Re: Multiple instances and background batch threads.
Re: Multiple instances and background batch threads.
- Subject: Re: Multiple instances and background batch threads.
- From: Chuck Hill <email@hidden>
- Date: Thu, 9 Oct 2008 11:15:38 -0700
On Oct 8, 2008, at 6:03 PM, Miguel Arroz wrote:
Hi!
We have some "request" entities to handle communication between
real apps and the helper apps. The real app creates a request object
and stores it on the DB. Helper apps check the DB every 5 seconds or
so for unprocessed requests. I've found some advantages on this:
- If processing goes wrong, you can store information about the
error on the request itself and mark it as being in error state.
That helps tracking down problems.
- It can be used to establish priorities, like sorting the requests
for some kind of priority rules and always picking up the highest
priority one.
- We still haven't made this, but theoretically it's an easy way to
load-balance tasks, if that is needed, across multiple instances. As
you have full control over the semantics of the requests, you can
launch several instances with different configurations (maybe using
command line arguments) and each instance can be smart enough to
process only the requests that should be processed by it. This
solves the problem of load balancing *and* making sure you don't
have more than one instance making raw processing on the same data,
as you would control that. Again, this paragraph is only
theoretical, there may be something fundamentally wrong with this
that I'll only find out when implementing, but it seems a great
idea. ;)
That is how I have mine set up. I have not gotten to the point of
partitioning some of the threads into a second instance, but it is
setup to handle it.
Chuck
On 2008/10/09, at 01:40, Josh Paul wrote:
+1
We have a DirectAction that allows for apps to call in when the
process(ing) is needed.
On Oct 8, 2008, at 5:11 PM, Chuck Hill wrote:
So far that has worked for me as well.
Chuck
On Oct 8, 2008, at 5:00 PM, Miguel Arroz wrote:
Hi!
We have separate applications that handle that kind of tasks.
Each of those applications will have only one instance running.
No locking needed, no database channel congestion on "real"
application instances, etc.
Yours
Miguel Arroz
...........................
http://www.survs.com
On 2008/10/09, at 00:49, Q wrote:
I have a scenario where I need my application to periodically
fire off background batch tasks in a separate thread, but only
need one of the possible instances to perform this task at any
given interval. What technique do people normally use with WO
to perform this sort of election/locking between instances so
that only one of them at a time ever attempts to do the work?
--
Seeya...Q
Quinton Dolan - email@hidden
Gold Coast, QLD, Australia (GMT+10)
Ph: +61 419 729 806
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--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve
specific problems.
http://www.global-village.net/products/practical_webobjects
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Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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