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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