Problems with threads modifying properties

[Delia Fernandez <df...@fidesol.org>]

I'm new to Jackrabbit and have a couple of questions about threading over the
same Repository:

- While reading jsr-170 specification (as introduction to Jackrabbit) I
found this paragraph explaining thread-safety requirements:
 "A content repository implementation is not required to provide thread-safe
implementations of other interfaces. As a consequence, an application which
concurrently or sequentially operates against objects having affinity to a
particular Session through more than one thread must provide synchronization
sufficient to ensure no more than one thread concurrently operates against
that Session and changes made by one thread are visible to other threads." 

I tried to test it with several threads sharing the same code. If each one
of the threads logs on a different session and includes synchronization
parameters as follows:

[...]
synchronized(this){
     Session session=repository.login(new
SimpleCredentials("user","pass".toCharArray());
     Node node=session.getRootNode.getNode("node_to_modify");
     node.setProperty("jcr:data","new data");
     session.save();
     session.logout();
}
[...]

The first thread achieves to modify the property successfully, while the
others just get the following error:

0186c41e-7d73-4b5a-9e45-3990cc7c5597/{http://www.jcp.org/jcr/1.0}data has
been modified externally

How could I modify the values over the same node without errors?
and, if the answer to the previous question is "locking the node", what's
the correct sequence to do it?


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Re: Problems with threads modifying properties

[David Nuescheler <da...@gmail.com>]

hi delia,

from the code snippet you submitted i can only assume that "this" is probably
the thread you are running in.

if that's the case then synchronizing on (this) doesn't do much, a quick
fix for your testcode could be something like synchronized(this.getClass()).

anyway, the statement you quoted from the specification is with
respect to sharing
a session between multiple threads which is something that you are not even
attempting to do as far as i can tell.

regards,
david

On 4/26/07, Delia Fernandez <df...@fidesol.org> wrote:
>
> I'm new to Jackrabbit and have a couple of questions about threading over the
> same Repository:
>
> - While reading jsr-170 specification (as introduction to Jackrabbit) I
> found this paragraph explaining thread-safety requirements:
>  "A content repository implementation is not required to provide thread-safe
> implementations of other interfaces. As a consequence, an application which
> concurrently or sequentially operates against objects having affinity to a
> particular Session through more than one thread must provide synchronization
> sufficient to ensure no more than one thread concurrently operates against
> that Session and changes made by one thread are visible to other threads."
>
> I tried to test it with several threads sharing the same code. If each one
> of the threads logs on a different session and includes synchronization
> parameters as follows:
>
> [...]
> synchronized(this){
>      Session session=repository.login(new
> SimpleCredentials("user","pass".toCharArray());
>      Node node=session.getRootNode.getNode("node_to_modify");
>      node.setProperty("jcr:data","new data");
>      session.save();
>      session.logout();
> }
> [...]
>
> The first thread achieves to modify the property successfully, while the
> others just get the following error:
>
> 0186c41e-7d73-4b5a-9e45-3990cc7c5597/{http://www.jcp.org/jcr/1.0}data has
> been modified externally
>
> How could I modify the values over the same node without errors?
> and, if the answer to the previous question is "locking the node", what's
> the correct sequence to do it?
>
>
> --
> View this message in context: http://www.nabble.com/Problems-with-threads-modifying-properties-tf3650545.html#a10197087
> Sent from the Jackrabbit - Users mailing list archive at Nabble.com.
>
>