cuijianwei created HBASE-12760:
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Summary: Return NullAction when region is located in highest
locality server
Key: HBASE-12760
URL: https://issues.apache.org/jira/browse/HBASE-12760
Project: HBase
Issue Type: Improvement
Components: Balancer
Affects Versions: 0.99.2
Reporter: cuijianwei
Priority: Minor
StochasticLoadBalancer#LocalityBasedCandidateGenerator will try to move a
region to the server with the highest locality. The target server is selected
by LocalityBasedCandidateGenerator.pickHighestLocalityServer, as:
{code}
private int pickHighestLocalityServer(Cluster cluster, int thisServer, int
thisRegion) {
...
for (int loc : regionLocations) {
if (loc >= 0 && loc != thisServer) { // find the first suitable server
return loc;
}
}
...
}
{code}
If the region is just located in the best server, the current logic will choose
the server having the second highest locality, generating an action to try to
move region to server with lower locality. Is it better to return a NullAction
in this situation (as below)? so that there won't be further computing caused
by the generated action.
{code}
private int pickHighestLocalityServer(Cluster cluster, int thisServer, int
thisRegion) {
...
for (int loc : regionLocations) {
if (loc == thisServer) {
return -1; // return NullAction when the region is just located in
the best server
}
if (loc >= 0) { // find the first suitable server
return loc;
}
}
...
}
{code}
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