[Maps] Simplify EMS config for on-prem configs

[thomasneirynck]

Describe the feature:

Currently, EMS needs to be configured with three URLs.

map.emsFileApiUrl
map.emsTileApiUrl
map.emsFontLibraryUrl

There's also a link to the public website:

map.emsLandingPageUrl

These are all undocumented internal configs.

Describe a specific use case for the feature:

As EMS will become available on-prem, we can simplify this config to a single setting. All 4 resources will be hosted locally then.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[thomasneirynck]

I'd propose the following:

1. Introduce new publicly documented setting:

map.emsUrl: http://localhost:8080

From these, the 4 endpoints will be dynamically constructed:

-> FileApiUrl: append tile.
-> TileApiUrl: append file
-> Font api: append tile/fonts/{fontstack}/{range}.pbf
-> landing page: append maps

2. Retain the original settings. These will remain internal and undocumented.

map.emsFileServiceUrl
map.emsTileServiceUrl
map.emsFontLibraryUrl
map.emsLandingPageUrl

These are hardcoded in the Kibana source-code.

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Why can we not just introduce maps.emsUrl and remove the 4 legacy settings?

For the publically hosted EMS, the files, tiles, and landing page all reside on a different host. There is not really an algorithmic way to construct the urls from a root path. Also, it might still be useful to configure these in isolation so we can test staged or test versions of the tile and file service.

[nickpeihl]

lgtm.

1. Introduce new publicly documented setting:

map.emsUrl: http://localhost:8080

Should this new setting also be restricted to the specific license for on-prem maps?

From these, the 4 endpoints will be dynamically constructed:

-> FileApiUrl: append tile.
-> TileApiUrl: append file
-> Font api: append file/fonts/{fontstack}/{range}.pbf
-> landing page: append v7.10 (or whatever the version number)

Couple of endpoint corrections:
Font api: append /tile/fonts/{fontStack}/{range}.pbf
landing page: append /maps (no version number necessary)

[thomasneirynck]

thx, added the corrections.

Should this new setting also be restricted to the specific license for on-prem maps?

Interesting. What should the behavior be? Log a warning to the console?

[nickpeihl]

Interesting. What should the behavior be? Log a warning to the console?

I was thinking we could log a warning, but I don't feel too strongly about this. License verification should already be handled by the on-prem maps service.

[thomasneirynck]

+1 on warning to console. It'd be helpful agreed.

[jsanz]

Since there's a license check in the OnPrem EMS, I think it would make sense to also check it on the Kibana side to honor the setting only for enterprise level clusters.