[rules-users] Drools Flow :Persistence Problem : Restore StatefulKnowledgeSession from database

[Vijay K Pandey]

Is session (StatefulKnowledgeSession) thread safe?

-----Original Message-----
From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Kris Verlaenen
Sent: Tuesday, November 17, 2009 4:48 AM
To: Rules Users List; Vijay K Pandey
Cc: Pardeep.Ruhil at lntinfotech.com
Subject: Re: [rules-users] Drools Flow :Persistence Problem : Restore StatefulKnowledgeSession from database

Preferably you should cache the session itself as well (so you don't
have to recreate it all the time) and reuse that across you application.
  Or you could have multiple independent sessions as well.  If you store
the key of the session somewhere, you can easily restore this session
(or sessions) after failure.

Kris

Quoting Vijay K Pandey <VPandey at mdes.ms.gov>:

> Let's say where we don't need timers - in those cases one can create
> (create only if its not there) a global session (create the
> sessioninfo at the drools startup - store the session primary key
> somewhere) - reuse this session across everywhere?
>
> Vijay
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Kris
> Verlaenen
> Sent: Monday, November 16, 2009 5:12 PM
> To: Rules Users List; Pardeep.Ruhil at lntinfotech.com
> Subject: Re: [rules-users] Drools Flow :Persistence Problem : Restore
> StatefulKnowledgeSession from database
>
> Pardeep,
>
> The behavior you are describing is indeed correct.  The session in
> this
> case is a global session, meaning that it will be used for all
> process
> instances.  Note however that, unless you are using timers, all
> other
> state (process instance state, work items, etc.) is persisted
> separately
> and the session state will basically be empty.
>
> It is also possible to have one session per process instance (or
> whatever partitioning you like).  A session has a unique id (which
> you
> can specify when reloading the session).  You'll then have to load
> the
> right session before continuing the execution of your process
> instance.
>
> Kris
>
> Quoting Pardeep.Ruhil at lntinfotech.com:
>
> > Hi Salaboy,
> > Thanks for you replying.
> > Yes, of course it is storing multiple process instance Id in the
> > database.
> > But, what I feel is that it will fail when I am trying to run two
> > workflow
> > at the same time simultaneously, using the same code by
> dynamically
> > providing the workflow name and the parameters for each of them.
> > Ideally there should be two entries for the
> StatfulKnowledgeSession
> > object
> > because when I try to load the StatefulKnowledgeSession object
> from
> > the
> > database it will give me the session object of the workflow which
> is
> > last
> > executed.
> >
> > For example lets  suppose I have two workflow 1 and 2 having two
> > humantask
> > in each of them . So when I finish the first Human Task of both
> > workflow
> > one by one.  SessionInfo  present in the database is of workflow 2
> > (if 2
> > is executed last). Because there is no field in the sessioninfo
> > entity of
> > the database regarding to which workflow it belongs to. Am I right
> ?
> > So when I  try to finish the 1st workflow by executing the 2nd
> > humantask
> > left in it , I need to reload the StatfulKnowledgeSession object
> from
> > the
> > database. As there is no way of distinguishing that the session
> > object
> > store in the database is of which workflow , there might be a
> problem
> > as I
> > may get the ksession object of 2nd workflow.
> >
> > In case of Process Instance it is fine , because there is a field
> > 'processId' which will distinguish which processInstanceId belongs
> to
> >
> > which worklowId or processId.
> > But in case of Session , there is noting as such.
> > I don't what I am saying is handled in drools persistence. Please
> let
> > me
> > know if it there or not.
> >
> > Thanks & Regards
> >
> > Pardeep Ruhil
> >
> >
> >
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