azureazure-virtual-machineazure-autoscaling-block

Azure VMs unexpected shutdown while AutoScaling


Today we had an issue with Azure VMs where one VM in availability set of 2 just stopped responding. After few mins we noticed that machine was shutdown and the other VM in the set wasn't turned on (which should be ok as this isn't a failover). We have take a look at the VM monitoring and there wasn't a single log telling us that there was any downtime. The only thing that we found is 2 strange logs in the Management Services - Operation Logs.

The first one was with following details:

Description: The autoscale engine attempting to scale resource 'xyz' from 0 instances count to 1 instances count.

LastScaleActionTime: 20131106T173020Z

NewInstancesCount: 1

OldInstancesCount: 0

Second one:

The autoscale engine attempting to scale resource 'xyz' from 2 instances count to 1 instances count.

LastScaleActionTime: 20131112T203656Z

NewInstancesCount: 1

OldInstancesCount: 2

Does anyone know what may had happen ?

UPDATE

Azure Support has provided me with the feedback and they explained that machines were down due to host update.

Regards


Solution

  • Both of my machines were down because of the host update and AutoScaling set from 1 to 2 machines based on CPU usage. So I have found out that AutoScaling won't turn the second machine on when doing host update (which can be pretty helpful and make my apps online).

    I think that will explain the 0 of 1 instances issue, so don't use AutoScaling with above setup to get HA.

    Regards