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| nelson |
 Posted: Mon Jan 12, 2015 10:24 am Post subject: Sender channel to multiple IPs |
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Partisan
Joined: 02 Oct 2012
Posts: 313
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Hi All,
If I have a sender channel pointing to a host/ip, and a DNS is who redirects the connection to QM1 on host 1 (IP1/1414) or the QM1 on host 2 (IP2/1414), the sequence of the messages will be lost?
I just want to confirm that this does not work the same as if we specify two IPs on the sender channel.
Thanks in advance |
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| mqjeff |
| Posted: Mon Jan 12, 2015 10:26 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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There are several ways to make QM1 highly available.
If you use multi-instance, it will have two separate IP addresses.
If you use something other than multi-instance, it likely won't.
You should not simply make two separate QM1s on different hosts. |
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| nelson |
| Posted: Mon Jan 12, 2015 10:30 am Post subject: |
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Partisan
Joined: 02 Oct 2012
Posts: 313
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Thanks mqjeff,
We know there are another (better) options... but... for the meantime this is what we have  .
The two approaches would work? or only the second one (multiple IPs on the sender channel)? |
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| PaulClarke |
| Posted: Mon Jan 12, 2015 10:47 am Post subject: |
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Grand Master
Joined: 17 Nov 2005
Posts: 1002
Location: New Zealand
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nelson,
Essentially both solutions are very similar. You can specify a single host address and have a DNS server (or something) routing you to the right back-end IP address. Or you can specify two IP addresses on the channel.
In the first approach you can have DNS (or workload balancer) making an intelligent decision about where to route the connection. In the IP list case you will just get MQ trying the first connection and then the second.
The key thing is what are you connecting to. If it's the same Queue Manager that can locate on different machines (such as multi-instance) then all will be well. If it is two different Queue Managers which just share the same name then sooner or later bad things will happen. You are never recommended to have two different Queue Managers with the same name.
Cheers,
Paul.
_________________
Paul Clarke
MQGem Software
www.mqgem.com |
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| nelson |
| Posted: Mon Jan 12, 2015 11:54 am Post subject: |
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Partisan
Joined: 02 Oct 2012
Posts: 313
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Thanks Paul,
This is a long story... The secondary site is in a separate network and we were not able to make one system visible to the other. Of course, there is no data replication. But our main concern is to make this switch the less painful possible, and if possible, with no manual intervention. Our first worry is the channels sequence... Apart form that, it's OK to us if the connectivity keeps alive to one or other queue manager.
Thanks for your advises! |
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| PaulClarke |
| Posted: Mon Jan 12, 2015 12:12 pm Post subject: |
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Grand Master
Joined: 17 Nov 2005
Posts: 1002
Location: New Zealand
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If the two QM1 Queue Managers are different Queue Managers then when the sender channel makes the switch you will almost certainly get channel sequence errors and the channel will fail to start.
_________________
Paul Clarke
MQGem Software
www.mqgem.com |
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| nelson |
| Posted: Mon Jan 12, 2015 12:15 pm Post subject: |
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Partisan
Joined: 02 Oct 2012
Posts: 313
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| So.. there is no other way more than resetting the channels? |
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| PaulClarke |
| Posted: Mon Jan 12, 2015 1:16 pm Post subject: |
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Grand Master
Joined: 17 Nov 2005
Posts: 1002
Location: New Zealand
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Well, if you only ever send non-persistent messages down a NPMSPEED(FAST) channel then you would be ok.
Alternatively you could use cluster channels and you'll be ok.
But, a normal sender/receiver channel sending persistent message then you will get sequence number erorrs. You can, of course, write a channel exit or channel event handler to automatically issue the reset channel. Of course the sequence number failures are there for a reason to alert you to the possibility that something has gone wrong. So, bypassing them may not be ideal.
The other problem you face is that, if the back end QMs are different, that if the channel end indoubt then there is a danger than messages will be duplicated.
Cheers,
Paul.
_________________
Paul Clarke
MQGem Software
www.mqgem.com |
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| nelson |
| Posted: Mon Jan 12, 2015 1:34 pm Post subject: |
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Partisan
Joined: 02 Oct 2012
Posts: 313
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| Paul. We will take all your advises into consideration. Thanks a lot for your time. |
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| mqjeff |
| Posted: Mon Jan 12, 2015 1:36 pm Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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You can also very easily run into messages that are stuck on one server, or different messages stuck on both servers.
So when you switch, or switch back, you could lose the most recent set of messages, and start processing messages that were left the last time you switched. |
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