Problem with JTA/JTS

Hi,

I've run in to some troubles using PostgreSQL 7.2 and JTA/JTS. We are
developing a J2EE application using JBossTx as JTA implementation. The
problem occurs when lots of small transactions are created and executed
sequentially. Below is a code snippet that simulates JTA interaction
with the PostgreSQL data source adapter and triggers the error.

--- begin code snippet ---

org.postgresql.PostgresqlDataSource xaDs =
new org.postgresql.PostgresqlDataSource();
xaDs.setUser( "<user>" );
xaDs.setPassword( "<pwd>" );
xaDs.setDatabaseName( "<dbname>" );
xaDs.setServerName( "<host>" );

javax.sql.XAConnection xaCon = xaDs.getXAConnection();
for ( int i = 0; i < 999; i++ )
{
javax.transaction.xa.XAResource xaRs = xaCon.getXAResource();
// some xid implementation (org.jboss.tm.XidImpl)
javax.transaction.xa.Xid xid = new SomeXidImpl();
xaRs.start( xid, javax.transaction.xa.XAResource.TMNOFLAGS );

Connection conn = xaDs.getXAConnection().getConnection();
Statement stmnt = conn.createStatement();
stmnt.executeUpdate( "INSERT INTO some_table (some_value) " +
"VALUES (" + i + ");" );
conn.close();

xaRs.end( xid, javax.transaction.xa.XAResource.TMSUCCESS );
xaRs.commit( xid, true );

// if sleep time is removed we get exception after some iterations
Thread.currentThread().sleep( 1000 );
}

--- end code snippet ---

Removing the sleep will result in following exception after some
iterations:

--- begin stack trace ---

Exception in thread "main" Something unusual has occured to cause the
driver to fail. Please report this exception:
Exception: java.sql.SQLException: FATAL 1: Sorry, too many clients
already

Stack Trace:

java.sql.SQLException: FATAL 1: Sorry, too many clients already

at org.postgresql.Connection.openConnection(Connection.java:274)
at org.postgresql.Driver.connect(Driver.java:149)
at
org.postgresql.PostgresqlDataSource.getConnection(PostgresqlDataSource.java:266)
at
org.postgresql.PostgresqlDataSource.getConnection(PostgresqlDataSource.java:203)
at
org.postgresql.xa.XADataSourceImpl.newConnection(XADataSourceImpl.java:293)
at
org.postgresql.xa.XAConnectionImpl.getUnderlying(XAConnectionImpl.java:946)
at
org.postgresql.xa.ClientConnection.getUnderlying(ClientConnection.java:554)
at
org.postgresql.xa.ClientConnection.createStatement(ClientConnection.java:121)
at Test.main(Test.java:147)
End of Stack Trace

at org.postgresql.Driver.connect(Driver.java:166)
at
org.postgresql.PostgresqlDataSource.getConnection(PostgresqlDataSource.java:266)
at
org.postgresql.PostgresqlDataSource.getConnection(PostgresqlDataSource.java:203)
at
org.postgresql.xa.XADataSourceImpl.newConnection(XADataSourceImpl.java:293)
at
org.postgresql.xa.XAConnectionImpl.getUnderlying(XAConnectionImpl.java:946)
at
org.postgresql.xa.ClientConnection.getUnderlying(ClientConnection.java:554)
at
org.postgresql.xa.ClientConnection.createStatement(ClientConnection.java:121)
at Test.main(Test.java:147)

--- end stack trace ---

The PostgreSQL console prints a lot of "DEBUG: pq_recvbuf: unexpected
EOF on client connection" and one "FATAL 1: Sorry, too many clients
already" causing the exception on our side.

It works with a delay after each completed transaction, but we cannot
have such a delay since it will decrease performance too much. Any ideas
why a delay is needed? Almost as if the db server or the java stuff
needs some time to make sure the connection is closed/free and there is
no need to create a new one.

Using java.sql.DriverManager getting a connection works fine but we need
the J2EE stuff.

Best regards,

Johan Svensson [johan(dot)svensson(at)windh(dot)net]
Kernel Developer, .windh AB