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https://issues.apache.org/jira/browse/HBASE-8374?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ted Yu updated HBASE-8374:
--------------------------
Attachment: 8374-trunk-v4.txt
w.r.t. Nicolas' question, I think what happened was that serversToIndex map
wasn't fully populated because one loop was used to iterate through
clusterState.entrySet().
In patch v4, I introduced another loop to populate serversToIndex map.
I kept the checking from patch v3 in case regionFinder.getTopBlockLocations()
returns some ServerName which is not in serversToIndex map.
> NPE when launching the balance
> ------------------------------
>
> Key: HBASE-8374
> URL: https://issues.apache.org/jira/browse/HBASE-8374
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Affects Versions: 0.95.0
> Environment: AWS / real cluster with 3 nodes + master
> Reporter: Nicolas Liochon
> Assignee: Ted Yu
> Fix For: 0.98.0, 0.95.1
>
> Attachments: 8374-trunk.txt, 8374-trunk-v2.txt, 8374-trunk-v3.txt,
> 8374-trunk-v4.txt
>
>
> I don't reproduce this all the time, but I had it on a fairly clean env.
> It occurs every 5 minutes (i.e. the balancer period). Impact is severe: the
> balancer does not run. When it starts to occurs, it occurs all the time. I
> haven't tried to restart the master, but I think it should be enough.
> Now, looking at the code, the NPE is strange.
> {noformat}
> 2013-04-18 08:09:52,079 ERROR [box,60000,1366281581983-BalancerChore]
> org.apache.hadoop.hbase.master.balancer.BalancerChore: Caught exception
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer$Cluster.<init>(BaseLoadBalancer.java:145)
> at
> org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer.balanceCluster(StochasticLoadBalancer.java:194)
> at org.apache.hadoop.hbase.master.HMaster.balance(HMaster.java:1295)
> at
> org.apache.hadoop.hbase.master.balancer.BalancerChore.chore(BalancerChore.java:48)
> at org.apache.hadoop.hbase.Chore.run(Chore.java:81)
> at java.lang.Thread.run(Thread.java:662)
> 2013-04-18 08:09:52,103 DEBUG [box,60000,1366281581983-CatalogJanitor]
> org.apache.hadoop.hbase.client.ClientScanner: Creating scanner over .META.
> starting at key ''
> {noformat}
> {code}
> if (regionFinder != null) {
> //region location
> List<ServerName> loc = regionFinder.getTopBlockLocations(region);
> regionLocations[regionIndex] = new int[loc.size()];
> for (int i=0; i < loc.size(); i++) {
> regionLocations[regionIndex][i] =
> serversToIndex.get(loc.get(i)); // <========= NPE here
> }
> }
> {code}
> pinging [~enis], just in case.
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