[Pljava-dev] stack depth limit exceeded (NOT from infinite recursion)

OK, I see the problem. The connection spawns a new thread, that thread
loads classes. And of course, the stack of that thread cannot be
compared to the stack of the caller thread. PostgresSQL (since it's
singlethreaded) thinks that you eat a vast amount of stack.

I'll address this on the PostgreSQL hackers mailing list and see if I
can convince them to install something that makes it possible to
temporary shut off the stack-check. A temporary work-around is to
reference the needed classes before making the connect call. That way,
the current thread will be the one who loads them.

Regards,
Thomas Hallgren

kstian wrote:

> Hi Thomas,
>
> Thanks for replying.
>
> I have gradually increased max_stack_depth in postgresql.conf to 16384
> (verified from show all in the db) but it did not seem to help.
>
> The following is the code I have for the trigger function. Basically,
> what I wanted it to do is, upon data update, I wanted to connect to
> serivcemix (jbi container) and publish the event to activeMQ. The
> problem happened on the line where I marked "==> <==". I also
> printed out the loaded classes from sqlj.Loader.java in findClass
> method and it showed a lot of loaded classes. These classes were to
> be passed to sql statement for loading.
>
> =================================
> mport java.sql.SQLException;
> import java.sql.ResultSet;
> import java.util.logging.Logger;
>
> import org.postgresql.pljava.TriggerData;
> import org.postgresql.pljava.TriggerException;
>
>
> import javax.jms.Connection;
> import javax.jms.JMSException;
> import javax.jms.Session;
> import javax.jms.MessageProducer;
>
> import org.activemq.ActiveMQConnectionFactory;
> import org.activemq.ActiveMQConnection;
> import org.activemq.message.ActiveMQTopic;
>
> public class Triggers {
>
> public static void afterUpdateTsr(TriggerData td) throws
> SQLException, JMSException
> {
> if (td.isFiredForStatement())
> throw new TriggerException(td, "Cannot process statement
> events.");
> if (td.isFiredBefore())
> throw new TriggerException(td, "Must be fired after event.");
> if (!td.isFiredByUpdate())
> throw new TriggerException(td, "Can only process UPDATE
> event");
> ResultSet _new = td.getNew();
> ResultSet _old = td.getOld();
> String[] args = td.getArguments();
> String status = args[1];
> if (args.length != 1)
> throw new TriggerException(td, "One argument is expected.");
> Logger log = Logger.getAnonymousLogger();
> log.info("After UPDATE to tservicerequest table with new
> tstatus = " + _new.getString(status) + ", old tstatus = " +
> _old.getString(status));
> ActiveMQConnectionFactory factory = new
> ActiveMQConnectionFactory(ActiveMQConnection.DEFAULT_USER,
> ActiveMQConnection.DEFAULT_PASSWORD,
> ActiveMQConnection.DEFAULT_BROKER_URL); //"tcp://localhost:61616");
> ActiveMQTopic pubTopic = new
> ActiveMQTopic("demo.org.servicemix.source");
> //ActiveMQTopic subTopic = new
> ActiveMQTopic("demo.org.servicemix.result");
> log.info("Connecting to JMS Server...");
> Connection connection = factory.createConnection();
> log.info("Before setClientID");
> ==>connection.start(); <==
> Session session = connection.createSession(false,
> Session.AUTO_ACKNOWLEDGE);
> MessageProducer producer = session.createProducer(pubTopic);
> //connection.start();
> log.info("Sending request to JMS Server...");
> producer.send(session.createTextMessage("New tstatus= " +
> _new.getString(status) + ", old tstatus= " + _old.getString(status)));
> log.info("Sent message: New tstatus= " +
> _new.getString(status) + ", old tstatus= " + _old.getString(status));
> //connection.close();
>
> }
> }
>
> ===============================================
>
> Thanks a lot for help.
>
> Regards,
> Kong
>
> Thomas Hallgren wrote:
>
>> kstian wrote:
>>
>>> Hi,
>>>
>>> I created the following Trigger and Function:
>>>
>>> ======================================
>>> CREATE FUNCTION afterUpdateTsr()
>>> RETURNS trigger
>>> AS 'pljava.Triggers.afterUpdateTservicerequest'
>>> LANGUAGE java;
>>>
>>> CREATE TRIGGER tsr_afterUpdate
>>> AFTER UPDATE ON tsr
>>> FOR EACH ROW
>>> EXECUTE PROCEDURE afterUpdateTsr(name);
>>> ==========================================
>>>
>>> Then in the afterUpdateTsr() java function, I was writing codes to
>>> connect to servicemix (a JBI container).
>>>
>>> In order to do that, I had to install 11 jar files in my postgresql
>>> table using sqlj.install_jar function.
>>>
>>> When the aferUpdateTsr() got triggered, it was throwing "stack depth
>>> limit exceeded" exception from native C. (I believed it's from
>>> ExecutionPlan.c). I also printed out the loaded classes from
>>> sqlj/Loader.java (findClass function) and found that pljava was
>>> loading a lot of classes.
>>> Was it the main reason causing this exception? How do I resolve
>>> this problem?
>>>
>> Normally, a "stack depth limit exceeded" exception is caused by a
>> function that calls SQL, that in turn calls a function that calls
>> SQL, etc. until you recurse so deep that the PostgreSQL callstack is
>> exhausted. If it's a controlled and expected recursion you can try to
>> increase the max_stack_depth variable in your postgresql.conf
>>
>> If you this doesn't help, then I'll have to know a bit more about
>> what your triggers are doing in order to assist you.
>>
>> Kind regards,
>> Thomas Hallgren
>>
>>
>>
>>
>>
>>
>