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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