #same_origin?

Instance Method Details

#activity_monitor_loop ⇒ void

This method returns an undefined value.

Main loop for the activity monitor thread



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 40

def activity_monitor_loop
  loop do
    sleep 1

    unless connection_active?
      @logger.debug('Activity monitor exiting: connection no longer active')
      return
    end

    @mutex.synchronize do
      @consecutive_ping_failures ||= 0
      @reconnect_attempts ||= 0
      @max_ping_failures ||= DEFAULT_MAX_PING_FAILURES
      @max_reconnect_attempts ||= DEFAULT_MAX_RECONNECT_ATTEMPTS
    end

    return unless connection_active?

    time_since_activity = Time.now - @last_activity_time

    if @close_after && time_since_activity >= @close_after
      @logger.info("Closing connection due to inactivity (#{time_since_activity.round(1)}s)")
      cleanup
      return
    end

    next unless @ping_interval && time_since_activity >= @ping_interval
    return unless connection_active?

    if @consecutive_ping_failures >= @max_ping_failures
      attempt_reconnection
    else
      attempt_ping
    end
  end
end

#attempt_ping ⇒ void

This method returns an undefined value.

Attempt to ping the server to check if connection is still alive



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 125

def attempt_ping
  unless connection_active?
    @logger.debug('Skipping ping - connection not active')
    return
  end

  time_since = Time.now - @last_activity_time
  @logger.debug("Sending ping after #{time_since.round(1)}s of inactivity")

  begin
    ping
    @mutex.synchronize do
      @last_activity_time = Time.now
      @consecutive_ping_failures = 0
    end
  rescue StandardError => e
    unless connection_active?
      @logger.debug("Ignoring ping failure - connection already closed: #{e.message}")
      return
    end
    handle_ping_failure(e)
  end
end

#attempt_reconnection ⇒ void

This method returns an undefined value.

Attempt to reconnect with exponential backoff



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 80

def attempt_reconnection
  if @reconnect_attempts < @max_reconnect_attempts
    begin
      base_delay = BASE_RECONNECT_DELAY * (2**@reconnect_attempts)
      jitter = rand * JITTER_FACTOR * base_delay
      backoff_delay = [base_delay + jitter, MAX_RECONNECT_DELAY].min

      reconnect_msg = "Attempting to reconnect (attempt #{@reconnect_attempts + 1}/#{@max_reconnect_attempts}) "
      reconnect_msg += "after #{@consecutive_ping_failures} consecutive ping failures. "
      reconnect_msg += "Waiting #{backoff_delay.round(2)}s before reconnect..."
      @logger.warn(reconnect_msg)
      sleep(backoff_delay)

      cleanup

      # Clear any stale auth/connection error from the previous connection
      # so it does not spuriously abort this reconnect via
      # wait_for_connection.
      @mutex.synchronize do
        @auth_error = nil
        @connection_error = nil
      end

      connect
      @logger.info('Successfully reconnected after ping failures')

      @mutex.synchronize do
        @consecutive_ping_failures = 0
        # Reset attempt counter after a successful reconnect
        @reconnect_attempts = 0
        @last_activity_time = Time.now
      end
    rescue StandardError => e
      @logger.error("Failed to reconnect after ping failures: #{e.message}")
      @mutex.synchronize { @reconnect_attempts += 1 }
    end
  else
    @logger.error("Exceeded maximum reconnection attempts (#{@max_reconnect_attempts}). Closing connection.")
    cleanup
  end
end

#connection_active? ⇒ Boolean

Check if the connection is currently active

Returns:

  • (Boolean) —

    true if connection is established and SSE is connected



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 33

def connection_active?
  @mutex.synchronize { @connection_established && @sse_connected }
end

#handle_ping_failure(error) ⇒ void

This method returns an undefined value.

