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From "Jonathan Eagles (JIRA)" <j...@apache.org>
Subject [jira] [Created] (TEZ-3685) ShuffleHandler completedInputSet off-by-one error
Date Thu, 06 Apr 2017 19:56:44 GMT
Jonathan Eagles created TEZ-3685:
------------------------------------

             Summary: ShuffleHandler completedInputSet off-by-one error
                 Key: TEZ-3685
                 URL: https://issues.apache.org/jira/browse/TEZ-3685
             Project: Apache Tez
          Issue Type: Sub-task
            Reporter: Jonathan Eagles
            Assignee: Jonathan Eagles


Per comment in TEZ-3334 https://issues.apache.org/jira/browse/TEZ-3334?focusedCommentId=15950550&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15950550

Addressing The off by 1 issue / other correctness issues in this jira
- ShuffleManager: has moved to using a BitSet instead of a ConcurrentSet. May need to look
at the synchronization points required for the bitset. (access to the map had some synchronized
and some non synchronized access)
- In optimizeLocalFetch - report success only after an entire source is done (i.e. all partitions
for it). Otherwise the same input may be reported multiple times, which could be problematic.
- Why was this removed?
{code}
-    // Sanity check
-    // we are guaranteed that key is not null
-    if (srcAttemptsRemaining.get(srcAttemptId.toString()) == null) {
-      // wrongMapErrs.increment(1);
-      LOG.warn("Invalid input. Received output for headerPathComponent: "
-          + pathComponent + "nextRemainingSrcAttemptId: "
-          + getNextRemainingAttempt() + ", mappedSrcAttemptId: " + srcAttemptId);
-      return false;
-    }
{code}
- 
Is there an off by 1 error here? Specifically. input.getInputIdentifier() + ((CompositeInputAttemptIdentifier)
input).getInputIdentifierCount(). Think getInputIdentifierCount is always at least 1.
{code}
+      if(input instanceof CompositeInputAttemptIdentifier) {
+        // LLL Is there an off by 0 case here. i.e. getInputIdentiferCount will be set to
1 for a regular event.
+        // We start scanning the bitst early. Also depends on how completedInputSet is setup.
+        if (completedInputSet.nextClearBit(input.getInputIdentifier()) >=
+            input.getInputIdentifier() + ((CompositeInputAttemptIdentifier) input).getInputIdentifierCount())
{
+          inputIter.remove();
+          continue;
+        }
+      } else {
+        if (completedInputSet.get(input.getInputIdentifier())) {
+          inputIter.remove();
+          continue;
+        }
{code}



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