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From Rohit Yadav <rohit.ya...@shapeblue.com>
Subject [DISCUSS][ASK] Should agent wait for pending tasks on (mgmt server) disconnection?
Date Fri, 11 May 2018 10:55:10 GMT
All,


Historically, when the agent (kvm, ssvm, cpvm) is disconnected from the management server
(say due to mgmt server restart etc), the reconnection logic waits for any pending tasks/commands
to complete before reconnection attempts are made. I tried to search git history but could
not find a reason, can anyone share why we may need this?


Based on the reported issue:

https://github.com/apache/cloudstack/issues/2633


I've a working patch which removes this limitation:

https://github.com/apache/cloudstack/pull/2638


>From testing with various combinations of tasks, I found that when that happens even if
the pending task succeeds it fails to send an Answer to the mgmt server, therefore from the
control plane's perspective that task is still pending/on-going.


When the mgmt server comes back online, and the agent finally reconnects (pending on how long
the pending task took) the executed operation is still pending in mgmt server's view and may
sometimes require manual cleanups in database. By removing the limitation in above PR, at
least the agent reconnects faster while of the failure/fault behaviours remain the same. A
bigger design fix would be to make management server asynchronous of agent side answer/response
handling.


- Rohit

<https://cloudstack.apache.org>



rohit.yadav@shapeblue.comĀ 
www.shapeblue.com
53 Chandos Place, Covent Garden, London  WC2N 4HSUK
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