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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: timing issue?
Date Wed, 21 Jul 2010 08:21:28 GMT
Or you can use SelectQuery with prefetches for relationships and cache  
groups plus entity listeners flushing appropriate cache groups on  
commit. This requires more manual setup and planning upfront, but  
better scales in terms of clustering, and gives better consistency  
(not only individual objects are refreshed, but also all cached query  
lists).

Andrus


On Jul 21, 2010, at 11:11 AM, Andrus Adamchik wrote:

> Hi Bryan,
>
> There can definitely be a small delay updating a peer context in the  
> same JVM with the commit data. And this is probably what you are  
> observing in the test (adding a delay gives all DataContexts a  
> chance to digest the event). If the relationship hasn't been  
> refreshed for an hour, this is caused by something else... My guess  
> is that the Company object in a peer context had modifications of  
> its own, so Cayenne bailed on merging the changes into it. There is  
> a code in ObjectStore responsible for merging to-many:
>
> void processIndirectlyModifiedIDs(Collection indirectlyModifiedIDs) {
>       Iterator indirectlyModifiedIt =  
> indirectlyModifiedIDs.iterator();
>       while (indirectlyModifiedIt.hasNext()) {
>           ObjectId oid = (ObjectId) indirectlyModifiedIt.next();
>
>           // access object map directly - the method should be  
> called in a synchronized
>           // context...
>           final DataObject object = (DataObject) objectMap.get(oid);
>
>           if (object == null
>                   || object.getPersistenceState() !=  
> PersistenceState.COMMITTED) {
>               continue;
>           }
> ....
> }
>
> One possible way around it is to invalidate Company object after  
> commit (then on next read it will refetch its relationship).
>
> Andrus
>
> On Jul 20, 2010, at 4:05 PM, Bryan Lewis wrote:
>
>> We released a new internal web app at the start of the month and  
>> we've
>> noticed some troublesome behavior.  After the insertion or deletion  
>> of an
>> object, a to-many relationship can occasionally get out of sync.  For
>> example, we have a Company entity with a to-many relationship to  
>> Task. After
>> the user adds a task and returns to the task list page, the new  
>> object
>> doesn't appear.  Sometimes.  I've been working around it by adding  
>> explicit
>> refetches in the list pages.
>>
>> I've tried to boil it down to a reproducible test case.  The code  
>> below
>> simply adds and deletes a thousand objects and checks that the size  
>> of the
>> list is correct in a different DataContext.  One of the assertions  
>> will fail
>> at some point in the test.  I tried it with and without OSCache and  
>> the
>> error happens with both.
>>
>> I wondered if it might be some kind of timing issue.  If I added a
>> one-second pause whenever the lists disagreed, that was enough to  
>> get them
>> back in sync.
>>
>> I'm not sure this completely explains the behavior we've been  
>> seeing. We
>> haven't been hitting the database that hard, with only about a half- 
>> dozen
>> users at any one time.  Yesterday we had a case where one user's  
>> insertion
>> didn't appear in another user's list almost an hour later.  It's a  
>> start for
>> discussion.  It would be good news if I'm missing something.
>>
>>
>>  private static final int cRuns = 1000;
>>
>>  private Employee user;
>>  private RDTaskType taskType;
>>
>>  private org.apache.cayenne.access.DataContext createDataContext()
>>  {
>>      Configuration config = Configuration.getSharedConfiguration();
>>      DataDomain domain = config.getDomain();
>>      return domain.createDataContext();
>>  }
>>
>>  void onActionFromTestCaching()
>>  {
>>      DataContext dc = createDataContext();
>>      DataContext dc2 = createDataContext();
>>
>>      // Get a few objects needed to populate new tasks.
>>      user = DataObjectUtils.objectForPK(dc, Employee.class, 312);
>>      taskType = DataObjectUtils.objectForPK(dc, RDTaskType.class,
>> "CLIOR");
>>
>>      // A Company is the source of the to-many relationship.  Get the
>> same
>>      // one in two DataContexts.
>>      Company company = DataObjectUtils.objectForPK(dc, Company.class,
>> 5000);
>>      Company company2 = (Company)  
>> dc2.localObject(company.getObjectId(),
>> null);
>>
>>      int nTasksStart = company.getTasks().size();
>>
>>      for (int i = 0; i < cRuns; i++) {
>>          int nTasks = company.getTasks().size();
>>          assert nTasks == nTasksStart + i : nTasks;
>>
>>          int nTasks2 = company2.getTasks().size();
>>          if (nTasks2 != nTasks) {
>>              debug("nTasks2 was " + nTasks2);
>>              pause();
>>              nTasks2 = company2.getTasks().size();
>>              debug("nTasks2 now " + nTasks2);
>>          }
>>          assert nTasks2 == nTasks : "nTasks = " + nTasks + ",  
>> nTasks2 = "
>> + nTasks2; // sometimes fails
>>
>>          insertTask(company);
>>      }
>>
>>      List<Task> tasks = company.getTasks();
>>      nTasksStart = tasks.size();
>>
>>      for (int i = 0; i < cRuns; i++) {
>>          int nTasks = company.getTasks().size();
>>          assert nTasks == nTasksStart - i : nTasks;
>>
>>          int nTasks2 = company2.getTasks().size();
>>          if (nTasks2 != nTasks) {
>>              debug("nTasks2 was " + nTasks2);
>>              pause();
>>              nTasks2 = company2.getTasks().size();
>>              debug("nTasks2 now " + nTasks2);
>>          }
>>          assert nTasks2 == nTasks : "nTasks = " + nTasks + ",  
>> nTasks2 = "
>> + nTasks2;
>>
>>          deleteTask(tasks.get(nTasks - 1));
>>      }
>>  }
>>
>>  private org.apache.cayenne.access.DataContext createDataContext()
>>  {
>>      Configuration config = Configuration.getSharedConfiguration();
>>      DataDomain domain = config.getDomain();
>>      return domain.createDataContext();
>>  }
>>
>>  private void insertTask(Company company)
>>  {
>>      Date now = new java.util.Date();
>>      DataContext dc = (DataContext) company.getObjectContext();
>>
>>      Task task = dc.newObject(Task.class);
>>      task.setCreatedBy(user);
>>      task.setLastModifiedBy(user);
>>      task.setCreatedWhen(now);
>>      task.setTargetDate(now);
>>      task.setTimeWhen(now);
>>      task.setCompany(company);
>>      task.setAssignedTo(user);
>>      user.addToTasks(task);
>>      task.setType(taskType);
>>
>>      try {
>>          dc.commitChanges();
>>      }
>>      catch (CayenneRuntimeException e) {
>>          e.printStackTrace();
>>      }
>>  }
>>
>>  private void deleteTask(Task task)
>>  {
>>      DataContext dc = (DataContext) task.getObjectContext();
>>      dc.deleteObject(task);
>>
>>      try {
>>          dc.commitChanges();
>>      }
>>      catch (CayenneRuntimeException e) {
>>          e.printStackTrace();
>>      }
>>  }
>>
>>  private long pauseMillis = 1000;
>>
>>  private void pause()
>>  {
>>      if (pauseMillis > 0) {
>>          debug("pausing...");
>>          try {
>>              Thread.sleep(pauseMillis);
>>          }
>>          catch (InterruptedException ex) {
>>              ex.printStackTrace();
>>          }
>>      }
>>  }
>
>


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