On Thu, Sep 29, 2011 at 8:13 AM, Carsten Ziegeler <cziege...@apache.org> wrote: > 2011/9/29 Bertrand Delacretaz <bdelacre...@apache.org>: >> On Thu, Sep 29, 2011 at 3:16 PM, Carsten Ziegeler <cziege...@apache.org> >> wrote: >>> I wouldn't rely on concurrent reads with the same session. In rare >>> cases this can lead to problems! >> >> Do you have more info about that? >> (not disputing, just curious) > > Not that much :) But with heavy concurrent reads I ran into a problem > from time to time and I asked the Jackrabbit developers about it. And > they confirmed that this "might happen" and they discourage all > concurrent usage. This was roughly eight months ago
FWIW, I think the bigger point is that concurrent usage of a session isn't a supported use case. It *might* work some of the time, but if it doesn't, you shouldn't be surprised. Regards, Justin > > > Regards > Carsten > >> >> -Bertrand >> >> >>> 2011/9/29 Bertrand Delacretaz <bdelacre...@apache.org>: >>>> Hi, >>>> >>>> On Thu, Sep 29, 2011 at 2:09 PM, Markus Joschko >>>> <markus.josc...@gmail.com> 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 >>>> >>> >>> >>> >>> -- >>> Carsten Ziegeler >>> cziege...@apache.org >>> >> > > > > -- > Carsten Ziegeler > cziege...@apache.org >
