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| amqsclm to make queue managers CA |
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| abd.wsu |
 Posted: Wed Feb 11, 2015 10:11 am Post subject: amqsclm to make queue managers CA |
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Acolyte
Joined: 12 Sep 2012
Posts: 65
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We are planning to use amqsclm to achieve HA in our infra.
Here's the setup:-
We have two queue managers in cluster with all the same objects. And we are running the amqsclm program to move the messages across.
We have applications using JMS connection factories, Tomcat applications and stand alone java applications.
We have achieved some kind of reconnect capabilities with the JMS conn and Tomcat applications.
Right now, we have identified two problems with our setup.
1) Message sequencing
2) amqsclm not routing to queues if the listeners/apps are not connected long enough.
Is there a work around for either of these? Is this a good idea to achieve HA/CA? |
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| Vitor |
| Posted: Wed Feb 11, 2015 10:18 am Post subject: Re: amqsclm to make queue managers CA |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| abd.wsu wrote: |
Right now, we have identified two problems with our setup.
1) Message sequencing
2) amqsclm not routing to queues if the listeners/apps are not connected long enough. |
1) Message sequencing (better known as "message affinity") is a bad practice. Messages should not be reliant on other messages and one of the key reasons is exactly the problem you've found here. If you want to use this solution, redesign your applications not to use affinity
2) The amqsclm is a sample application. If it doesn't behave how you want, change it or write your own application.
| abd.wsu wrote: |
| Is this a good idea to achieve HA/CA? |
Frankly, no. It's based on the assumption that HA is at the application level. If one of the queue managers in the cluster fails then no application, amqsclm or otherwise, will be able to redirect the messages currently in that queue manager's queues to the other one. Those messages are effectively "lost" until the queue manager is restarted, and if the queue manager can't be restarted (e.g. disc error) then they're absolutely lost.
WMQ clusters for HA; they're not intended for HA and it comes at a price. It all depends how much HA you want.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| abd.wsu |
| Posted: Wed Feb 11, 2015 10:58 am Post subject: |
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Acolyte
Joined: 12 Sep 2012
Posts: 65
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Hi Vitor,
I am not sure message sequencing is message affinity. By message sequencing i mean application expecting messages in a particular order. ex: message 2 should come after message 1 and before message3 etc.
We had tried with a script to toggle the CLWLPRTY between the 2 queue managers and it was working fine but ti was complex and had it's own short comings. That's why we are thinking about amqsclm. When you say we can change it, do you mean tweak the parameters it takes?
I know MQ can never be complete HA but we want our applications to have no hiccups when one queue manager goes down. We are not worried about the messages sitting on the queue manager that went down. Almost all of the messages are persistent. |
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| mqjeff |
| Posted: Wed Feb 11, 2015 11:08 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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MQ can be complete HA, if you use a mixture of Clustering and multi-instance and your applications make use of more than one connection.
amqsclm has source code, so you can change the program.
Message sequencing is bad, too, and is best handled using MQ grouping. Then you can tell the cluster to send all messages for one group to one qmgr. |
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| bruce2359 |
| Posted: Wed Feb 11, 2015 11:55 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9396
Location: US: west coast, almost. Otherwise, enroute.
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| abd.wsu wrote: |
Hi Vitor,
I am not sure message sequencing is message affinity. By message sequencing i mean application expecting messages in a particular order. ex: message 2 should come after message 1 and before message3 etc. |
In your example, message 1 must precede message 2; and 2 must precede 3.
These messages have affinity to each other.
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| Vitor |
| Posted: Wed Feb 11, 2015 1:35 pm Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| abd.wsu wrote: |
| I am not sure message sequencing is message affinity. By message sequencing i mean application expecting messages in a particular order. ex: message 2 should come after message 1 and before message3 etc. |
I'm sure that's affinity.
| abd.wsu wrote: |
| We had tried with a script to toggle the CLWLPRTY between the 2 queue managers and it was working fine but ti was complex and had it's own short comings. That's why we are thinking about amqsclm. When you say we can change it, do you mean tweak the parameters it takes? |
No, I'm saying you can change the source code and build it again, or build your own application to perform this task. The amqsclm is intended to demonstrate capabilities, nothing more. If it happens to meet your needs, good. If it doesn't, change it.
| abd.wsu wrote: |
| I know MQ can never be complete HA but we want our applications to have no hiccups when one queue manager goes down. We are not worried about the messages sitting on the queue manager that went down. Almost all of the messages are persistent. |
Are you still not worried if the queue manager never comes up again? In that instance, even persistent messages are lost.What about if it takes you hours or even days to restart the failed queue manager? What's the impact to the business of those messages not being processed?
_________________
Honesty is the best policy.
Insanity is the best defence. |
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