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DrVillo
 Post subject: StatelessSession & non thread-safe access?!
PostPosted: Fri Mar 24, 2006 7:30 am 
Newbie

Joined: Fri Dec 23, 2005 7:54 am
Posts: 12
Hi

For a certain part of the service I'm working on I need to use a StatelessSession.
I have to make a slightly simple query, that nevertheless I can't get working, if not using a normal Session...
Things have been working fine up to now, but I'm currently stuck with the following

Code:
        StatelessSession session = sessionFactory.openStatelessSession();
        Transaction tx = session.beginTransaction();

        Collection<Measure> mm;
        int loaded = 0;
        try {

            mm = dao.find(tb, server, tmStart, tmEnd, session);
            loaded = mm.size();
            tx.commit();


        } catch (Exception e) {
            if (tx != null) tx.rollback();

        } finally {
            session.close();
            long endTime = System.currentTimeMillis() - startTime;
            logger.info("Queried: " + loaded + " time: " + endTime);
        }


where the dao.find() method looks like:

Code:

public Collection<Measure> find(TestBox tb, Server s, long tStart, long tEnd,StatelessSession sess) {
        s = DomainCache.getInstance().getServer(s);
        tb = DomainCache.getInstance().getTestBox(tb);

        logger.debug("Query criteria: "+tb+", "+s+", "+tStart+", "+tEnd);

        Query query = sess.createQuery("from Measure m where m.testBox=? and m.server=? and" +
                " m.tm>=? and m.tm<=? order by m.tm").
                setParameter(0, tb).
                setParameter(1, s).
                setParameter(2, tStart).
                setParameter(3, tEnd);

        if(maxResultSize>0)
            query.setMaxResults(maxResultSize);



        return query.list();
    }



However I get the following behavior when list() gets called...


Code:

