Question about concurrent modifications

Goonie · **Posted:** Thu Oct 14, 2004 3:17 pm

Hello everyone,

Hibernate version: Hibernate 2.1.3
Name and version of the database you are using: MySQL 4.0

In my web-application, I today observed the event of two concurrent requests modifying the same persistant object (but different properties/columns) at neary the same time. The result was that the "second" request has undone the changes of the "first".

This is no wonder, since I configured the 2nd level cache to use the "nonstrict-read-write" strategy.

My question is if the only thing I have to do to prevent this error in the future is to switch to "read-write" strategy?

I am using MySQL 4.0 and the table in question is using MyISAM.
The 2nd level cache is an EHCache 0.7.
I have set "hibernate.connection.isolation" to 4.
My application uses the Open Session in View pattern (with the Spring filter).
My application is not clustered.

Regards,

Andreas

christian · **Posted:** Thu Oct 14, 2004 3:19 pm

Thats most likely not a caching problem (though you should know what it does before enabling some random concurrency strategy), but a problem tha can be solved using optimistic locking and automatic versioning. Check the documentation.

Goonie · **Posted:** Fri Oct 15, 2004 4:04 am

Since my application does not use any "long transactions", does the use of automatic versioning make any sense here?

Maybe I would just need to load my persistant object with FOR UPDATE (LockMode.UPGRADE) in my updating methods.

The methods in question look like this:

Code:

public void setName(int catId)
{
Cat cat = Session.load(Cat.class, catId);
cat.setName(...);
}
public void setSex(int catId)
{
Cat cat = Session.load(Cat.class, catId);
cat.setSex(...);
}

The problem I described in the original post was caused by one thread calling setName and the other calling setSex at the same time.

Is it advisable to use LockMode.UPGRADE in these situations?

Would LockMode.UPGRADE have any effect if I continue to use MySQL 4.0 and MyISAM tables?

Regards,

Andreas