Kibana server not ready after update to 7.15

I upgraded my ELK-Stack from 7.14 to 7.15. There are two Elasticsearch nodes (1 hot / 1 warm) and a kibana server.
From the kibana server on the web-interface i get just the message "Kibana server is not ready yet" and in the logs from kibana after a while from starting kibana I have this messages:

{"type":"log","@timestamp":"2021-10-12T15:12:32+02:00","tags":["error","savedobjects-service"],"pid":649,"message":"[.kibana_task_manager] Action failed with 'Request timed out'. Retrying attempt 2 in 4 seconds."}
{"type":"log","@timestamp":"2021-10-12T15:12:32+02:00","tags":["info","savedobjects-service"],"pid":649,"message":"[.kibana_task_manager] REINDEX_SOURCE_TO_TEMP_INDEX_BULK -> REINDEX_SOURCE_TO_TEMP_INDEX_BULK. took: 122022ms."}
{"type":"log","@timestamp":"2021-10-12T15:12:32+02:00","tags":["error","savedobjects-service"],"pid":649,"message":"[.kibana] Action failed with 'Request timed out'. Retrying attempt 2 in 4 seconds."}
{"type":"log","@timestamp":"2021-10-12T15:12:32+02:00","tags":["info","savedobjects-service"],"pid":649,"message":"[.kibana] REINDEX_SOURCE_TO_TEMP_INDEX_BULK -> REINDEX_SOURCE_TO_TEMP_INDEX_BULK. took: 122156ms."}

Can you help me to fix this issue?

Regards
Peter

Hi,

Could you please restart kibana and share the complete logs after giving it some time to initialise after the upgrade action?

Cheers

Thank you for the response.
In the meantime i've found the problem. My Elasticsearch node had a diskusage of 90% and had a warning because of this. After expanding the disk everything was fine again.