Spawning Nested ColdFusion Threads With Synchronous Fallbacks

logger-test.cfm

<cfscript>

	// Create our logger.
	logger = new Logger( expandPath( "./log.txt" ) );


	// Now, let's try to log serval message from both the currently
	// executing page as well as from asynchronous threads.

	logger.logMessage( "In parent page 1." );

	thread
		name = "async1"
		action = "run"
		{

		logger.logMessage ( "In thread 1." );

	}

	thread
		name = "async2"
		action = "run"
		{

		logger.logMessage ( "In thread 2." );

	}

	logger.logMessage( "In parent page 2." );

</cfscript>

Logger.cfc

<cfscript>
component
	output = false
	hint = "I log message to the given text file."
	{

	// I initialize the logger to log to the given file.
	public any function init( required string aFilePath ) {

		filepath = aFilePath;

		return( this );

	}


	// ---
	// PUBLIC METHODS.
	// ---


	// I log the given message.
	public void function logMessage( required string newMessage ) {

		// ColdFUsion has a limit in that threads cannot spawn other
		// threads. As such, if we try to run this code asynchronously,
		// it's possible that it will fail, if the calling context is
		// already inside of a thread. As such, we can TRY to call the
		// code asynchronously; and, if it fails due to a nested-thread
		// error (the only possible point of failure), we can fall back
		// to executing the logging synchronously.
		try {

			logMessageAsync( newMessage );

		} catch ( any error ) {

			logMessageSync( "... Asynchronous logging failed." );
			logMessageSync( newMessage );

		}

	}


	// ---
	// PRIVATE METHODS.
	// ---


	// I execute the logging ASYNCHRONOUSLY.
	private void function logMessageAsync( required string newMessage ) {

		thread
			name = "Logger.logMessageAsync.#createUUID()#"
			action = "run"
			newmessage = newMessage
			{

			logMessageSync( newMessage );

		}

	}


	// I execute the logging SYNCHRONOUSLY.
	private void function logMessageSync( required string newMessage ) {

		lock
			name = filepath
			type = "exclusive"
			timeout = 5
			{

			var logFile = fileOpen( filepath, "append", "utf-8" );

			fileWrite( logFile, ( newMessage & chr( 10 ) ) );

			fileClose( logFile );

		} // END: Lock.

	}

}
</cfscript>