'Kibana server is not ready' after 7.7.1-7.8.1

[Gavin_Clark]

After experiencing slowness in the Kibana UI from the jump from 6.8.9 to 7.7.1, I was told on the forums I should upgrade to 7.8 as that had a number of UI performance improvements. All elasticsearch nodes were upgraded from 7.7.1 -> 7.8.1, and then I updated Kibana to 7.8.1.

Kibana has been sitting at 'Kibana server is not ready' for over an hour now. I've stopped and restarted the service to no avail. In the journalctl log I keep seeing the following repeating:

Aug 05 21:36:09 kibana kibana[7573]: {"type":"log","@timestamp":"2020-08-05T21:36:09Z","tags":["info","savedobjects-service"],"pid":7573,"message":"Detected mapping change in \"properties.namespaces\""}

The upgrade for elasticsearch was missed on the Kibana node unfortunately. Upon the realization, I killed the Kibana service, upgraded elasticsearch and then restarted kibana but it seems the damage has already been done.

How do we get Kibana back up and running?

[Gavin_Clark]

Digging a bit more into the logs I see:

Another Kibana instance appears to be migrating the index. Waiting for that migration to complete. If no other Kibana instance is attempting migrations, you can get past this message by deleting index .kibana_task_manager_3 and restarting Kibana."}

Can I delete kibana_task_manager_3 safely without losing my saved objects? What exactly does the kibana_task_manager contain?

[Gavin_Clark]

I was able to resolve my issue by running the following:

curl -XDELETE http://localhost:9200/.kibana_task_manager_3

A LOT of places online were recommending deleting the main .kibana index to resolve the issue which as I understand it will cause you to lose all of your saved indexes, visualizations etc. This solution was much less heavy handed.