[hibernate-dev] Missing transaction hangs the testsuite

Sanne Grinovero sanne at hibernate.org
Fri Jul 17 12:11:36 EDT 2015 

On 17 July 2015 at 16:25, Steve Ebersole <steve at hibernate.org> wrote:
> It would seem that this is a regression with ORM, I agree.  However, we do
> not know how recent of a regression.  And that is the problem.  We have no
> idea how far back to look.  Because the ORM CI jobs against MySQL,
> PostrgreSQL, Oracle, etc have not been running for many months.  IIRC even
> when they were running on the old CI servers we had problems with those jobs
> that were not looked at for some time.

Sure, same problem here: not run these tests for months, and you're
right I could do a quick check on a slightly older branch which is
using ORM 4.3 and I have the same problem.

> As far as what you see, I am not convinced it is what you think it is in
> terms of auto-commit for queries run outside of a transaction.  This part
> has not changed in 5.0.  Assuming you are using the "built in Connection
> pool", there is a setting that controls the auto-commit mode of the
> connections we create (hibernate.connection.autocommit).  That setting has
> always been there, and it has always defaulted to false.  This has not
> changed.  In fact the same exact code is used in 4.3 and 5.0 for creating
> these Connections:
> org.hibernate.engine.jdbc.connections.internal.BasicConnectionCreator.  The
> autoCommit value in there comes from the setting I just mentioned.  The
> logical outcome is the same even before 4.3, just that it was done
> differently.  So bottom line, if you are not seeing auto-commit on these
> Connections now, you never were.  Now it is possible that their are some
> ancillary changes that cause the lack of auto-commit to now be an issue
> where it was not before.  So first, I'd need to know whether the Connection
> here is auto-commit or is not.  From there we can start drilling down on
> what might be a cause.  But keep in mind too, that with hangs and deadlocks
> the process that hangs is often not the culprit; often it is the previous
> process that is holding locks that is the culprit.

I understand, but in this specific case I can reproduce the issue by
running a single test.
Also that psql SQL I shared clearly shows which statement is causing it to hang,
and I could fix the test by just wrapping that statement in a transaction.

>
> My case is actually different, at least on the surface.  Mine happens on
> dropping tables after the test is complete (for MySQL anyway).  Which got me
> to looking at schema export and friends and how they handle connections.
> They handle connections quite differently.  Again the same as they used to,
> but I mean very different from how sessions manage connections.  In schema
> export the connections are always set to auto-commit mode at the start of
> processing.  Then they never do anything with auto-commit afterwards.  I am
> not sure this is right.

Actually it sounds like you're having the same problem. I debugged the
PosgreSQL tests first, but I had the same on MySQL (as in the
stacktrace I shared),
and the test also hangs on schema drop.
The problem is that the schema can't be dropped because a previous
statement - from a session which is now correctly closed - is still
holding locks.

