Default index pattern not being preserved across upgrades

[jayjanssen]

Kibana version:

Kibana 6.X (most recently on 6.4.0)

Elasticsearch version:

6.X

Server OS version:

Official Docker image

Original install method (e.g. download page, yum, from source, etc.):

Docker

Describe the bug:

Every time I upgrade Kibana (which runs in Docker for me), I have to re-set the Default index. All my other kibana settings (index pattern definitions, visualizations, dashboards, etc.) are preserved correctly. I run several kibana instances on the same cluster, so I set KIBANA_INDEX (differently) for each instance

KIBANA_INDEX=.kibana-1

Steps to reproduce:

1. Assume ES 6.4.0 is running with at least two indexes and can be reached at http://host.docker.internal:9200
2. docker run --name=kibana-test -p 1234:5601 -e ELASTICSEARCH_URL=http://host.docker.internal:9200 -e KIBANA_INDEX=.kibana-1234 docker.elastic.co/kibana/kibana:6.3.2
3. Go to http://127.0.0.1:1234, create two index patterns and set one as default index
4. docker stop kibana-test && docker rm kibana-test
5. docker run --name=kibana-test -p 1234:5601 -e ELASTICSEARCH_URL=http://host.docker.internal:9200 -e KIBANA_INDEX=.kibana-1234 docker.elastic.co/kibana/kibana:6.4.0
6. Revisit http://127.0.0.1:1234 and click 'Discover' -- you have to set the default index again.

Expected behavior:

I expect my default index setting to be stored like everything else, but it doesn't seem to be getting preserved.

Screenshots (if relevant):
Result of step 6:

Any additional context:
This is frustrating because I have several different Kibana instances that I upgrade all at once and I have to visit each of them to re-set the default index on every upgrade.

[evanfreed]

Adding a +1, I've seen a similar behavior when:

1. Exporting dashboards, visualizations, searches and index patterns through the Kibana Rest API to disk
2. Deleting all existing dashboards, visualizations, searches, and index patterns
3. Submitting all objects back through the API
4. Reopening Kibana and selecting dashboards fails due to not setting default index pattern.

[bmcconaghy]

@evanfreed so I have fixed the original issue related to migrations. I do not think your issue is related as I originally thought it might be, so would you mind submitting your issue as a new one and pinging me on it?

[spalger]

Reverted #23377