Threading and the SystemQueue

Ariba makes it easy to avoid threading issues like synchronization and upcoming problems like deadlocks, race conditions, or access violations. The threading model in Ariba is completely serial, parallelism is avoided whenever possible. If you are using Ariba to write a service or application, two simple guidelines apply:

• Code event driven
• Don't block or wait

When you comply with these two points, you will never get into any threading problems!

Overview of Threading in Ariba

Ariba runs one main thread, called the SystemQueue. All events in Ariba originate the SystemQueue, that means that all functionality is triggered by events that are placed into the SystemQueue. As all functionality is triggerd through the SystemQueue, only one thread exists in Ariba and you can be sure that all code always runs in sync. The concept of one main queue exists in several software projects, and in gernal is called ​Event loop:

• MS Windows uses one main thread in GUI applications (also called the main loop) to schedule and execute GUI changes (details on this are available ​here. The WinMain function in Windows applications that are linked against the Windows Subsystem is such an event loop. It uses the Win32 API GetMessage, TranslateMessage, and DispatchMessage to implement serial message processing in Windows.
• OMNeT++ has an event queue that completely handles execution of simulations (called ​cScheduler. If you compile Ariba with simulation support, the SystemQueue gets synchronized with the OMNeT++ event queue for seamless integration.
• The X Windows System uses event queues in XLib and GLib.

SystemQueue Internals

Using the SystemQueue

Using Blocking Code