How to check about Redshift maintenance windows

Question

As usual we set Redshift maintenance windows on Saturday morning, and we got several errors during that maintenance windows time.

* Query Processing Error AM5:07:01
[Amazon](500051) ERROR processing query/statement. Error: Query execution failed
[SQL State=HY000, DB Errorcode=500051] 

* Connection Error AM5:07:27.79
[Amazon](500150) Error setting/closing connection: Connection refused: connect.

I guess that's due to Redshift internal maintenance. May I ask how to check any evidence to prove that on Redshift? I checked the svl_qlog with aborted=1, but couldn't find perfect one.

And is there any way to set maintenance window to skip when the user session is running on?

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Thanks to useful information from Schepo and Bill, we could prove that connection error was due to reboot on Redshift Maintenance Window. Also, we checked Redshift Event at Console, exactly what time Redshift reboot started and ended.

Answer 1

Another way to document that the maintenance window was used is to check the "healthy" dashboard metric on the console or in CloudWatch. If the cluster went unhealthy then returned to healthy during the maintenance window is very likely that AWS performed an update on the systems.

Answer 2

Probably the best way to check if the connection errors were due to Redshift maintenance would be to check the Maintenance tab in your cluster configuration. In the example screenshot below, it's some time between 06:30 and 07:00 am every Wednesday.

There's no way to stop it happening while user sessions are connected. Although you do have the option of deferring all maintenance for up to 45 days if you need (follow the Edit button on the same screen).

For evidence to prove, you can check the audit log of past maintenance events by looking in the AWS Config service under the "timeline" of your cluster. Follow the View Config Timeline button to open AWS Config for that cluster. In the below example screenshot you can see the exact time (08:49:20) of one maintenance window in the past.