Thanks,
Sanne

>
>
>
>
> On Fri, Jul 17, 2015 at 3:51 AM Sanne Grinovero <sanne at hibernate.org> wrote:
>>
>> Thanks Steve, I wasn't sure if I had found a problem.
>> Still, it looks like the Hibernate Search tests are not benefiting
>> from auto-commit, or I wouldn't have this problem right? Our testing
>> configuration properties have been the same for years and I'm just
>> re-enabling tests which haven't been run for a while, so I suspect
>> something changed in ORM.
>>
>> I think I'd expect Hibernate ORM to automatically enable auto-commit
>> on operations not running within a transaction, to make sure all locks
>> are released when the Session is closed.
>>
>> Thanks,
>> Sanne
>>
>> On 17 July 2015 at 00:14, Steve Ebersole <steve at hibernate.org> wrote:
>> > For what it is worth, I am running into the same problems on MySQL for
>> > the
>> > ORM tests in terms of blocks on dropping tables.  PGSQL at least
>> > finishes,
>> > although I run into 55 errors which I still need to triage.
>> >
>> > On Thu, Jul 16, 2015 at 5:59 PM Steve Ebersole <steve at hibernate.org>
>> > wrote:
>> >>
>> >> There is really nothing to improve.  What would you suggest as an
>> >> improvement?  I mean from a ORM perspective, we have an ato-commit
>> >> Connection (presumably) and run a query.  How on earth would we know to
>> >> expect that the database is holding locks for that?
>> >>
>> >> As far as "requiring transactions" I have tried to fly that plane
>> >> multiple
>> >> times in the past.  I think it is absolutely ridiculous to allow these
>> >> auto-commit use cases.  In fact I personally wanted to take it to the
>> >> more
>> >> extreme case of always using JTA and simply mimicking "single resource
>> >> JTA
>> >> transactions" internally in the "JDBC transaction" case.  Gavin and I
>> >> both
>> >> did in fact.  But we got a lot of push back.
>> >>
>> >> So I am not sure exactly what the improvement here might be.  What is
>> >> it
>> >> you were thinking specifically?
>> >>
>> >> On Thu, Jul 16, 2015 at 5:36 PM Sanne Grinovero <sanne at hibernate.org>
>>
>> >> wrote:
>> >>>
>> >>> I finally got to re-enable MariaDB and PostgreSQL based tests for
>> >>> Hibernate Search - which has been running on H2 only for some months -
>> >>> and had to debug a case of a single test hanging for a long time.
>> >>>
>> >>> Essentially it would block - for hours - on the SessionFactory#close()
>> >>> method, attempting to drop the database schema with the following
>> >>> statement:
>> >>>   > alter table AncientBook_alternativeTitles drop constraint
>> >>> FKn8hhkmhof1mdgc4oi77ccq989
>> >>>
>> >>> Dumping threads I would get a very similar stack trace on both
>> >>> databases; initially I thought someone had copy/pasted a socket
>> >>> handling bug from one JDBC driver to the other ;-)
>> >>>
>> >>> The PostgreSQL testsuite hanging:
>> >>>
>> >>> "main" prio=10 tid=0x00007f0f40009000 nid=0x5f7c runnable
>> >>> [0x00007f0f48956000]
>> >>>    java.lang.Thread.State: RUNNABLE
>> >>> at java.net.SocketInputStream.socketRead0(Native Method)
>> >>> at java.net.SocketInputStream.read(SocketInputStream.java:152)
>> >>> at java.net.SocketInputStream.read(SocketInputStream.java:122)
>> >>> at
>> >>>
>> >>> org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:145)
>> >>> at
>> >>>
>> >>> org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:114)
>> >>> at
>> >>>
>> >>> org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:73)
>> >>> at org.postgresql.core.PGStream.ReceiveChar(PGStream.java:274)
>> >>> at
>> >>>
>> >>> org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1660)
>> >>> at
>> >>>
>> >>> org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
>> >>> - locked <0x00000007c11e3860> (a
>> >>> org.postgresql.core.v3.QueryExecutorImpl)
>> >>> at
>> >>>
>> >>> org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:500)
>> >>> at
>> >>>
>> >>> org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:374)
>> >>> at
>> >>>
>> >>> org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:302)
>> >>> at
>> >>>
>> >>> org.hibernate.tool.hbm2ddl.DatabaseExporter.export(DatabaseExporter.java:47)
>> >>> at
>> >>> org.hibernate.tool.hbm2ddl.SchemaExport.perform(SchemaExport.java:476)
>> >>> at
>> >>> org.hibernate.tool.hbm2ddl.SchemaExport.execute(SchemaExport.java:430)
>> >>> at org.hibernate.tool.hbm2ddl.SchemaExport.drop(SchemaExport.java:375)
