Re: Triggers?

    Hi Chad,

    As I mentioned earlier, we use a message queue based process.
We  wanted reliability as well as graceful shutdown and restart
capabilities.  The basic loop is based on a boolean that can be set
to false by either a  shutdown hook or a direct message to the queue
sent by a user or other program.  The app also understands several
other messages, such as the time to wait before reaccessing the
queue, so it allows for dynamic changes.

    In the processing loop, the app receives and processes messages
until the queue is empty, deleting each one after processing is completed.
Once no more messages are available, control returns to the main loop
where the app sleeps for a configurable number of milliseconds before
checking the queue again.

    While the app could run on any Java enabled platform ( and during
testing was run on a PC connecting to an AS/400 ), we knew it would
be run only on the '400 in production, so several performance
considerations for remote processing didn't enter the picture.  Also, in
this case, multiple threads would probably have caused unnecessary
complications as well as being slower overall.

    Although we prefer message queues, the basic concept can be
used with almost any implementation.  HTH,


                                                         Joe Sam

Joe Sam Shirah -        http://www.conceptgo.com
conceptGO         -        Consulting/Development/Outsourcing
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----- Original Message -----
From: "cornelius, chad" <chad.cornelius@xxxxxxxxxxxxxxxxxxxx>
To: "'Java Programming on and around the iSeries / AS400'"
<java400-l@xxxxxxxxxxxx>
Sent: Friday, January 21, 2005 2:13 PM
Subject: RE: Triggers?


> Thanks all for the input...  Do any of you have a sample program that
> listens to queue?  I have never written a listener before.  Any help is
> greatly appreciated.
>
> Thanks,
> Chad
>
>
> -----Original Message-----
> From: Ashish Kulkarni [mailto:kulkarni_ash1312@xxxxxxxxx]
> Sent: Friday, January 21, 2005 11:51 AM
> To: Java Programming on and around the iSeries / AS400
> Subject: Re: Triggers?
>
> Hi
> we have been doing this kind of stuff also, we need to
> create Purchase Order PDF files and email them to
> verndors, so RPG program write this info in a message
> queue, a java program is listening to this queue,(we
> have a seperate subsystem for running this java
> program)
> as soon as it get message, this listening program
> creates a thread which creates PDF file, emails it and
> then is killed.
> Ashish
> --- Joe Sam Shirah <jshirah@xxxxxxxxxxxxx> wrote:
>
> >
> >     Hi Chad,
> >
> >     Just to follow up on Chris' response:  Many
> > programmers think triggers
> > are a great idea until they do tons of work on each
> > DB change and things
> > begin to bog down.  You want to do the least amount
> > of work necessary when
> > you use a trigger, regerdless of language.
> >
> >     For example, one of our clients sends a fax when
> > certain criteria is met
> > for a database operation.  Rather than having the (
> > RPG ) trigger do the
> > time comsuming work, it just sends notification and
> > the required info to a
> > message queue, then returns.
> >
> >     A Java program monitors the message queue and
> > performs all necessary
> > operations asynchronously, so the original
> > application throughput is
> > affected as little as possible.
> >
> >
> >
> >     Joe Sam
> >
> > Joe Sam Shirah -        http://www.conceptgo.com
> > conceptGO         -
> > Consulting/Development/Outsourcing
> > Java Filter Forum:
> > http://www.ibm.com/developerworks/java/
> > Just the JDBC FAQs: http://www.jguru.com/faq/JDBC
> > Going International?
> > http://www.jguru.com/faq/I18N
> > Que Java400?
> > http://www.jguru.com/faq/Java400
> >
> >
> > ----- Original Message -----
> > From: <chris.delashmutt@xxxxxxxxxxxxx>
> > To: "Java Programming on and around the iSeries /
> > AS400"
> > <java400-l@xxxxxxxxxxxx>
> > Cc: <java400-l@xxxxxxxxxxxx>;
> > <java400-l-bounces@xxxxxxxxxxxx>
> > Sent: Friday, January 21, 2005 12:42 PM
> > Subject: Re: Triggers?
> >
> >
> > >
> > > We do this now, but you have to write a little
> > wrapper around the Java to
> > > get it to be called from the trigger.
> > >
> > > We've actually accomplished this on V5R1 via
> > creating a Java Stored
> > > procedure, and then calling that stored procedure
> > via an SQL trigger.
> > This
> > > is nice because the DB is managing the lifecycle
> > of the JVM, and I believe
> > > the startup cost of the JVM only has to be paid
> > once per job.
> > >
> > > We've also created a small externally defined
> > trigger in a high level
> > > language that actually calls/submits a call to run
> > a Java class.  This
> > > works ok as well, except that the JVM has to be
> > started for each call.
> > > That may not be an issue if this is on a slowly
> > changing file.
> > >
> > > I would just say that in either of these methods
> > you want to make sure
> > that
> > > you realize exactly how often this trigger is
> > going to be called.  It is
> > > very easy to end up in a bad situation if you
> > attach a trigger to a file
> > > that has transactions performed on it often.
> > You'll either slow down your
> > > operations tremendously using the first method, or
> > end up with too many
> > > jobs submitted for the system to handle in a
> > timely manner in the second.
> > > Just be careful!
> > >
> > > Chris DeLashmutt
> > > Senior R&D Analyst
> > > LeasePlan USA
> > > 1165 Sanctuary Pkwy., Alpharetta, GA 30004
> > > Phone: 678-202-8695
> > > Fax: 678-921-4895
> > > ClearCase problems? Check out the LeasePlan
> > ClearCase FAQ for answers!
> > >
> > >
> > >
> > >                       "cornelius, chad"
> > >                       <chad.cornelius@xxxxxxxxxx
> >      To:
> > "'java400-l@xxxxxxxxxxxx'" <java400-l@xxxxxxxxxxxx>
> > >                       tate.co.us>
> >      cc:
> > >                       Sent by:
> >      Subject:
> > Triggers?
> > >                       java400-l-bounces@midrange
> > >                       .com
> > >
> > >
> > >                       01/21/2005 12:13 PM
> > >                       Please respond to Java
> > >                       Programming on and around
> > >                       the iSeries / AS400
> > >
> > >
> > >
> > >
> > >
> > > Does anyone know if it is possible to create a
> > trigger that can execute a
> > > java class?
> > >
> > >
> > >
> > > Thanks,
> > >
> > > Chad
> > >
> >
> >
> > --
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>
>
>
>
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