12:18:21,435 DEBUG Loader:1164 - result row: EntityKey[net.ripe.dnsmon.domain.Measure#346]
12:18:21,436 DEBUG Loader:1347 - Initializing object from ResultSet: [net.ripe.dnsmon.domain.Measure#346]
12:18:21,437 DEBUG AbstractEntityPersister:1860 - Hydrating entity: [net.ripe.dnsmon.domain.Measure#346]
12:18:21,437 DEBUG IntegerType:123 - returning '138' as column: SERVER6_5_
12:18:21,438 DEBUG IntegerType:123 - returning '2' as column: QUERY7_5_
12:18:21,439 DEBUG IntegerType:123 - returning '1' as column: TESTBOX8_5_
12:18:21,439 DEBUG LongType:123 - returning '1136073700' as column: TM5_
12:18:21,440 DEBUG ShortType:123 - returning '1' as column: attempt5_
12:18:21,441 DEBUG StringType:123 - returning 'k1.ams-ix' as column: answer5_
12:18:21,442 DEBUG FloatType:123 - returning '0.001891' as column: delay5_
12:18:21,443 DEBUG Loader:709 - done processing result set (101 rows)
12:18:21,444 DEBUG AbstractBatcher:334 - about to close ResultSet (open ResultSets: 1, globally: 1)
12:18:21,444 DEBUG AbstractBatcher:319 - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
12:18:21,445 DEBUG AbstractBatcher:470 - closing statement
12:18:21,451 DEBUG Loader:839 - total objects hydrated: 101
12:18:21,453 DEBUG TwoPhaseLoad:104 - resolving associations for [net.ripe.dnsmon.domain.Measure#1]
12:18:21,453 DEBUG AbstractEntityPersister:2723 - Fetching entity: [net.ripe.dnsmon.domain.Server#138]
12:18:21,454 DEBUG Loader:1777 - loading entity: [net.ripe.dnsmon.domain.Server#138]
12:18:21,455 DEBUG AbstractBatcher:311 - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
12:18:21,456 DEBUG SQL:346 - select server0_.id as id0_0_, server0_.ADDRESS as ADDRESS0_0_, server0_.NAME as NAME0_0_ from SERVERS server0_ where server0_.id=?
Hibernate: select server0_.id as id0_0_, server0_.ADDRESS as ADDRESS0_0_, server0_.NAME as NAME0_0_ from SERVERS server0_ where server0_.id=?
12:18:21,457 DEBUG AbstractBatcher:424 - preparing statement
12:18:21,460 DEBUG IntegerType:79 - binding '138' to parameter: 1
12:18:21,464 DEBUG AbstractBatcher:327 - about to open ResultSet (open ResultSets: 0, globally: 0)
12:18:21,465 DEBUG Loader:682 - processing result set
12:18:21,465 DEBUG Loader:687 - result set row: 0
12:18:21,466 DEBUG Loader:1164 - result row: EntityKey[net.ripe.dnsmon.domain.Server#138]
12:18:21,467 DEBUG Loader:1347 - Initializing object from ResultSet: [net.ripe.dnsmon.domain.Server#138]
12:18:21,468 DEBUG AbstractEntityPersister:1860 - Hydrating entity: [net.ripe.dnsmon.domain.Server#138]
12:18:21,469 DEBUG StringType:116 - returning null as column: ADDRESS0_0_
12:18:21,471 DEBUG StringType:123 - returning 'k.root-servers.net' as column: NAME0_0_
12:18:21,474 DEBUG Loader:709 - done processing result set (1 rows)
12:18:21,475 DEBUG AbstractBatcher:334 - about to close ResultSet (open ResultSets: 1, globally: 1)
12:18:21,476 DEBUG AbstractBatcher:319 - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
12:18:21,477 DEBUG AbstractBatcher:470 - closing statement
12:18:21,478 DEBUG Loader:839 - total objects hydrated: 1
12:18:21,479 DEBUG TwoPhaseLoad:104 - resolving associations for [net.ripe.dnsmon.domain.Server#138]
12:18:21,480 DEBUG CollectionLoadContext:141 - creating collection wrapper:[net.ripe.dnsmon.domain.Server.authorities#138]
12:18:21,481 DEBUG TwoPhaseLoad:203 - done materializing entity [net.ripe.dnsmon.domain.Server#138]
12:18:21,482 DEBUG Loader:1808 - done entity load
12:18:21,483 DEBUG AbstractEntityPersister:2723 - Fetching entity: [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,484 DEBUG Loader:1777 - loading entity: [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,485 DEBUG AbstractBatcher:311 - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
12:18:21,486 DEBUG SQL:346 - select querytype0_.CODE as CODE4_0_, querytype0_.type as type4_0_ from QUERY_TYPES querytype0_ where querytype0_.CODE=?
Hibernate: select querytype0_.CODE as CODE4_0_, querytype0_.type as type4_0_ from QUERY_TYPES querytype0_ where querytype0_.CODE=?
12:18:21,487 DEBUG AbstractBatcher:424 - preparing statement
12:18:21,490 DEBUG IntegerType:79 - binding '2' to parameter: 1
12:18:21,491 DEBUG AbstractBatcher:327 - about to open ResultSet (open ResultSets: 0, globally: 0)
12:18:21,492 DEBUG Loader:682 - processing result set
12:18:21,493 DEBUG Loader:687 - result set row: 0
12:18:21,494 DEBUG Loader:1164 - result row: EntityKey[net.ripe.dnsmon.domain.QueryType#2]
12:18:21,495 DEBUG Loader:1347 - Initializing object from ResultSet: [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,496 DEBUG AbstractEntityPersister:1860 - Hydrating entity: [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,497 DEBUG StringType:123 - returning 'id.server' as column: type4_0_
