Hi,
On Thu, Sep 29, 2011 at 2:09 PM, Markus Joschko
<[email protected]> wrote:
I want to get some assumptions of mine clarified regarding the usage
of classes like Session and ResourceResolver in event handlers.
1. The jackrabbit session is not threadsafe
2. ResourceResolvers are not threadsafe
3. Event services (EventHandler, JobProcessor,
javax.jcr.observation.Eventlistener) can be called concurrently
All true AFAIK, ResourceResolvers are probably threadsafe by
themselves but use JCR sessions which are not.
Actually, reading from sessions from multiple threads is safe, it's
writing concurrently that's not ok.
-> Sessions and Resolvers should not be stored as instance members but
opened and closed in the in the process/handleEvent methods.
If you're reading only you can use a session concurrently.
If you're writing rarely you can synchronize on the session object
when writing for example.
If this is true, how expensive is the creation of a session? I read in
a blog, that the creation is considered expensive and wonder if it
makes more sense
to create the session new every time (and we have quite a lot of
events processed by the handlers), or to synchronize access to an
instance session?
Jackrabbit session creation is cheap, the idea is that you can create
a session on every HTTP request for example.
IMO synchronizing might cause more performance and latency issues as
creating new sessions as needed, but it depends on your usage patterns
I guess. I'd start with whatever feels right and measure response
times as needed.
-Bertrand
