Re: [jboss-dev] Oops, javax.naming.spi.* is dependent on Hashtable, this will make it difficult to change the JBoss jndi naming service to use ConcurrentHashMap instead of Hashtable...
On Wed, 2007-07-11 at 11:58 -0400, Scott Marlow wrote:
Hi Adrian,
The 2-3 second contention that I'm seeing is on the following call stack:
"PooledInvokerThread-192.169.1.2: java.util.Hashtable.get :335
PooledInvokerThread-192.169.1.2: org.jnp.interfaces.NamingContext.useAbsoluteName :1090
PooledInvokerThread-192.169.1.2: org.jnp.interfaces.NamingContext.getObjectInstance
:1123
PooledInvokerThread-192.169.1.2:
org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure :1142
PooledInvokerThread-192.169.1.2: org.jnp.interfaces.NamingContext.lookup :705
PooledInvokerThread-192.169.1.2: org.jnp.interfaces.NamingContext.lookup :587
PooledInvokerThread-192.169.1.2: javax.naming.InitialContext.lookup :351
PooledInvokerThread-192.169.1.2:
org.hibernate.transaction.JTATransactionFactory.isTransactionInProgress :83
PooledInvokerThread-192.169.1.2: org.hibernate.jdbc.JDBCContext.isTransactionInProgress
:180
PooledInvokerThread-192.169.1.2:
org.hibernate.jdbc.JDBCContext.registerSynchronizationIfPossib :158
PooledInvokerThread-192.169.1.2:
org.hibernate.impl.SessionImpl.checkTransactionSynchStatus :1850
PooledInvokerThread-192.169.1.2: org.hibernate.impl.SessionImpl.getEntityMode :1274
PooledInvokerThread-192.169.1.2: org.hibernate.engine.StatefulPersistenceContext.addEntry
:415
PooledInvokerThread-192.169.1.2:
org.hibernate.engine.StatefulPersistenceContext.addEntity :382
PooledInvokerThread-192.169.1.2: org.hibernate.engine.TwoPhaseLoad.addUninitializedEntity
:240
PooledInvokerThread-192.169.1.2: org.hibernate.loader.Loader.loadFromResultSet :1358
PooledInvokerThread-192.169.1.2: org.hibernate.loader.Loader.instanceNotYetLoaded :1300
PooledInvokerThread-192.169.1.2: org.hibernate.loader.Loader.getRow :1197
..."
I am looking at changing the Hashtable to a ConcurrentHashMap which
could help some applications run more concurrently.
This just looks like a bug in Hibernate.
It is caching the naming context in the JTATransactionFactory
and then using it concurrently across threads, without
the required synchronization.
This probably only works by luck, because it is looking up in
"java:comp" for the UserTransaction which is a read only context
constructed at deployment time and is therefore unlikely
to have concurrency problems.
I'm sure if this class was changed to create a new initial context
for each request you wouldn't see the contention, but that
might not be very efficient either. Depends how often the
isTransactionInProgress() is invoked.
I don't see why it isn't caching the UserTransaction instead anyway.
It's probably because some people use Hibernate across transaction
demarcation boundaries in at least dubious, if not broken ways. :-)
--
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Adrian Brock
Chief Scientist
JBoss, a division of Red Hat
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