1:01 a.m.
Maciej Swiderski [https://community.jboss.org/people/swiderski.maciej] created the
discussion
"Re: Questions about knowledge session and memory resource issues"
To view the discussion, visit: https://community.jboss.org/message/734640#734640
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pmukundan wrote:
*Questions*
1. Does JBPM keep all process instance information in memory at all times ?
Process
instance is kept in session (working memory) one when it is active, meaning under
execution. Once done with the processing it is persisted into db.
pmukundan wrote:
*Questions*
2. Does JBPM keep all the knowledge base in memory at all times ?
Yes, knowledge
base is kept there all the time to secure all sessions will have access to all artifacts
stored in it.
pmukundan wrote:
3. For approach b to work, the internal handling of JBPM should enable me to load/unload
session at will. Does that work well? any firsthand experience ?
As far as I can tell it works well. If you keep session small you should get quite
good performance.
pmukundan wrote:
4. For approach b, if session dispose is called, do all process instances associated with
that session go dormant ? In other words, if a session dispose is executed, are the
process instances started by that session still in memory ?
Once the process
instance execution is completed (by completed I mean that it reached a safe point like
human task or catch events that makes process be in a sort of wait state) it is persisted
into db and will now longer be active/managed object. It still resides in memory as object
but it is disconnected from the session so it is safe to dispose the session.
pmukundan wrote:
5. My JVM crashes or needs to be restarted. Would all process instance information be
loaded into memory automatically or would that be done programatically ?
No, they
won't be, as mentioned earlier process instances are persisted in db and retrieved
only when requested. Just make sure you load knowledge base and session on startup and
register all work item handlers that are required.
NOTE: all my comments assume session persistence is used.
HTH
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1:36 a.m.
pmukundan [https://community.jboss.org/people/pmukundan] created the discussion
"Re: Questions about knowledge session and memory resource issues"
To view the discussion, visit: https://community.jboss.org/message/734953#734953
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Hi Maciej,
Thank you for your replay. It is very helpful. I have 1/2 followup question
Assumption : Session persistance is in use. JPA/hibenate mechanism is in use. The setup is
functioning.
*Scenario*
Whenever JBPM JVM gets a process launch request, I create a new Knowledge session. Use
that ksession to lauch the process instance. The process instance hits a human task node
and original launcher execution thread returns. That thread calls ksession dispose. Now
ksession is detached from process instance and task instance objects. All process instance
objects get saved into database through JPA.
*Questions :*
Does the ksession object get garbage collected immediately ?
Do the persisted task objects/process instance objects get
garbage collected ? Those are not required in memory until the user does something about
the task in a separate JVM.
*Background info*
I am trying to forecast the memory requirements for the JVM.
Memory contents of JVM at any time
1. Whole knowledge base
2. Active knowledge sessions( those not desposed at the moment)
3. Process instance and related objects ( This is what I want to get clarty on !!)
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1:44 a.m.
Maciej Swiderski [https://community.jboss.org/people/swiderski.maciej] created the
discussion
"Re: Questions about knowledge session and memory resource issues"
To view the discussion, visit: https://community.jboss.org/message/735281#735281
--------------------------------------------------------------
pmukundan wrote:
*Questions :*
Does the ksession object get garbage collected immediately ?
Do the persisted task objects/process instance objects get
garbage collected ? Those are not required in memory until the user does something about
the task in a separate JVM.
As soon as you dispose the session it will be eligible
to garbage collection, so I would say yes (with respect to the best practices for garbage
collection). Same apply to process and task instances, they will be cleaned up as soon as
there are no reference to them and since session is disposed that should be valid.
HTH
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