Some kind of deadlock when trying to get session

[Jonathan Alvarsson]

I get this when I pause my locked thread in Eclipse:

waiting for: org.apache.commons.pool.impl.GenericObjectPool  (id=62)	
java.lang.Object.wait(long) line: not available [native method]	
org.apache.commons.pool.impl.GenericObjectPool(java.lang.Object).wait() line: not available	
org.apache.commons.pool.impl.GenericObjectPool.borrowObject() line: 810	
org.apache.commons.dbcp.PoolingDataSource.getConnection() line: 95	
org.apache.commons.dbcp.BasicDataSource.getConnection() line: 540	
org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(javax.sql.DataSource) line: 112	
org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy.getConnection() line: 107	
org.springframework.orm.hibernate3.TransactionAwareDataSourceConnectionProvider(org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider).getConnection() line: 81	
org.hibernate.jdbc.ConnectionManager.openConnection() line: 417	
org.hibernate.jdbc.ConnectionManager.getConnection() line: 144	
org.hibernate.jdbc.BatchingBatcher(org.hibernate.jdbc.AbstractBatcher).prepareQueryStatement(java.lang.String, boolean, org.hibernate.ScrollMode) line: 105	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.Loader).prepareQueryStatement(org.hibernate.engine.QueryParameters, boolean, org.hibernate.engine.SessionImplementor) line: 1561	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.Loader).doQuery(org.hibernate.engine.SessionImplementor, org.hibernate.engine.QueryParameters, boolean) line: 661	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.Loader).doQueryAndInitializeNonLazyCollections(org.hibernate.engine.SessionImplementor, org.hibernate.engine.QueryParameters, boolean) line: 224	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.Loader).loadEntity(org.hibernate.engine.SessionImplementor, java.lang.Object, org.hibernate.type.Type, java.lang.Object, java.lang.String, java.io.Serializable, org.hibernate.persister.entity.EntityPersister) line: 1785	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.entity.AbstractEntityLoader).load(org.hibernate.engine.SessionImplementor, java.lang.Object, java.lang.Object, java.io.Serializable) line: 47	
org.hibernate.loader.entity.EntityLoader(org.hibernate.loader.entity.AbstractEntityLoader).load(java.io.Serializable, java.lang.Object, org.hibernate.engine.SessionImplementor) line: 41	
org.hibernate.persister.entity.JoinedSubclassEntityPersister(org.hibernate.persister.entity.AbstractEntityPersister).load(java.io.Serializable, java.lang.Object, org.hibernate.LockMode, org.hibernate.engine.SessionImplementor) line: 2730	
org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(org.hibernate.event.LoadEvent, org.hibernate.persister.entity.EntityPersister, org.hibernate.engine.EntityKey, org.hibernate.event.LoadEventListener$LoadType) line: 365	
org.hibernate.event.def.DefaultLoadEventListener.doLoad(org.hibernate.event.LoadEvent, org.hibernate.persister.entity.EntityPersister, org.hibernate.engine.EntityKey, org.hibernate.event.LoadEventListener$LoadType) line: 346	
org.hibernate.event.def.DefaultLoadEventListener.load(org.hibernate.event.LoadEvent, org.hibernate.persister.entity.EntityPersister, org.hibernate.engine.EntityKey, org.hibernate.event.LoadEventListener$LoadType) line: 123	
org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(org.hibernate.event.LoadEvent, org.hibernate.persister.entity.EntityPersister, org.hibernate.engine.EntityKey, org.hibernate.event.LoadEventListener$LoadType) line: 177	
org.hibernate.event.def.DefaultLoadEventListener.onLoad(org.hibernate.event.LoadEvent, org.hibernate.event.LoadEventListener$LoadType) line: 87	
org.hibernate.impl.SessionImpl.fireLoad(org.hibernate.event.LoadEvent, org.hibernate.event.LoadEventListener$LoadType) line: 862	
org.hibernate.impl.SessionImpl.get(java.lang.String, java.io.Serializable) line: 799	
org.hibernate.impl.SessionImpl.get(java.lang.Class, java.io.Serializable) line: 792	
net.bioclipse.lis.genericDAO.GenericDAO<T>.getById(long) line: 37	
sun.reflect.NativeMethodAccessorImpl.invoke0(java.lang.reflect.Method, java.lang.Object, java.lang.Object[]) line: not available [native method]	
sun.reflect.NativeMethodAccessorImpl.invoke(java.lang.Object, java.lang.Object[]) line: not available	
sun.reflect.DelegatingMethodAccessorImpl.invoke(java.lang.Object, java.lang.Object[]) line: not available	
java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object...) line: not available	
org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(java.lang.Object, java.lang.reflect.Method, java.lang.Object[]) line: 287	
org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint() line: 181	
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed() line: 148	
net.bioclipse.lis.genericDAO.FinderIntroductionInterceptor.invoke(org.aopalliance.intercept.MethodInvocation) line: 18	
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed() line: 170	
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[]) line: 176	
$Proxy24.getById(long) line: not available	
net.bioclipse.lis.business.project.ProjectManager.getExperiment(long) line: 67	
sun.reflect.NativeMethodAccessorImpl.invoke0(java.lang.reflect.Method, java.lang.Object, java.lang.Object[]) line: not available [native method]	
sun.reflect.NativeMethodAccessorImpl.invoke(java.lang.Object, java.lang.Object[]) line: not available	
sun.reflect.DelegatingMethodAccessorImpl.invoke(java.lang.Object, java.lang.Object[]) line: not available	
java.lang.reflect.Method.invoke(java.lang.Object, java.lang.Object...) line: not available	
org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(java.lang.Object, java.lang.reflect.Method, java.lang.Object[]) line: 287	
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[]) line: 165	
$Proxy25.getExperiment(long) line: not available	
lis_gui.setup.explorer.model.folders.Experiment.refresh() line: 28	
lis_gui.setup.explorer.ExplorerContentProvider.treeModelUpdated(lis_gui.setup.explorer.model.TreeEvent) line: 107	
lis_gui.setup.explorer.model.treeLeafs.Plate(lis_gui.setup.explorer.model.Model).fireUpdate() line: 8	
lis_gui.setup.explorer.View$2$1.run() line: 135

