Shutting down the application gracefully

Servers and daemons are the programs that run for a long time (typically days or even weeks). These long-running programs usually allocate resources (database connections, network sock) at the start and keep these resources as long as they exist. If such a process is killed and the shutdown is not handled properly, a resource leak could happen. To avoid that behavior, the so-called graceful shutdown should be implemented.

Graceful, in this case, means that the application catches the termination signal, if possible, and tries to clean up and release the allocated resources before it terminates. This recipe will show you how to implement the graceful shutdown.

The recipe, Handling operating system signals describes the catching of OS signals. The same approach will be used for implementing the graceful shutdown. Before the program terminates, it will clean up and carry out some other activities.