The logger module is included in ScriptBasic though it is not a critical part of it. The command line version itself does not use the functions implemented in this module, though the functions are available for external modules. The Eszter SB Application Engine uses this module to asynchronously log hits and other events to ASCII text log files.
This module can be used to log events. The module implements two type of logs.
Synchronous logs are just the normal plain logging technic writing messages to a log file. This is low performance, because the caller has to wait until the logging is performed and written to a file. On the other hand this is a safe logging.
Asynchronous logging is a fast performance logging method. In this case the caller passes the log item to the logger. The logger puts the item on a queue and sends it to the log file in another thread when disk I/O bandwith permits. This is high performance, because the caller does not need to wait for the log item written to the disk. On the other hand this logging is not safe because the caller can not be sure that the log was written to the disk.
The program using this module should use asynchronous logging for high volume logs and synchronous logging for low volume logging. For example a panic log that reports configuration error has to be written synchronously.
Using this module you can initialize a log specifying the file where to write the log, send logs and you can tell the log to shut down. When shutting down all waiting logs are written to the file and no more log items are accepted. When all logs are written the logging thread terminates.