I am not sure what it is waiting for. I am trying to reload my persistant objects from a thread which is started from the gui. It works perfectly when done from the main thread but not from my other thread. Do anybody have an idea or hint at what might be wrong?

[karldmoore]

It looks like the code is deadlocked in the connection pool when trying to borrow a connection. I would presume all the connections are already allocated and it can't create anymore. It's therefore going to wait until a connection is freed up.

[Jonathan Alvarsson]

It looks like the code is deadlocked in the connection pool when trying to borrow a connection. I would presume all the connections are already allocated and it can't create anymore. It's therefore going to wait until a connection is freed up.

But that won't ever happend as far as I can see. What can I do?

[karldmoore]

But that won't ever happend as far as I can see. What can I do?

I don't understand how this can't ever happen, it seems to be. If you leave it on the main thread, then it's going to use the same thread bound connection. As you push it onto another thread, it's going to try and get a new thread bound connection.

[Jonathan Alvarsson]

I don't understand how this can't ever happen, it seems to be. If you leave it on the main thread, then it's going to use the same thread bound connection. As you push it onto another thread, it's going to try and get a new thread bound connection.

Okey I agree with what you say but I don't understand why this implies that it will get a free connection sometime. When my thread deadlocks it is the only thread actually running. The main thread is only waiting for new input from the user by the gui. So the main thread is certainly not gonna be putting any connections back in the pool...

Do anyone know how many connections the pool contains? (It seems to me like there aren't enough) I guess some are tied up for Hibernate lazy loading and this means I probably would like to have more of them?

Another question that arise is: do I have to do something special when a thread ends like closing a session in special way for the connections to be returned?

[karldmoore]

Okey I agree with what you say but I don't understand why this implies that it will get a free connection sometime. When my thread deadlocks it is the only thread actually running. The main thread is only waiting for new input from the user by the gui. So the main thread is certainly not gonna be putting any connections back in the pool...

I can't see any transaction support in the stracktrace. I might make sense to make one of your beans transactional e.g. ProjectManager. Are you using a release mode in the Hibernate configuration?
http://www.springframework.org/docs/...ansaction.html

Do anyone know how many connections the pool contains? (It seems to me like there aren't enough) I guess some are tied up for Hibernate lazy loading and this means I probably would like to have more of them?

The number of connections will be defined in the configuration. If you aren't setting this yourself, the JavaDoc might give you the default.

Another question that arise is: do I have to do something special when a thread ends like closing a session in special way for the connections to be returned?

If you are letting Spring manage transactions and connections there shouldn't be anything to worry about.

[Jonathan Alvarsson]

I can't see any transaction support in the stracktrace. I might make sense to make one of your beans transactional e.g. ProjectManager. Are you using a release mode in the Hibernate configuration?
http://www.springframework.org/docs/...ansaction.html

Most of my methods are configured as transactions. This one is not because it is a getter that loads objects from the database and in order to get the lazy loading to work the sessions needs to be open and I have not succeded in having transactional methods session kept open for lazy loading after the method that loads i finished. I don't think I have defined a release mode but my datasource been looks like this:

<bean 
    id="dataSource"
    class="org.apache.commons.dbcp.BasicDataSource"
    destroy-method="close"> ...

Will the destroy-method="close" do something like setting the release mode?

The number of connections will be defined in the configuration. If you aren't setting this yourself, the JavaDoc might give you the default.

I figured out how to set the number of connections and I also figured out that each of my object loading ties up one session for the lazy loading to work. And when I have used up all connections my thread deadlocks waiting for more.

How is this to be done? I need the lazy loading but I can't afford to have one database connection for each time I load something from the database...

I guess what I need is for the session to grab a connection from the pool when it needs one and put it back when it is not using it... or how is this problem normally solved?

[karldmoore]

Most of my methods are configured as transactions. This one is not because it is a getter that loads objects from the database and in order to get the lazy loading to work the sessions needs to be open and I have not succeded in having transactional methods session kept open for lazy loading after the method that loads i finished. I don't think I have defined a release mode.

I'm not quite sure this is going to work. I'm not sure you want to share Hibernate Session between threads as it isn't thead-safe. The release mode I was refering to is here.
http://www.hibernate.org/hib_docs/v3...ection-release

I figured out how to set the number of connections and I also figured out that each of my object loading ties up one session for the lazy loading to work. And when I have used up all connections my thread deadlocks waiting for more.

How is this to be done? I need the lazy loading but I can't afford to have one database connection for each time I load something from the database...

I guess what I need is for the session to grab a connection from the pool when it needs one and put it back when it is not using it... or how is this problem normally solved?

This all just doesn't sound right. I'd have to play and a look into this more to understand what's going on.

[Jonathan Alvarsson]

See also this post it is somewhat related to the same problem...