Force a failover on a mirror?

Question

Question

Dan Pahnke · Mar 31, 2020

#Mirroring #InterSystems IRIS #InterSystems IRIS for Health

Is there a way to force a failover from the primary mirror member to the backup member without forcing down the primary (which happens with ##class(SYS.Mirror).BecomePrimary())? What I'm trying to simulate is a network isolated condition on the primary.

Discussion (6)1

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Vic Sun · Mar 31, 2020

Hello Dan,

I am struggling to understand the scenario that you are testing/planning for. Do you have an arbiter? I would read through the mirroring docs which discuss the various options available to you and the various automatic responses that mirroring can take (including some diagrams).

https://cedocs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=GHA_mirror

https://cedocs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=GHA_mirror#GHA_mirror_set_autofail_outages

If you want to simulate network isolation, I think you'd need to actually network isolate. If you force the backup to become primary, Caché will try to force down the original primary to prevent split brain.

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score 0 · Answer 1 · 2020-03-31T16:27:39-04:00

Thanks Vic,

What I was looking for was a way to, in effect, swap which member was primary and which was backup. Taking your advice and re-reading the Automatic Failover Mechanics section of the docs I've decided that there is no need for my test.

Thanks again.

Dan

score 1 · Answer 2 · 2020-03-31T16:32:40-04:00

Happy to help! For what it's worth, best practice to initiate a failover would be to simply cleanly shut down the primary.

score 0 · Answer 3 · 2020-04-29T08:14:49-04:00

Also when we are testing our scenarios we do phisically sometimes execute the network isolation amongst other tests

score 0 · Answer 4 · 2020-05-20T18:50:52-04:00

Have you considered in using the ^MIRROR routine utility in %SYS on the secondary mirror member to manually force it to become the primary member?

read more here https://docs.intersystems.com/irislatest/csp/docbook/Doc.View.cls?KEY=GH...

score 0 · Answer 5 · 2020-05-20T19:16:42-04:00

That routine ultimately uses the same API under the covers: ##class(SYS.Mirror).BecomePrimary(), which forces down the original primary.