Expose ignore_throttled as an option for _msearch

[s1monw]

In elasticsearch starting with version 6.6 we have a new beta feature called frozen indices. Frozen indices will not be search on by default unless a the request option ignore_throttled=false is set. This is mainly to protect users from running slowish requests with a index pattern etc. Yet, frozen indices also have a protection that allows fast evaluation of date-ranges which makes it suitable for kibana since even if a pattern expands to a frozen index the query will be likely very fast unless it can match. Yet, before we enable anything by default we should at least have an option to opt-in to this feature similar to what we have done here This would allow folks to try frozen indices through kibana. Down the road we might even enable this feature by default.

[elasticmachine]

Pinging @elastic/kibana-app

[timroes]

As of a discussion with PMs we just decided, that we will add a new setting to Kibana "Search in Frozen index" (name is WIP), which will default to off. A user can enable this (on a per space level, as most of the settings), and if that's enabled we will add the ignore_throttled=false parameter to all current Kibana App places (Graph, Courier, TSVB, Timelion), that execute an _search or _msearch request.

[s1monw]

++ thanks @timroes

[AlonaNadler]

@grabowskit @alexfrancoeur @tsg @tbragin above is our plan for frozen indices in Kibana. The first phase will include a global setting that enables search on frozen indices, in the future and based on feedback we might consider making this setting per index pattern.
Please let us know if you have any other considerations we should take into account

[alexfrancoeur]

Thanks for the ping @AlonaNadler. If this is enabled, do we have to worry about client side timeouts at all? Do we need to consider any of these changes for reporting (CSV & PDF)?

[tbragin]

cc @makwarth @roncohen @alvarolobato FYI