[HADOOP-1471] seekToNewSource() might not work correctly with Checksum failures.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 0.12.3
• Assignee: Unassigned
• Reporter: Raghu Angadi
• Created: 06/Jun/07 21:02
• Updated: 08/Jul/09 16:42
• Resolved: 18/Jul/07 18:17

Description

Patch submitted to HADOOP-893 (by me ) seemhave a bug in how it deals with the set deadNodes. After the patch, the seekToNewSource() looks like this :

    public synchronized boolean seekToNewSource(long targetPos) throws IOException {
      boolean markedDead = deadNodes.contains(currentNode);
      deadNodes.add(currentNode);
      DatanodeInfo oldNode = currentNode;
      DatanodeInfo newNode = blockSeekTo(targetPos);
      if (!markedDead) {
        /* remove it from deadNodes. blockSeekTo could have cleared 
         * deadNodes and added currentNode again. Thats ok. */
        deadNodes.remove(oldNode);
      }
      // ...

I guess with the expectation that caller of this function decides before the call whether to put the node in deadNodes or not. I am not sure whether this was a bug then or not but it certainly seems to be bug now. i.e. when there is a checksum error with replica1, we try replica2 and if there a checksum error again, then we try replica1 again!

Note that ChecksumFileSystem.java was created after HADOOP-893 was resolved.

Issue Links

• is part of: HADOOP-1134 Block level CRCs in HDFS