[kudu-CR] [location awareness] replica selection honors placement policy

["Alexey Serbin (Code Review)" <ge...@cloudera.org>]

Hello Will Berkeley, Kudu Jenkins, 

I'd like you to reexamine a change. Please visit

    http://gerrit.cloudera.org:8080/11207

to look at the new patch set (#6).

Change subject: [location_awareness] replica selection honors placement policy
......................................................................

[location_awareness] replica selection honors placement policy

This patch introduces placement policy into the catalog manager's
replica selection process. The replica selection logic is factored out
into the new PlacementPolicy class.

In essence (for details see [1]), the placement policy is about:
  * in case of N locations, N > 2, not placing the majority of replicas
    in one location
  * spreading replicas evenly among avaialable locations
  * within a location, spreading load evenly among tablet servers

This patch also adds a few test scenarios for the new functionality.

[1] https://s.apache.org/location-awareness-design

Change-Id: I4169098abf17d5591d4c1675561afc15b5477fcd
---
M src/kudu/master/CMakeLists.txt
M src/kudu/master/catalog_manager.cc
M src/kudu/master/catalog_manager.h
A src/kudu/master/placement_policy-test.cc
A src/kudu/master/placement_policy.cc
A src/kudu/master/placement_policy.h
M src/kudu/master/ts_descriptor.cc
M src/kudu/master/ts_descriptor.h
M src/kudu/master/ts_manager.cc
M src/kudu/master/ts_manager.h
10 files changed, 1,085 insertions(+), 194 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/07/11207/6
-- 
To view, visit http://gerrit.cloudera.org:8080/11207
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I4169098abf17d5591d4c1675561afc15b5477fcd
Gerrit-Change-Number: 11207
Gerrit-PatchSet: 6
Gerrit-Owner: Alexey Serbin <as...@cloudera.com>
Gerrit-Reviewer: Alexey Serbin <as...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Will Berkeley <wd...@gmail.com>