12:18:21,498 DEBUG Loader:709 - done processing result set (1 rows)
12:18:21,499 DEBUG AbstractBatcher:334 - about to close ResultSet (open ResultSets: 1, globally: 1)
12:18:21,500 DEBUG AbstractBatcher:319 - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
12:18:21,501 DEBUG AbstractBatcher:470 - closing statement
12:18:21,502 DEBUG Loader:839 - total objects hydrated: 1
12:18:21,503 DEBUG TwoPhaseLoad:104 - resolving associations for [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,504 DEBUG TwoPhaseLoad:203 - done materializing entity [net.ripe.dnsmon.domain.QueryType#2]
12:18:21,507 DEBUG Loader:1808 - done entity load
12:18:21,508 DEBUG AbstractEntityPersister:2723 - Fetching entity: [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,509 DEBUG Loader:1777 - loading entity: [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,510 DEBUG AbstractBatcher:311 - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
12:18:21,511 DEBUG SQL:346 - select testbox0_.id as id7_0_, testbox0_.alias as alias7_0_, testbox0_.name as name7_0_ from TESTBOXES testbox0_ where testbox0_.id=?
Hibernate: select testbox0_.id as id7_0_, testbox0_.alias as alias7_0_, testbox0_.name as name7_0_ from TESTBOXES testbox0_ where testbox0_.id=?
12:18:21,512 DEBUG AbstractBatcher:424 - preparing statement
12:18:21,513 DEBUG IntegerType:79 - binding '1' to parameter: 1
12:18:21,515 DEBUG AbstractBatcher:327 - about to open ResultSet (open ResultSets: 0, globally: 0)
12:18:21,516 DEBUG Loader:682 - processing result set
12:18:21,517 DEBUG Loader:687 - result set row: 0
12:18:21,518 DEBUG Loader:1164 - result row: EntityKey[net.ripe.dnsmon.domain.TestBox#1]
12:18:21,519 DEBUG Loader:1347 - Initializing object from ResultSet: [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,519 DEBUG AbstractEntityPersister:1860 - Hydrating entity: [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,520 DEBUG StringType:123 - returning 'tt01(NL)' as column: alias7_0_
12:18:21,523 DEBUG StringType:123 - returning 'tt01.ripe.net' as column: name7_0_
12:18:21,523 DEBUG Loader:709 - done processing result set (1 rows)
12:18:21,524 DEBUG AbstractBatcher:334 - about to close ResultSet (open ResultSets: 1, globally: 1)
12:18:21,525 DEBUG AbstractBatcher:319 - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
12:18:21,526 DEBUG AbstractBatcher:470 - closing statement
12:18:21,527 DEBUG Loader:839 - total objects hydrated: 1
12:18:21,528 DEBUG TwoPhaseLoad:104 - resolving associations for [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,528 DEBUG TwoPhaseLoad:203 - done materializing entity [net.ripe.dnsmon.domain.TestBox#1]
12:18:21,529 DEBUG Loader:1808 - done entity load
12:18:21,530 DEBUG TwoPhaseLoad:203 - done materializing entity [net.ripe.dnsmon.domain.Measure#1]
12:18:21,534 ERROR AssertionFailure:22 - an assertion failure occured (this may indicate a bug in Hibernate, but is more likely due to unsafe use of the session)
org.hibernate.AssertionFailure: possible non-threadsafe access to the session
        at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:97)
        at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:842)
        at org.hibernate.loader.Loader.doQuery(Loader.java:717)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
        at org.hibernate.loader.Loader.doList(Loader.java:2150)
        at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029)
        at org.hibernate.loader.Loader.list(Loader.java:2024)
        at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:369)
        at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:300)
        at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:146)
        at org.hibernate.impl.StatelessSessionImpl.list(StatelessSessionImpl.java:368)
        at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
        at net.ripe.dnsmon.measures.dao.MeasureDAO.find(MeasureDAO.java:170)
        at net.ripe.dnsmon.measures.MeasureFacade.getMeasures(MeasureFacade.java:216)
        at net.ripe.dnsmon.measures.MeasureFacade.main(MeasureFacade.java:195)
12:18:21,542 DEBUG JDBCTransaction:152 - rollback
12:18:21,543 DEBUG JDBCTransaction:163 - rolled back JDBC Connection
12:18:21,544 DEBUG JDBCContext:207 - after transaction completion
12:18:21,544 DEBUG ConnectionManager:296 - aggressively releasing JDBC connection
12:18:21,545 DEBUG ConnectionManager:333 - closing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
12:18:21,552 DEBUG DriverManagerConnectionProvider:129 - returning connection to pool, pool size: 1
12:18:21,553 DEBUG ConnectionManager:267 - connection already null in cleanup : no action




