Migrations should have a basic UI

[chrisdavies]

@bmcconaghy pointed out that migrations may take a while on a med-large size Kibana index. Currently, Kibana doesn't serve any HTTP requests until migrations are complete.

Many customers will probably think Kibana is hanging and just restart Kibana without checking the logs, and they will then end up in a: "It looks like another Kibana instance is migrating..." state.

We need to serve up some sort of "Migrations in progress" screen or we'll end up with a lot of support issues.

The screen should poll for completion of the migration.

A secondary concern that I should note here is that some people might be hosting Kibana in a system that automatically restarts it if it doesn't respond to HTTP requests. (At least, I've hosted complex web apps with such a setup before.) In such a case, such automation will kill Kibana in the middle of migrations and leave it in a hanging state.

[elasticmachine]

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

[tylersmalley]

@rudolf, feel free to close this if you don't think it's necessary at this point.

[pgayvallet]

We need to serve up some sort of "Migrations in progress" screen or we'll end up with a lot of support issues.

ATM SO migration is performed during the start phase of core, maybe even before the http service is started. Not saying do or don't, but this would mean major changes in the startup mechanism. That would also probably mean another bundle/ webpack entrypoint for this 'migration in progress' page.

[pgayvallet]

Zero downtime migrations are already a thing on serverless, and they may become standard for traditional deployments too.

With that in mind, I think it is fairly unlikely we'll ever need that kind of "migration in progress" UI. At best, we would have a "migration status" somewhere in the management sections, but we can discuss more about that when the time will come.

Until then, I'll go ahead and close this.