Handle ping failures by incrementing a counter and logging

Parameters:

  • error (StandardError) —

    the error that caused the ping failure



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 153

def handle_ping_failure(error)
  @mutex.synchronize { @consecutive_ping_failures += 1 }
  consecutive_failures = @consecutive_ping_failures

  if consecutive_failures == 1
    @logger.error("Error sending ping: #{error.message}")
  else
    error_msg = error.message.split("\n").first
    @logger.warn("Ping failed (#{consecutive_failures}/#{@max_ping_failures}): #{error_msg}")
  end
end

#handle_sse_auth_error(error) ⇒ void

This method returns an undefined value.

Handle authentication errors from SSE

Parameters:

  • error (StandardError) —

    the authentication error



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 223

def handle_sse_auth_error(error)
  error_message = "Authorization failed: HTTP #{error.response[:status]}"
  @logger.error(error_message)

  @mutex.synchronize do
    @auth_error = error_message
    @connection_established = false
    @connection_cv.broadcast
  end
end

#record_activity ⇒ void

This method returns an undefined value.

Record activity to prevent unnecessary pings



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 167

def record_activity
  @mutex.synchronize { @last_activity_time = Time.now }
end

#reset_connection_state ⇒ void

This method returns an undefined value.

Reset the connection state



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 237

def reset_connection_state
  @mutex.synchronize do
    @connection_established = false
    @connection_cv.broadcast
  end
end

#setup_sse_connection(uri) ⇒ Faraday::Connection

Setup the SSE connection with Faraday

Parameters:

  • uri (URI) —

    the URI to connect to

Returns:

  • (Faraday::Connection) —

    the configured connection



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 202

def setup_sse_connection(uri)
  sse_base = "#{uri.scheme}://#{uri.host}:#{uri.port}"

  @sse_conn ||= Faraday.new(url: sse_base) do |f|
    f.options.open_timeout = 10
    f.options.timeout = nil
    f.request :retry, max: @max_retries, interval: @retry_backoff, backoff_factor: 2
    # Same origin pinning as the RPC connection: the SSE stream carries
    # the configured credential headers too.
    f.response :follow_redirects, limit: 3, callback: method(:reject_cross_origin_redirect!)
    f.adapter Faraday.default_adapter
  end

  @sse_conn.builder.use Faraday::Response::RaiseError
  @sse_conn
end

#start_activity_monitor ⇒ void

This method returns an undefined value.

Start an activity monitor thread to maintain the connection



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 13

def start_activity_monitor
  return if @activity_timer_thread&.alive?

  @mutex.synchronize do
    @last_activity_time = Time.now
    @consecutive_ping_failures = 0
    @max_ping_failures = DEFAULT_MAX_PING_FAILURES
    @reconnect_attempts = 0
    @max_reconnect_attempts = DEFAULT_MAX_RECONNECT_ATTEMPTS
  end

  @activity_timer_thread = Thread.new do
    activity_monitor_loop
  rescue StandardError => e
    @logger.error("Activity monitor error: #{e.message}")
  end
end

#wait_for_connection(timeout:) ⇒ void

This method returns an undefined value.

Wait for the connection to be established

Parameters:

  • timeout (Numeric) —

    timeout in seconds

Raises:



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# File 'lib/mcp_client/server_sse/reconnect_monitor.rb', line 175

def wait_for_connection(timeout:)
  @mutex.synchronize do
    deadline = Time.now + timeout

    until @connection_established
      break if @connection_error

      remaining = [1, deadline - Time.now].min
      break if remaining <= 0 || @connection_cv.wait(remaining) { @connection_established }
    end

    raise MCPClient::Errors::ConnectionError, @auth_error if @auth_error
    raise MCPClient::Errors::ConnectionError, @connection_error if @connection_error

    unless @connection_established
      cleanup
      error_msg = "Failed to connect to MCP server at #{@base_url}"
      error_msg += ': Timed out waiting for SSE connection to be established'
      raise MCPClient::Errors::ConnectionError, error_msg
    end
  end
end