[CCR] Edit follower index: advanced settings are not persisted

[sebelga]

When editing a follower index and changing an advanced setting, the changes is not persisted.

Changing "Max read request operation count" to 2000

Once saved, the value is still 5120

[elasticmachine]

Pinging @elastic/es-ui (Team:Elasticsearch UI)

[cjcenizal]

Looks like this bug is on the ES side: elastic/elasticsearch#54996. This manifests in the UI because creating a follower index performs a create request and then a fetch request in rapid succession. When the new follower index is fetched it's in a paused state (which ES later changes to an active state). When you then edit the new follower index it's still in this stale paused state, which means there's no advanced settings data to populate the form.

[sebelga]

Thanks for investigating. I do think our UI should handle this so the user does not think there is a bug and the follower index hasn't been updated.
A solution is, after editing a follower index, have a request polling in the details flyout and wait until the follower index is active again to display the stats. WDYT?

[sebelga]

I have been playing around and it is clearly a bug.

I have manually done all the steps in console and they work as expected, the value gets updated (here max_read_request_operation_count set to 2000)

Once we edit the follower index in the UI, don't touch anything and click "Update", we reverted the updated values to the default ones.

[cjcenizal]

Thanks for digging deeper @sebelga! I found the problem. When we migrated the server to NP we left out some route validation that strips the body from the requests (https://github.com/elastic/kibana/pull/60121/files#diff-8ae5a51616bdcb1706f0aaf1ab1581c9R173). I'll get a fix up shortly.