Add Force Merge to hot lifecycle phase

[mud5150]

Add Force Merge to hot lifecycle phase:
For time series data it makes sense that you may want to do a force merge on an index in the hot phase after rollover occurs. Seems pretty straight forward but if you want more information LMK.

[elasticmachine]

Pinging @elastic/es-core-features

[dakrone]

For time series data it makes sense that you may want to do a force merge on an index in the hot phase after rollover occurs.

@mud5150 will doing a hot phase with a rollover action and then having a "warm" phase with no min_age set so that it performs the force merge immediately after the rollover happens work? You can do that currently. Is there a reason the force merge would need to happen in the hot phase?

[mud5150]

It could work, however in my particular instance all phases are in use. In my instance "hot" servers hold 28 days of data. Warm servers (slower disks) hold the rest of the year and still get a good amount of user queries. Cold nodes have slow disks and high ratio of storage to memory, use frozen indices, etc. It's not a problem for me to have curator force merge the index after the rollover happens, I just thought the above seems like a reasonable use case.

[dakrone]

We discussed this and decided to allow the force merge action in the hot phase, with a small caveat. We will require that the rollover action also be present (since rollover will occur prior to the force merge).