webobjects-dev@wocommunity.org Mailing List Archive

Hi OC,

Check to be sure your import task is only started after the app has finished loading, not during the launch of the app. If you call too early in the startup phase your ModelGroups, etc, may not be setup yet. That’s what it sort of looks like from your stack trace because you have a null pointer inside of EOModelGroup which is a NeXT/Apple object, not even a WOnder one.

If you double check and are sure you don’t kick off a concurrent thread before the app has finished loading… then I’m not sure. You may have to revisit your use of the ERX messaging coordinators. I’ve never used them so I don’t have experience to share. From where I stand they sound “cool” but I don’t get the use case. I get that people want “fresh” data and if every edit messages to all the other ObjectStoreCoordinators then everybody is fresh all the time! Cool! but at what cost? Does every instance need to fault in objects that people may never see? If someone is editing the same data, and they get an update from some other thread, what then? who wins? Chatter is expensive on CPU / network too. Seems to me that if people want “fresh” then the best thing is to not sync but to get fresh data on the page that you are at by setting the timestamp lag to something small like 2 seconds. For a statistics page maybe avoid EOF altogether, use a direct fetch of SQL.

On Mar 21, 2021, at 12:01 AM, OCsite <webobjects-dev@wocommunity.org> wrote:

Hi there,

occasionally (not too often), we are running a background import task, which uses its own EO stack: at launch, it creates a new EOObjectStoreCoordinator (and for it it creates an ERXEC and uses it to import data). When done and saved, the coordinator is disposed and released. The rationale is that the imported data might be big and we don't want to limit normal workers processing to wait until the import saves its results into the database.

For a long long time it worked reliably and without a glitch.

Lately, it often (though by far not each time!) happens that

(i) a save in the background task reports the following exception:

===
04:38:38.600 ERROR java.lang.NullPointerException //log:er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer [ERXOSCProcessChanges]
NullPointerException
at com.webobjects.eoaccess.EOModelGroup.modelGroupForObjectStoreCoordinator(EOModelGroup.java:795)
at er.extensions.eof.ERXEOAccessUtilities.databaseContextForEntityNamed(ERXEOAccessUtilities.java:1086)
at er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue._process(ERXObjectStoreCoordinatorSynchronizer.java:509)
at er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue.process(ERXObjectStoreCoordinatorSynchronizer.java:540)
at er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue.run(ERXObjectStoreCoordinatorSynchronizer.java:617)
... skipped 1 stack elements
===

(ii) after that, usually no more exceptions are reported, but the ERXObjectStoreCoordinatorSynchronizer does not seem to work properly anymore, and it often happens that the changes done in the background task are not visible in the main OSC for awhile.

From the user's perspective it usually means that the import is finished, but the imported data is not visible for a long long time (does not seem to be just a fetchTimestampLag, for newly logged-in users with their new sessions and new ECs still don't see the imported data for awhile. Frankly, I can't see what the H. might be the culprit :/ )

(iii) another problem which seems to be also caused (perhaps indirectly) by the above exception is that the application cannot be normally quit from JavaMonitor, reporting upon an attempt

===
04:33:43.441 ERROR Exception caught: null
... ...
IllegalStateException: Attempted to stop the ProcessChangesQueue when it wasn't already running
at er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer$ProcessChangesQueue.stop(ERXObjectStoreCoordinatorSynchronizer.java:637)
at er.extensions.eof.ERXObjectStoreCoordinatorSynchronizer.stopRemoteSynchronizer(ERXObjectStoreCoordinatorSynchronizer.java:132)
... skipped 8 stack elements
at er.extensions.appserver.ERXApplication.terminate(ERXApplication.java:2861)
... ...
===

Any idea what might be the culprit and how to fix it?

Thanks and all the best,
OC