Config setting 'server.defaultRoute' ignored

[peterpramb]

Kibana version:
7.5.0

Elasticsearch version:
7.5.0

Server OS version:
RHEL 7.6

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

Describe the bug:
According to #44678 an available config setting server.defaultRoute should be automatically mapped to an UI's advanced setting. Unfortunately this is not the case, and the setting is ignored alltogether, letting Kibana start with just the default route.

Additionally server.defaultRoute is gone alltogether from the documentation (https://www.elastic.co/guide/en/kibana/master/settings.html) without being mentioned in Breaking Changes.

Steps to reproduce:

1. Set in Kibana config: server.defaultRoute: "/app/monitoring"
2. Login in to Kibana: Start application is /app/kibana
3. Advanced settings show: defaultRoute = /app/kibana

Expected behavior:
Kibana starts with /app/monitoring

Screenshots (if relevant):

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)

[legrego]

@peterpramb,

Thanks so much for the bug report, and I'm sorry this ended up causing you problems. @restrry identified the issue and has merged a fix, which will be available in the 7.5.1 release.

Additionally server.defaultRoute is gone alltogether from the documentation (elastic.co/guide/en/kibana/master/settings.html) without being mentioned in Breaking Changes.

We migrated server.defaultRoute to uiSettings.overrides.defaultRoute in 7.5.0, so that it behaves in a way that does not introduce breaking changes. I wanted to remove it from the documentation so that folks just getting started don't end up configuring Kibana in a way that won't work in the near future.
Perhaps the more pragmatic solution would have been to keep the setting in the docs, but mark it as deprecated instead for the remainder of 7.x.

#46787 will introduce the actual breaking change of not supporting server.defaultRoute altogether. We do our best to reserve breaking changes for major version releases, so expect #46787 to happen for 8.0.0

[legrego]

Workaround

For anyone else running into this for 7.5.0 before 7.5.1 is available:

You can workaround this by changing server.defaultRoute to uiSettings.overrides.defaultRoute in your kibana.yml file:

# before
server.defaultRoute: /app/monitoring

# after
uiSettings.overrides.defaultRoute: /app/monitoring