Re: [ODMG] lock progagation flag?

[Phil Warrick <wa...@bmed.mcgill.ca>]

Hi Thomas,

>> I could submit the changes on the latest cvs head for your perusal if 
>> you like.
> 
> 
> Just post your stuff, I'll review it and check it in!

I found that adding a flag to the collection descriptor and reference 
descriptor wasn't quite the right approach.  As I construct a new graph, 
I must query my large graph (the one that doesn't change much and 
shouldn't propagate locks), and so a read lock is obtained on one of 
these objects which gave me the large delay that I must avoid 
(ImplicitLocking=true).  So I added a flag "acceptLocks" (default=true) 
to the class descriptor itself which is checked in 
org.apache.ojb.odmg.TransactionImpl.lock(...) (see below).

It's maybe a little cleaner this way: only the targetted class needs to 
be labelled, not all references to it.

Affected files:

repository.dtd
repository_user.xml
org.apache.ojb.broker.metadata.RepositoryTags
org.apache.ojb.broker.metadata.RepositoryElements
org.apache.ojb.broker.metadata.ClassDescriptor
org.apache.ojb.broker.metadata.RepositoryXmlHandler
org.apache.ojb.odmg.TransactionImpl

Hope this is helpful.

Phil

  <class-descriptor
    	  class="A"
    	  table="A_TABLE"
    	  accept-locks="false"
    >

    public void lock(Object obj, int lockMode) throws 
LockNotGrantedException
{
         ClassDescriptor cld = 
this.getBroker().getClassDescriptor(obj.getClass());
         if (!cld.isAcceptLocks())
         {
		if (log.isDebugEnabled())
                 	log.debug("skipping lock on class: " + 
cld.getClassNameOfObject() + " object " + obj.toString());
             return;
         }
         else
         {
             if (log.isDebugEnabled())
                 log.debug("proceeding with lock on class: " + 
cld.getClassNameOfObject() + " object " + obj.toString());
         }
	...
}	

[IMPORTANT]Re: [ODMG] lock progagation flag?

["J. Russell Smyth" <dr...@cox.net>]

It needs to be noted that as of this change, anyone expecting the
old/default behavior (ie accept-locks="true") will need to make sure
they are using the latest repository.dtd, as this is where the default 
lives - without it everything acts as accept-locks="false" and
persisting new instances with Transaction.lock() will not persist
anything. I just spent about 8 hours trying to figure out why my code
suddenly failed....

I hate to complain, 'cause everyone here works hard to create a good
product and is very helpful, but It would be helpful if "breaking"
changes that require user intervention (ie copying dtds) were
"announced" to the list to prevent just this kind of problem.

Re: [ODMG] lock progagation flag?

[Thomas Mahler <th...@apache.org>]

Hi Phil,

Phil Warrick wrote:
<snip>

> I found that adding a flag to the collection descriptor and reference 
> descriptor wasn't quite the right approach.  As I construct a new graph, 
> I must query my large graph (the one that doesn't change much and 
> shouldn't propagate locks), and so a read lock is obtained on one of 
> these objects which gave me the large delay that I must avoid 
> (ImplicitLocking=true).  So I added a flag "acceptLocks" (default=true) 
> to the class descriptor itself which is checked in 
> org.apache.ojb.odmg.TransactionImpl.lock(...) (see below).
> 
> It's maybe a little cleaner this way: only the targetted class needs to 
> be labelled, not all references to it.
> 

Well done! The solution looks really elegant this way!
I just checked it into CVS.

Thanks,
Thomas


> Affected files:
> 
> repository.dtd
> repository_user.xml
> org.apache.ojb.broker.metadata.RepositoryTags
> org.apache.ojb.broker.metadata.RepositoryElements
> org.apache.ojb.broker.metadata.ClassDescriptor
> org.apache.ojb.broker.metadata.RepositoryXmlHandler
> org.apache.ojb.odmg.TransactionImpl
> 
> Hope this is helpful.
> 
> Phil
> 
>  <class-descriptor
>          class="A"
>          table="A_TABLE"
>          accept-locks="false"
>    >
> 
>    public void lock(Object obj, int lockMode) throws 
> LockNotGrantedException
> {
>         ClassDescriptor cld = 
> this.getBroker().getClassDescriptor(obj.getClass());
>         if (!cld.isAcceptLocks())
>         {
>         if (log.isDebugEnabled())
>                     log.debug("skipping lock on class: " + 
> cld.getClassNameOfObject() + " object " + obj.toString());
>             return;
>         }
>         else
>         {
>             if (log.isDebugEnabled())
>                 log.debug("proceeding with lock on class: " + 
> cld.getClassNameOfObject() + " object " + obj.toString());
>         }
>     ...
> }   
> 
> 
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