Add bookkeeperClientRegionawarePolicyEnabled and bookkeeperClientReor…

[cbornet]

…derReadSequenceEnabled config parameters

Fix #3119

Motivation

This allows to configure region-aware policy and read-reordering so that brokers first read on bookies of their own region.

Modifications

• Added parameters:

# Enable region-aware bookie selection policy. BK will chose bookies from
# different regions and racks when forming a new bookie ensemble
# If enabled, the value of bookkeeperClientRackawarePolicyEnabled is ignored
bookkeeperClientRegionawarePolicyEnabled=false

# Enable/disable reordering read sequence on reading entries.
bookkeeperClientReorderReadSequenceEnabled=false

• Fixed bug in ZkBookieRackAffinityMapping: the value set to racksWithHost by deserialize() was overriden by the affectation in setConf(). The fix just moves the hostname workaround in setConf().

Result

Users can enable bookkeeperClientRegionawarePolicyEnabled and bookkeeperClientReorderReadSequenceEnabled to make brokers read on bookies of their own region