[0.89-fb] [master] Faster region assignments on cluster start up.

Author: aaiyer

Summary:
Neptune seems to wait for 1 min to assign regions.  This is because
we may have to wait for 1 min for the root/meta scanner to kick in.The first "initialChore()" does nothing.

We will now force this to happen once the root region is assigned, so
no more wait time.

Test Plan:
push to dev cluster and ensure that the assignments happen
immediately

Before, on the DL:

Mon Oct 15 16:15:34 PDT 2012 Starting master on hbasectrl049.ash3.facebook.com
ulimit -n 131070
2012-10-15 16:15:35,419 INFO org.apache.hadoop.hbase.master.HMaster: vmName=Java HotSpot(TM) 64-Bit Server VM, vmVendor=Sun Microsystems Inc., vmVersion=14.0-b16

2012-10-15 16:15:52,266 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region -ROOT-,,0.70236052 to hbase785.ash3.facebook.com,60020,1350342951149
2012-10-15 16:16:36,302 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region .META.,,1.1028785192 to hbase876.ash3.facebook.com,60020,1350342952955
2012-10-15 16:16:36,827 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region MailBox_cell5_v1,008253c7,1312525731978.16bdfc0d71605295f5273f081a27ddf5. to hbase788.ash3.facebook.com,60020,1350342951539
2012-10-15 16:16:36,929 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region MailBox_cell5_v1,005d1745,1312599894588.741e963357e1ed21adc32445a8e51ccc. to hbase861.ash3.facebook.com,60020,1350342954660
2012-10-15 16:16:36,940 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region MailBox_cell5_v1,00f2094d,1312598270719.403925907768ea37b3d3ea81945378a2. to hbase803.ash3.facebook.com,60020,1350342952550
2012-10-15 16:16:36,957 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region MailBox_cell5_v1,004a7904,1312599894588.20f71255cbf222cee51a684525c3d2ac. to hbase789.ash3.facebook.com,60020,1350342951574

After, on the test cluster:

Tue Oct 16 16:22:25 PDT 2012 Starting master on hbasedev130.ash3.facebook.com
ulimit -n 131070
2012-10-16 16:22:25,771 INFO org.apache.hadoop.hbase.master.HMaster: vmName=Java HotSpot(TM) 64-Bit Server VM, vmVendor=Sun Microsystems Inc., vmVersion=14.0-b16

...

2012-10-16 16:22:27,114 DEBUG org.apache.hadoop.hbase.master.RegionManager: Going to trigger a metaScan for -ROOT-
2012-10-16 16:22:27,114 DEBUG org.apache.hadoop.hbase.master.RegionManager: Going to trigger a metaScan for .META.

...

2012-10-16 16:22:28,577 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region -ROOT-,,0.70236052 to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:29,589 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region .META.,,1.1028785192 to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:30,600 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region loadtest,33333333,1349891869575.e1283ad5fe96556684fffe7d9631029b. to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:30,603 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region loadtest,66666666,1349891869575.21b97af031e2d6e1a162415d9c0e8aeb. to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:30,606 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region loadtest,22222222,1349891869575.18902646605c1c2768d8f16a45b3a1b7. to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:30,609 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region loadtest,,1349891869571.91848c59776aa07e60f416cd1eaaa5ca. to hbasedev131.ash3.facebook.com,60020,1350429747463
2012-10-16 16:22:30,612 INFO org.apache.hadoop.hbase.master.RegionManager: Assigning region loadtest,cccccccc,1349891869575.6a33bb7710b0ce6b085e0d54da3e8aa8. to hbasedev131.ash3.facebook.com,60020,1350429747463

Reviewers: kannan, mbautin

Reviewed By: mbautin

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D602655

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1399636 13f79535-47bb-0310-9956-ffa450edef68