Hi Nick, Thanks for your feedback. Yes, I'm very interested in seeing this included in the official SDK. What are the steps from here?
See responses to specific questions inserted below. Vince > - Perhaps make PermanentTaskFailure a runtime exception, which would > eliminate the need to declare it on methods that throw it. That's fine. I generally prefer checked exceptions, but if the AppEngine team prefers unchecked exceptions, I'm happy to make this change. > - If you do the above, you could make the Deferrable interface extend > Runnable, as suggested in the meeting. I'm not sure that's appropriate, > since the implications of Runnable are different. I think Runnable is not appropriate. I also looked at Callable, but in the end thought a new interface--Deferrable--was the best option. > - I'm not sure there's any need to be able to pass arguments to the > Deferrable, since users will already have to declare a deferrable class and > instantiate it. I'm open to convincing, though. I put the arguments there to mimic the Python API and then realized later they're not really needed. Removing the arguments also simplifies the code by eliminating the need for the TaskHolder class--the Deferrable class could be serialized directly. I'm happy to remove the arguments if that's what the AppEngine team decides is best. > - Have you tested tasks of size exactly MaxTaskSizeBytes? At least in > Python, the actual limit seems to include some overhead that varies from > task to task. No, I haven't tested this yet. > - If payload isn't an instance of TaskHolder, the task will silently return > - it should log an error. I think the only way payload won't be an instance of TaskHolder is if the deserialize() method returns null, in which case an error has already been logged. But I'll double-check this. > Are you interested in having this included in the official SDK? > -Nick > On Sat, Oct 31, 2009 at 7:08 PM, Vince Bonfanti <[email protected]> wrote: >> >> This looked like an interesting problem, and I already had most of the >> pieces in place, so here's my first attempt, which is implemented in a >> single class (also attached, along with some test files): >> >> >> http://code.google.com/p/gaevfs/source/browse/trunk/src/com/newatlanta/appengine/taskqueue/Deferred.java >> >> I'm more than happy to contribute this for inclusion in the SDK. >> >> Some caveats: >> >> 1) Because of issue #2097 >> (http://code.google.com/p/googleappengine/issues/detail?id=2097), this >> doesn't work on the development server (it does work in production). >> So go star that issue! >> >> 2) I've only done minimal testing on the production server (see the >> attached test files). >> >> 3) This post is the only documentation that's currently available. >> >> First, add the following your your web.xml: >> >> <servlet> >> <servlet-name>Deferred</servlet-name> >> >> <servlet-class>com.newatlanta.appengine.taskqueue.Deferred</servlet-class> >> </servlet> >> <servlet-mapping> >> <servlet-name>Deferred</servlet-name> >> <url-pattern>/_ah/queue/deferred</url-pattern> >> </servlet-mapping> >> >> Second, define the "deferred" queue within queue.xml (use whatever >> rate you want): >> >> <queue> >> <name>deferred</name> >> <rate>10/s</rate> >> </queue> >> >> Next, create a class that implements the >> com.newatlanta.appengine.taskqueue.Deferred.Deferrable interface; the >> "doTask()" method of this class is where you implement your task >> logic. >> >> Then, invoke the com.newatlanta.appengine.taskqueue.Deferred.defer() >> method to queue up your task: >> >> TestDeferred testDeferred = new TestDeferred(); // implements >> Deferrable >> Deferred.defer( testDeferred, "one", "two", "three", 1, 2, 3 ); >> >> (Note that it would be possible to pass arguments as attributes to >> your Deferrable instance, rather than using varargs; I'm not sure it >> makes much difference which you choose). >> >> Just as for the Python implementation, if the arguments size exceeds >> 10KB, the arguments are stored in a datastore entity, which is then >> deleted when the task is executed. Also, your doTask() method can >> throw a PermanentTaskFailure exception to halt retries; any other >> exceptions cause the task to be retried. >> >> Let me know if you find this useful, have any questions or encounter >> any problems. >> >> Vince >> >> On Fri, Oct 30, 2009 at 6:13 PM, Jason (Google) <[email protected]> >> wrote: >> > Hi David. This may be coming to Java eventually, but it hasn't been >> > started >> > yet. If you or anyone else is interested in contributing, let me know. >> > >> > - Jason >> > >> > On Wed, Oct 28, 2009 at 7:52 AM, David Chandler <[email protected]> >> > wrote: >> >> >> >> Re: http://code.google.com/appengine/articles/deferred.html >> >> >> >> Will this be coming to AppEngine for Java? >> >> >> >> David Chandler >> >> http://turbomanage.wordpress.com >> >> >> >> >> > >> > >> > > >> > >> >> > > > > -- > Nick Johnson, Developer Programs Engineer, App Engine > Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration Number: > 368047 > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. 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