Apache9 commented on a change in pull request #2497:
URL: https://github.com/apache/hbase/pull/2497#discussion_r501539893
##########
File path:
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignmentManager.java
##########
@@ -870,32 +870,49 @@ public TransitRegionStateProcedure
createOneUnassignProcedure(RegionInfo ri, boo
.sorted(AssignmentManager::compare).toArray(TransitRegionStateProcedure[]::new);
}
+ // for creating unassign TRSP when disabling a table or closing excess
region replicas
+ private TransitRegionStateProcedure
forceCreateUnssignProcedure(RegionStateNode regionNode) {
+ regionNode.lock();
+ try {
+ if (!regionStates.include(regionNode, false) ||
+ regionStates.isRegionOffline(regionNode.getRegionInfo())) {
+ return null;
+ }
+ // As in DisableTableProcedure or ModifyTableProcedure, we will hold the
xlock for table, so
+ // we can make sure that this procedure has not been executed yet, as
TRSP will hold the
+ // shared lock for table all the time. So here we will unset it and when
it is actually
+ // executed, it will find that the attach procedure is not itself and
quit immediately.
+ if (regionNode.getProcedure() != null) {
Review comment:
This is a fencing mechanism to prevent double assign. We have a
procedure field for every region node, before scheduling a new TRSP for a
region, we should attach the TRSP to this field, if there is already one, we
will fail immediately.
And here, the trick is the locking for procedures, for ModifyTableProcedure
and DisableTableProcedure, we will hold the exclusive lock on the table, while
for a TRSP, we will hold the shared lock on the table. Both locks will be held
through the whole life cycle of the procedure, so here, since we hae already
held the exclusive lock on the table, we can make sure that, even if there is
already a TRSP attached, it has not been executed yet, so it is safe to
'abandon' and attach a new TRSP to close it. The actual 'abandon' is done in
the execute method in TRSP, it will check whether it is still the one attached,
if not, it will quit immediately.
##########
File path:
hbase-protocol-shaded/src/main/protobuf/server/master/MasterProcedure.proto
##########
@@ -72,6 +72,8 @@ enum ModifyTableState {
MODIFY_TABLE_DELETE_FS_LAYOUT = 5;
MODIFY_TABLE_POST_OPERATION = 6;
MODIFY_TABLE_REOPEN_ALL_REGIONS = 7;
+ MODIFY_TABLE_CLOSE_EXCESS_REPLICAS = 8;
+ MODIFY_TABLE_ASSIGN_NEW_REPLICAS = 9;
Review comment:
Yes.
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