>> >>> at org.hibernate.tool.hbm2ddl.SchemaExport.drop(SchemaExport.java:371)
>> >>> at
>> >>>
>> >>> org.hibernate.internal.SessionFactoryImpl.close(SessionFactoryImpl.java:1069)
>> >>> at
>> >>>
>> >>> org.hibernate.search.test.util.FullTextSessionBuilder.close(FullTextSessionBuilder.java:149)
>> >>> at
>> >>>
>> >>> org.hibernate.search.test.util.FullTextSessionBuilder$1.evaluate(FullTextSessionBuilder.java:248)
>> >>> at org.junit.rules.RunRules.evaluate(RunRules.java:20)
>> >>> at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
>> >>>
>> >>> The MariaDB testsuite hanging:
>> >>>
>> >>> "main" prio=10 tid=0x00007f8ca0009000 nid=0x4043 runnable
>> >>> [0x00007f8ca5f5c000]
>> >>>    java.lang.Thread.State: RUNNABLE
>> >>> at java.net.SocketInputStream.socketRead0(Native Method)
>> >>> at java.net.SocketInputStream.read(SocketInputStream.java:152)
>> >>> at java.net.SocketInputStream.read(SocketInputStream.java:122)
>> >>> at
>> >>>
>> >>> com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
>> >>> at
>> >>>
>> >>> com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
>> >>> at
>> >>>
>> >>> com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
>> >>> - locked <0x00000007c0baa518> (a
>> >>> com.mysql.jdbc.util.ReadAheadInputStream)
>> >>> at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2499)
>> >>> at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2952)
>> >>> at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2941)
>> >>> at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3489)
>> >>> at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
>> >>> at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
>> >>> at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2562)
>> >>> - locked <0x00000007c0baa850> (a java.lang.Object)
>> >>> at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1664)
>> >>> - locked <0x00000007c0baa850> (a java.lang.Object)
>> >>> at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1583)
>> >>> at
>> >>>
>> >>> org.hibernate.tool.hbm2ddl.DatabaseExporter.export(DatabaseExporter.java:47)
>> >>> at
>> >>> org.hibernate.tool.hbm2ddl.SchemaExport.perform(SchemaExport.java:476)
>> >>> at
>> >>> org.hibernate.tool.hbm2ddl.SchemaExport.execute(SchemaExport.java:430)
>> >>> at org.hibernate.tool.hbm2ddl.SchemaExport.drop(SchemaExport.java:375)
>> >>> at org.hibernate.tool.hbm2ddl.SchemaExport.drop(SchemaExport.java:371)
>> >>> at
>> >>>
>> >>> org.hibernate.internal.SessionFactoryImpl.close(SessionFactoryImpl.java:1069)
>> >>> at
>> >>>
>> >>> org.hibernate.search.test.util.FullTextSessionBuilder.close(FullTextSessionBuilder.java:149)
>> >>> at
>> >>>
>> >>> org.hibernate.search.test.util.FullTextSessionBuilder$1.evaluate(FullTextSessionBuilder.java:248)
>> >>> at org.junit.rules.RunRules.evaluate(RunRules.java:20)
>> >>> at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
>> >>> at
>> >>>
>> >>> org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
>> >>>
>> >>> On Gail's suggestion I went looking for database level locks; I hadn't
>> >>> thought of that as I assumed it would have timed out more aggressively
>> >>> rather than have me wait for hours.
>> >>> It turns out she was right and the reason for blocking was a simple
>> >>> "count *" query being run as a post-test assertion, which we had
>> >>> forgotten to wrap in an "open transaction & commit" statements pair.
>> >>> The test assertion would be successful, but apparently it would hold
>> >>> on the table lock beyond closing the Session and, then fail to drop
>> >>> the database at the teardown of the test.
>> >>>
>> >>> I'm wondering if this is expected, or if there's something in the new
>> >>> transaction handling code which could be improved? It took me several
>> >>> hours to figure this out; maybe I'm just not using ORM as frequently
>> >>> as once :)
>> >>> If it's this critical to have the transaction, maybe it should be
>> >>> mandatory?
>> >>>
>> >>> And as a memo for next time, this is the query to figure out details
>> >>> about locks on our testing db:
>> >>>  > SELECT * FROM pg_locks pl LEFT JOIN pg_stat_activity psa ON pl.pid
>> >>> = psa.pid where datname = 'testingdb';
>> >>>
>> >>> Thanks,
>> >>> Sanne
>> >>> _______________________________________________
>> >>> hibernate-dev mailing list
>> >>> hibernate-dev at lists.jboss.org
>> >>> https://lists.jboss.org/mailman/listinfo/hibernate-dev

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