Hello, We have an app that uses a ScheduledExecutorService to delay some interactions with another web service. The basic use case here is that a user logs in, performs some action that results in a Runnable being sent to the ScheduledExecutorService with a delay so that it’s executed later, and then the user logs out. This all works fine, except where it doesn’t.
One place where it doesn’t work fine is if we want to update the running app and terminate an instance—any app instance might be holding Runnables that are scheduled to execute later, and yet have no active sessions and would thus be candidates for a shutdown via “refuse new sessions”. Until now, we’ve been keeping track of the scheduled Runnables somewhat indirectly (the details don’t matter), and it’s been reasonably successful. However, it occurred to me that I might be able to use gracefulTerminate() to wait until there are no more outstanding Runnables in the queue. In development, this works just fine: using a while loop we check for outstanding scheduled Runnables and then sleep for 5 seconds. When there are none, we call super.gracefulTerminate() and the app shuts down. My questions: 1. I assume that setting "refuse new sessions” on an instance in JavaMonitor will eventually send a SIGTERM to the app which will be caught by the graceful shutdown mechanism. (Hitting the stop button in Eclipse, for example, doesn’t do that and so gracefulTerminate() isn’t called. You have to simulate it by sending SIGTERM to the Java process from a terminal.) That is, will this even work in production? (I can’t imagine the answer here is no, but would be good to know if anyone’s doing/done it.) 2. The Javadocs for gracefulTerminate() talk about "last minute cleanup”, but I assume we can wait an arbitrary amount of time here. We could conceivably have delays of _hours_ on some of the Runnables in the queue—is this going to bother JavaMonitor (or anything else)? (I assume JavaMonitor will continue to honour “refuse new sessions”, for example.) Obviously we will test this out, but if someone is doing anything like this, it would be great to hear about it. Finally, yes, there are probably much better ways to achieve the outcome here (database-backed Quartz Scheduler, for example), but this was the solution that fit into the budget constraints. -- Paul Hoadley http://logicsquad.net/ _______________________________________________ Do not post admin requests to the list. They will be ignored. Webobjects-dev mailing list ([email protected]) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com This email sent to [email protected]
