[QiuMM]

Currently, we need to do like below when specify the SegmentWriteOutMediumFactory, which is terrible.

druid.peon.defaultSegmentWriteOutMediumFactory.@type: offHeapMemory

Besides, this PR also fixes the docs about SegmentWriteOutMediumFactory.

[leventov]

@QiuMM please don't specify milestones for any non-bug PRs. I know that a lot of people do this, but it's a bad practice. See https://groups.google.com/d/msg/druid-development/QPZUIzLtZ2I/eZyw8BoVCgAJ.

[fjy]

@leventov strongly disagree. I think where possible we should try to assign milestones to PRs we want to get in and aim to have the PR reviewed and merged before then. If the PR needs to be pushed back to a future release we can always do that.

[QiuMM]

@leventov although this PR did not fix bug in the code, it fixed the docs. There is no effect when specify value for druid.peon.defaultSegmentWriteOutMediumFactory unless set value for druid.peon.defaultSegmentWriteOutMediumFactory.@type, but people do not know it. So this PR fixed this thing and because @type looks strange then I modified it. Since this PR is important(I think), I added this to the 0.13.1 milestone.

[jihoonson]

LGTM. I'm merging this PR.

Regarding milestone, @leventov started a thread on our dev mailing list (http://mail-archives.apache.org/mod_mbox/druid-dev/201811.mbox/%3CCAAMLo=Y_d1tXtgWpt_E7uD7zwh6=rDop-B_3O73HnQwBMRo2TQ@mail.gmail.com%3E), and so we can continue discussion there.