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MQSeries.net Forum IndexWebSphere Message Broker SupportParallel processing + 2 MQ Input Nodes +additional Instance

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Additional Instances with multiple Input Nodes is tricky :)
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mehta10987
PostPosted: Thu Aug 13, 2020 7:05 pm Post subject: Parallel processing + 2 MQ Input Nodes +additional Instance Reply with quote

Novice

Joined: 12 Oct 2019
Posts: 13
Location: USA

Hello GrandMasters,
looking for clarification with one of the scenario.

I have a Message Flow with two MQ Input Nodes.
MQ Input Node1: is listening to Queue1
MQ Input Node2: is listening to Queue2

If I create 10 additional Flow level Instances, How many messages can be picked at once by this flow?

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abhi_thri
PostPosted: Sat Aug 15, 2020 8:08 am Post subject: Reply with quote

Partisan

Joined: 17 Jul 2017
Posts: 396
Location: UK

hi...it depends on which input thread gets initialized first and on the queue depths, it is covered at the below info center topic.

https://www.ibm.com/support/knowledgecenter/SSMKHH_10.0.0/com.ibm.scenarios.doc/Subflows/topics/scnsubflows_01_28_.htm

Also see the ibm feedback my esteemed colleague had added there,

When additional instances are set at the flow level, they are shared between the input nodes in the message flow. This does not mean that the extra threads will freely swap between input nodes, but rather that the additional threads will be spawned where needed. This can lead to "thread starvation", where one very active input "consumes" the available thread pool, which effectively "starves" the other input of available additional threads.

When additional instances are set at the flow level and when you set the property - Start additional instances when flow starts, when the message flow is started, the first input node to get initialized would start all the additional instances - because Input node's thread pool is associated with the message flow pool (the default config of Input node). When the second or subsequent input nodes get initialized, they would find that the required no. of additional threads are already started at the flow pool level, they would not separately start any new additional threads. This is an expected behaviour.

If you are looking to ensure thread availability for multiple inputs in a deterministic manner, we recommend either setting additional instances at the node level, or separating in the inputs into separate flows. That would avoid the thread starvation kind of situation if the instances were defined at the flow level where one of the Input nodes can take away a large no. of threads.
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rekarm01
PostPosted: Mon Aug 17, 2020 10:08 am Post subject: Re: Parallel processing + 2 MQ Input Nodes +additional Insta Reply with quote

Grand Master

Joined: 25 Jun 2008
Posts: 1396

mehta10987 wrote:
If I create 10 additional Flow level Instances, How many messages can be picked at once by this flow?

Twelve. One for Node1, one for Node 2, and ten additional instances.

No matter how the execution group allocates the additional instances among the nodes, there would never be more than twelve total instances.
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