The above snippet shows the activity starting from the last record returned by list(). Basically it shows hibernate getting the record, trying to resolve the associations ( I don't know why...shouldn't StatelessSession ignore them?) and materialazing them. Then it hangs materializing the Measure instance...


The generated SQL (show_sql=true):
This is the query generated by the find() method:
Code:
select measure0_.MEASURE_ID as MEASURE1_5_, measure0_.SERVER_ID as SERVER6_5_, measure0_.QUERY_CODE as QUERY7_5_, measure0_.TESTBOX_ID as TESTBOX8_5_, measure0_.TM as TM5_, measure0_.attempt as attempt5_, measure0_.answer as answer5_, measure0_.delay as delay5_ from MEASURES measure0_ where measure0_.TESTBOX_ID=? and measure0_.SERVER_ID=? and measure0_.TM>=? and measure0_.TM<=? order by measure0_.TM


That is, nothing new here. Nevertheless I don't understand why


I don't know if this could be the problem but in the same instance that allocates the StatelessSession and manage the transaction, there is an init() that makes use of a normal Session.

Code:
    private void init() {

        Session s = sessionFactory.getCurrentSession();
        s.beginTransaction();
        DomainCache.getInstance().initCache(s);
        s.getTransaction().commit();
        s.close();
        logger.debug(DomainCache.getInstance().toString());

    }


But I don't see how invoking this could/should interfere with the StatelessSession usage, even if the instances contained in DomainCache are used there. Beside this the same pattern (calling init() and then using a stateless session using DomainCache) works when doing batch updates.


I have to say that I'm stuck...I hope that somebody will enlighten me because I'm obviously doing something wrong but I can't figure out what:(


Thanks everybody, sorry for the long post

Francesco
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DrVillo
 Post subject:
PostPosted: Fri Mar 24, 2006 10:20 am 
Newbie

Joined: Fri Dec 23, 2005 7:54 am
Posts: 12
Update:

I've been debugging the list() invocation;
for some reason the first record is loaded correctly, i.e the Measure instance and its associations are materialized. The problem occurs on the second Measure instance that gets at

Code:
TwoPhaseLoad.initializeEntity()


at this point the PersistenceContext is empty.

This summarizes:


1. Call to TwoPhaseLoad.initializeEntity() with the first Measure record as entity: PersistenceContext holds a list of the returned records to be materialized
2. Call to TwoPhaseLoad.initializeEntity() with its associations as entities: PersistenceContext holds references to associations
3. Call to TwoPhaseLoad.initializeEntity() with the second Measure record as entity: PersistenceContext has empty Maps.

I've tried to reproduce with a simpler object (still with associations) without luck; nevertheless I reproduce the problem with these lines now:

Code:
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

        StatelessSession s = sessionFactory.openStatelessSession();

        s.beginTransaction();

        s.createQuery("from Measure q").setMaxResults(10).list();

        s.getTransaction().commit();

        s.close();


So there is no possible interference with stale Stateful sessions...
Hints?
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DrVillo
 Post subject:
PostPosted: Fri Mar 24, 2006 12:15 pm 
Newbie

Joined: Fri Dec 23, 2005 7:54 am
Posts: 12
Update 2:
I have been able to get a workaround.

it happens that the following:

