[rules-users] Timers and fireAllRules

Tue Jul 2 13:00:43 EDT 2013

I'm grateful for the clarification that the timer behavior is changing in Drools 6.  I was planning on exploiting the Drools 5 behavior to fire certain rules asynchronously at intervals using a timer, even when the engine was otherwise idle.  I don't want to use fireUntilHalt because I need to make numerous updates to facts in a batch in Java code, and I don't want any rules to fire prematurely.  To prepare for Drools 6, then, it looks like I should use Java to implement the timer, update the working memory, and call fireAllRules.  I'd prefer to be able to specify this declaratively in the DRL file as I can now in Drools 5, but since I want to future-proof my code I'll need a different approach.

Best wishes,
Tom

From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Wolfgang Laun
Sent: Monday, June 24, 2013 4:02 PM
To: Rules Users List
Subject: Re: [rules-users] Timers and fireAllRules

You just make sure that the documentation for 5.x remains as I've added it, and that it is updated accordingly for the 6.x Expert manual.
I don't think that the behaviour in 5.x when fireAllRules() is called and repeating timers execute their tasks even when the Engine is idle is evil. The general flow of logic is consistent even though some executions happen later compared to what would happen when running in fireUntilHalt.
But you can indeed uphold the position that any timer activity is in conflict with the Engine being suspended after fireAllRules() returns. But what should be the consequence? Delay the return? Terminate the timers? Disallow timers being launched in a run initiated by fireAllRules()? Let's hope that 6.x reacts cleanly...
-W

On 24 June 2013 21:05, Mark Proctor <mproctor at codehaus.org<mailto:mproctor at codehaus.org>> wrote:
btw sorry about the confusion. The reason was we have changed the behaviour in 6, and in the mean time I'd forgotten what the exact behaviour was in 5.

In 6.x there is no async behaviour, for fireAllRules,  all action happens in the user thread.  So there will be no rule firing if fireAllRules (passive mode) is not called, or you are not using fireUntilHalt (reactive mode).

There have been several discussion on IRC, and the conclusion was were very uncomfortable with async operations of timers, in passive mode. If people want reactive behaviour, they should use the engine in reactive mode, if they want passive behaviour, they should use the engine in passive mode.

Timers  are no longer part of  Agenda, and instead we have a TimerNode that lives in the network. It's role is simply to control tuple propagation. The code is a lot simpler and more isolated than 5.x, this is also very helpful (if not necessary) in the multi-core work we plan to do.
https://github.com/droolsjbpm/drools/blob/master/drools-core/src/main/java/org/drools/core/phreak/PhreakTimerNode.java

We do think there may be some future use cases for a mixed hybrid/passive execution mode. Where some rules are passive, some reactive, but we'd rather that we found a way to do this declaratively.

Mark

On 22 Jun 2013, at 07:17, Wolfgang Laun <wolfgang.laun at gmail.com<mailto:wolfgang.laun at gmail.com>> wrote:

Added to Chapter-LanguageReference<https://github.com/droolsjbpm/drools/tree/master/drools-docs/drools-expert-docs/src/main/docbook/en-US/Chapter-LanguageReference> / Section-Rule.xml on master.
-W

On 20 June 2013 22:55, Wolfgang Laun <wolfgang.laun at gmail.com<mailto:wolfgang.laun at gmail.com>> wrote:
OK, and now? You can wrap it into a couple of docbook tags and add it to the Expert manual, I'm not reserving the copyright ;-)
-W

On 20 June 2013 21:29, Mark Proctor <mproctor at codehaus.org<mailto:mproctor at codehaus.org>> wrote:
I assumed you were quoting from some documentation.
Mark

On 20 Jun 2013, at 17:08, Wolfgang Laun <wolfgang.laun at gmail.com<mailto:wolfgang.laun at gmail.com>> wrote:

You sound absolutely sibyllic. Which documentation will you update - I'm not aware of any documentation describing the behaviour of timers. What, in your opinion, was the "behaviour in an older version"? And what "older version" are you referring to anyway? I've ascertained that what I described is the behaviour in 5.1.1, 5.2.0, 5.3.0, 5.4.0 and 5.5.0.
And: where is it written that execution tied to a repeating timer "must be constrained within fireAllRules?" I could make a very good case for arguing that RHS executions due to timer expiry aren't "firing" in the classic sense - that's just what happens when the LHS matches.
-W

On 20 June 2013 15:44, Mark Proctor <mproctor at codehaus.org<mailto:mproctor at codehaus.org>> wrote:
We'll update the documentation, that was probably the behaviour in an older version. The behaviour should not have rules async firing, unless there is proper async controls, as with fireUntilHalt, otherwise the firings must be constrained within fireAllRules.

Mark
On 20 Jun 2013, at 12:04, Wolfgang Laun <wolfgang.laun at gmail.com<mailto:wolfgang.laun at gmail.com>> wrote:

>    A rule controlled by a timer becomes active when it matches, and
>    once for each individual match. Its consequence is executed
>    repeatedly, according to the timer's settings. This stops as soon
>    as the condition doesn't match any more.
>
>    Consequences are executed even after control returns from a call
>    to fireUntilHalt(). Moreover, the Engine remains reactive to any
>    changes made to the Working Memory. For instance, removing a fact
>    that was involved in triggering the timer rule's execution causes
>    the repeated execution to terminate, or inserting a fact so that
>    some rule matches will cause that rule to fire. But the Engine is
>    not continually active, only after a rule fires, for whatever
>    reason. Thus, reactions to an insertion done asynchronously will
>    not happen until the next execution of a timer-controlled rule.
>
>    Disposing a session puts an end to all timer activity.
>
>    -W
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