4e78ef2249
Currently ThreadGroup.stop() would stop both timers and threads immediately. However, heat-engine should stop timers before threads finished for the purpose of graceful shutdown. The graceful shutdown for Heat is "do process exit after stack processing finished". Heat implemented the stack processing as threads. We should wait its finishing for graceful shutdown's purpose. On the one hand, Heat is using timers. The timers have the function of make another job threads. It means, we should stop timers before waiting threads for preventing another thread occur by timers. From the above, the appropriate order of Heat's graceful shutdown is: * stop timers for preventing new thread occur * wait for all threads to be finished * process exit However, currently ThreadGroup class doesn't have the function of graceful stop. So I propose the function of graceful stop. Change-Id: Id575674af95ae7ad88c00a2ac5d629ab0d0a9b46 Closes-bug: #1304244