Error: Kibana server is not ready yet

To troubleshoot the Kibana server is not ready yet error, try these steps:

From within a Kibana node, confirm the connection to Elasticsearch:
```
curl -XGET elasticsearch_ip_or_hostname:9200/
```
Guarantee the health of the three Kibana-backing indices. All indices must appear and display status:green and status:open:
```
curl -XGET elasticsearch_ip_or_hostname:9200/_cat/indices/.kibana,.kibana_task_manager,.kibana_security_session?v=true
```
These Kibana-backing indices must also not have index settings flagging read_only_allow_delete or write index blocks.
Shut down all Kibana nodes.
Choose any Kibana node, then update the config to set the debug logging.
Start the node, then check the start-up debug logs for ERROR messages or other start-up issues.

For example:
- When Kibana is unable to connect to a healthy Elasticsearch cluster, errors like master_not_discovered_exception or unable to revive connection or license is not available errors appear.
- When one or more Kibana-backing indices are unhealthy, the index_not_green_timeout error appears.

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