Code:
        Criteria query = sess.createCriteria(Measure.class).
                add(Restrictions.eq("server",s)).
                add(Restrictions.eq("testBox",tb)).
                add(Restrictions.le("tm",tEnd)).
                add(Restrictions.ge("tm",tStart));
        if(maxResultSize>0)
            query.setMaxResults(10);



        return query.list();


works. Nevertheless I don't know what to think of the resulting query.
At this point I'd like to know why this difference in behavior. The two queries look pretty much the same in semantics.
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mellster
 Post subject: Re: StatelessSession & non thread-safe access?!
PostPosted: Wed May 17, 2006 7:55 pm 
Newbie

Joined: Fri Apr 15, 2005 7:52 pm
Posts: 13
We encounter exactly the same problem as the original poster. When using a StatelessSession for HQL queries, hibernate seems to try loading collections/entities and associates a stateful persistence context with the StatelessSession (which both contradict its documentation) before finally crashing and burning in the TwoPhaseLoad. The simple example given by the original poster above should quickly illustrate the problem. This looks like a significant problem to me which will hopefully be addressed soon. TIA!
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aaime
 Post subject:
PostPosted: Mon May 29, 2006 5:54 am 
Beginner
Beginner

Joined: Fri Apr 09, 2004 12:47 pm
Posts: 36
I'm seeing this problem as well. Nobody has any idea of what's going on?
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lgommers
 Post subject:
PostPosted: Thu Dec 27, 2007 6:26 am 
Newbie

Joined: Thu Dec 27, 2007 6:21 am
Posts: 1
In my case I had a lazy="false" association specified on my bean. If I explicitly specify the left join in the query I don't get the exception any more.
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pvradhakrishna
 Post subject: how to fetch just parent and leave the lazy="false" entities
PostPosted: Thu Jul 16, 2009 12:03 pm 
Regular
Regular

Joined: Tue Feb 19, 2008 6:05 pm
Posts: 82
I see a patch at
http://opensource.atlassian.com/project ... e/HHH-3220

but is there a way to use Criteria or HQL queries, to just bring the parent entity and leave the related entities set as lazy="false" in the parent entities mapping file. I have performance issues and am planning to use StatelessSession, but cannot get it to work as it throws the exception whether I use the criteria query or the HQL query.

org.hibernate.AssertionFailure: possible non-threadsafe access to the session
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:100)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:854)
at org.hibernate.loader.Loader.doQuery(Loader.java:729)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
at org.hibernate.loader.Loader.doList(Loader.java:2220)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2104)
at org.hibernate.loader.Loader.list(Loader.java:2099)
at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94)
at org.hibernate.impl.StatelessSessionImpl.list(StatelessSessionImpl.java:537)
at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283)
....

So the question again is, is there a way to specify run time not to eager fetch the lazy="false" entities by any chance?
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pvradhakrishna
 Post subject: Re: how to fetch just parent and leave the lazy="false" entities
PostPosted: Thu Jul 16, 2009 12:17 pm 
Regular
Regular

Joined: Tue Feb 19, 2008 6:05 pm
Posts: 82
I guess I could write my HQL as

Code:
select currentEntity from  CurrentEntity currentEntity left join currentEntity.someEagerParent


but this also throws the exception.

How else,
Krishna
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stliu
 Post subject: Re: how to fetch just parent and leave the lazy="false" entities
PostPosted: Thu Apr 01, 2010 6:03 am 
Hibernate Team
Hibernate Team

Joined: Tue Aug 11, 2009 2:26 am
Posts: 29
pvradhakrishna wrote:
I guess I could write my HQL as

Code:
select currentEntity from  CurrentEntity currentEntity left join currentEntity.someEagerParent




would you please try
Code:
select currentEntity from CurrentEntity currentEntity join fetch currentEntity.someEagerParent
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Wallenstein
 Post subject: Re: StatelessSession & non thread-safe access?!
PostPosted: Mon Jul 22, 2013 9:36 am 
Newbie

Joined: Thu Sep 13, 2012 6:46 am
Posts: 2
Just in case:

The problem is still there in hibernate 3.6.10.

I have solved it by setting the fetchType to LAZY. Which was OK in my situation.

Alternatively I guess, I could have included an explicit "... left join fetch ..." into the query.

Wallenstein
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