commit 64592274ac4ee5bff4c01807602e6e39714a0f80
author ningw <1994wangning@gmail.com> Mon Nov 16 00:13:18 2020 +0800
committer Andrew Wong <awong@cloudera.com> Thu Nov 26 02:12:52 2020 +0000
tree 5566aa8b354b7f97ae772b8f7bce7c55a176ba8a
parent fd863bb674c01bc792571032f7233ed45e9c9b12

KUDU-3214 Parallelize DownloadWALs in tablet copy operation

Make DownloadWALs operation in parallel.

Add tests:
  - Correctly collect status of parallelized DownloadWALs.
  - Random inject latency and heavy insert.
  - Random inject latency and heavy update.

Perf: Timing download a tablet without any block data.
WAL size (In MB)         575     1149     2183
WAL count                87      174      348
In seq:                  3.417s  6.404s   12.371s
In parallel(4threads):   2.543s  4.858s   8.761s

About 25% promotion.

Change-Id: Ib513118d233efdf4be7cbb0b790354c4c3e1bd84
Reviewed-on: http://gerrit.cloudera.org:8080/16726
Tested-by: Andrew Wong <awong@cloudera.com>
Reviewed-by: Andrew Wong <awong@cloudera.com>