And one more question: how is Transaction.DbLocked defined ?
Werner
On Thu, 3 Jun 2004 01:18:40 +0530, [EMAIL PROTECTED] wrote:
>
>Werner,
>
> Below the code you asked for.
>
>I'm still very concerned about this:
>Q. Transaction1 in thread1 has DBLocked a row in a table. Now will
>Transaction2 in thread2 be able to read the same row while transaction1
>is not commited ?
>
>=============================
>
>public Rocket retrieveByName(
> String name, Transaction tran, short accessMode)
> throws DbPersistenceException
> {
> Rocket rocket = null;
> OQLQuery aQuery = null;
> CastorTransaction cTran = null;
> Database db = null;
>
> try
> {
> cTran = (CastorTransaction) tran;
> db = cTran.getDatabase();
> aQuery =
> db.getOQLQuery(
> " SELECT rocket FROM rnd.domain.Rocket rocket "
> + " WHERE rocket.rocketName = $1");
> aQuery.bind(name);
>
> ArrayList list = retrieve(aQuery, accessMode);
>
> if ((list != null) && (list.size() > 0))
> {
> rocket = (Rocket) list.get(0);
> }
> }
> catch (PersistenceException ex)
> {
> daoErrorHandler(ex);
> }
>
> return rocket;
> }
>
>Jimmy
>
>-----Original Message-----
>From: Werner Guttmann [mailto:[EMAIL PROTECTED]
>Sent: Thursday, June 03, 2004 12:12 AM
>To: [EMAIL PROTECTED]
>Subject: Re: [castor-user] Dblocked mode & Mysql DB
>
>
>Jimmy,
>
>just browsing through your code, and the following code snipped caught
>my attention:
>
>Rocket rocket = rocket_DAO.retrieveByName (PRITHVI, transaction,
>Transaction.DbLocked);
>
>Can you please provide me with the details of what code is being
>executed as a result of the call to retrieveByName() ?
>
>Werner
>
>--Original Message Text---
>From: [EMAIL PROTECTED]
>Date: Wed, 2 Jun 2004 19:05:10 +0530
>
>
>
>Werner,
>
>
>
> Before we indulge into the time out issues, I would like
>your confirmation whether this is an expected behavior, wherein an
>object being
>dbLocked also gets the read lock on it.
>
>
>
>If the output of the sample code below is as the expected behavior, I
>wouldnt like to have read locks when I DbLock my object, since the
>performance
>of my application is degrading a lot.
>
>
>
> Regarding the table type, Im using innodb tables of mysql.
>
>
>
>
>Heres the Log of my test case:
>
>Setting data in DB
>
>Setting data in DB -- Done
>
>Starting Writer thread.....
>
>WriterThread -- Before db locking
>
>WriterThread -- After db locking
>
>WriterThread -- Before updating name
>
>ReaderThread -- Starting reader thread.....
>
>ReaderThread -- Trying to read.....
>
>WriterThread -- After updating name
>
>WriterThread -- Commiting & Closing transaction
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>ReaderThread -- Trying to read.....
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>ReaderThread -- Trying to read.....
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>ReaderThread -- Trying to read.....
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>ReaderThread -- Trying to read.....
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>WriterThread -- Clearing the DB
>
>ReaderThread -- Trying to read.....
>
>ReaderThread -- Read: [Rocket(WriterThread changed Name), with
>Fuel(Solid Ammonia)]
>
>WriterThread -- Clearing the DB... finished
>
>ReaderThread -- Stopped reading.
>
>
>
>The run method of Writer thread:
>
>
>
>public void run()
>
> {
>
> try
>
> {
>
> System.out.println("Starting Writer thread.....");
>
>
>
> System.out.println("WriterThread -- Before db locking");
>
>
>
> Rocket rocket =
>
> rocket_DAO.retrieveByName(
>
> PRITHVI, transaction, Transaction.DbLocked);
>
> System.out.println("WriterThread -- After db locking");
>
> System.out.println("WriterThread -- Before updating name");
>
>
> sleep(3000);
>
> rocket.setRocketName("WriterThread changed Name");
>
> System.out.println("WriterThread -- After updating name");
>
> sleep(10000);
>
> transaction.commitAndClose();
>
> System.out.println(
>
> "WriterThread -- Commiting & Closing transaction");
>
> sleep(5000);
>
> System.out.println("WriterThread -- Clearing the DB");
>
> deleteDB();
>
> System.out.println("WriterThread -- Clearing the DB...
>finished");
>
> }
>
> catch (Exception e)
>
> {
>
> e.printStackTrace();
>
> }
>
> }
>
>
>
>The run method of the Writer Thread:
>
>
>
> public void run()
>
> {
>
> try
>
> {
>
> System.out.println("ReaderThread -- Starting reader
>thread.....");
>
>
>
> while (read)
>
> {
>
> System.out.println("ReaderThread -- Trying to
>read.....");
>
>
>
> ArrayList rockets =
>
> rocket_DAO.retrieveAllRockets(txn,
>Transaction.ReadOnly);
>
> System.out.println("ReaderThread -- Read: " + rockets);
>
>
> sleep(1000);
>
> }
>
>
>
> System.out.println("ReaderThread -- Stopped reading.");
>
> }
>
> catch (Exception e)
>
> {
>
> e.printStackTrace();
>
> }
>
> }
>
>
>
>
>
>Thanks & Regards,
>
>Jimmy
>
>-----Original Message-----
>From: Werner Guttmann [mailto:[EMAIL PROTECTED]
>Sent: Wednesday, June 02, 2004 6:08 PM
>To: [EMAIL PROTECTED]
>Subject: Re: [castor-user] Dblocked mode & Mysql DB
>
>
>
>Jimmy,
>
>you could try increasing the lock timeout to a value that suits your
>needs via JDO.setLockTimeout (int) rather than messing around with read
>and write
>locks. Btw, what table type are you using with mySQL ?
>
>In addition, can you please provide us with a complete stack tarce of
>the exception being thrown when a read operation's lock expires ?
>
>Thanks
>Werner
>
>PleaseJDO.java--Original Message Text---
>From: [EMAIL PROTECTED]
>Date: Wed, 2 Jun 2004 17:02:33 +0530
>
>
>
>Hi,
>
>
>
>I working with Castor 0.9.5.3 (Cache type = NONE) & mySQL 4 and I am
>facing problems wherein castor says Read lock timeout, this usually
>occurs
>when I try to read an object in one thread, but at the same time some
>other thread has dblocked that object. I also happen to notice that,
>when I do a
>Dblock on an object, Castor applies both a read & write lock on the
>record, but mysql allows read on those records mapped to the object, at
>its prompt.
>
>
>
>I guess the read lock timeouts are happening because the object thats
>been dbLocked, is been held in the lock state for more than the timeout
>period
>and the reading thread is not allowed access to this object. But this
>could be serious limitation, since in my application there many threads
>working on
>the same object/table and if a thread happen to dblocked that object for
>some period of time, then the remaining threads who just want to read
>has to
>wait, till the read lock is released.
>
>
>
>So I would like to know is there any way that I could just do a write
>lock and not read lock on the object that I would like to update. Also
>does Castor
>have any specific way of retrieving objects referenced in an object; say
>in the order its been mapped in the mapping file or does Castor loads
>the object
>in an arbitrary fashion.
>
>
>
>
>
>Thanks & Regards,
>
>Jimmy Thomas
>
>
>
>
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