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https://issues.apache.org/jira/browse/HDFS-1257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881893#action_12881893
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Ramkumar Vadali commented on HDFS-1257:
---------------------------------------
My proposal is to wrap FSNamesystem#recentInvalidateSets in
Collections.synchronizedMap(). That should fix this problem.
--- a/src/hdfs/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
+++ b/src/hdfs/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
@@ -189,7 +189,7 @@ public class FSNamesystem implements FSConstants,
FSNamesystemMBean, FSClusterSt
// Mapping: StorageID -> ArrayList<Block>
//
private Map<String, Collection<Block>> recentInvalidateSets =
- new TreeMap<String, Collection<Block>>();
+ Collections.synchronizedMap(new TreeMap<String, Collection<Block>>());
//
// Keeps a TreeSet for every named node. Each treeset contains
> Race condition introduced by HADOOP-5124
> ----------------------------------------
>
> Key: HDFS-1257
> URL: https://issues.apache.org/jira/browse/HDFS-1257
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: Ramkumar Vadali
>
> HADOOP-5124 provided some improvements to FSNamesystem#recentInvalidateSets.
> But it introduced unprotected access to the data structure
> recentInvalidateSets. Specifically, FSNamesystem.computeInvalidateWork
> accesses recentInvalidateSets without read-lock protection. If there is
> concurrent activity (like reducing replication on a file) that adds to
> recentInvalidateSets, the name-node crashes with a
> ConcurrentModificationException.
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