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From "Rushabh S Shah (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10348) Namenode report bad block method doesn't check whether the block belongs to datanode before adding it to corrupt replicas map.
Date Fri, 29 Apr 2016 19:19:12 GMT
Rushabh S Shah created HDFS-10348:

             Summary: Namenode report bad block method doesn't check whether the block belongs
to datanode before adding it to corrupt replicas map.
                 Key: HDFS-10348
                 URL: https://issues.apache.org/jira/browse/HDFS-10348
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.7.0
            Reporter: Rushabh S Shah
            Assignee: Rushabh S Shah

Namenode (via report bad block nethod) doesn't check whether the block belongs to the datanode
before it adds to corrupt replicas map.
In one of our cluster we found that there were 3 lingering corrupt blocks.
It happened in the following order.
1. Two clients called getBlockLocations for a particular file.
2. Client C1 tried to open the file and encountered checksum error from   node N3 and it reported
bad block (blk1) to the namenode.
3. Namenode added that node N3 and block blk1  to corrrupt replicas map   and ask one of the
good node (one of the 2 nodes) to replicate the block to another node N4.
4. After receiving the block, N4 sends an IBR (with RECEIVED_BLOCK) to namenode.
5. Namenode removed the block and node N3 from corrupt replicas map.
   It also removed N3's storage from triplets and queued an invalidate request for N3.
6. In the mean time, Client C2 tries to open the file and the request went to node N3.
   C2 also encountered the checksum exception and reported bad block to namenode.
7. Namenode added the corrupt block blk1 and node N3 to the corrupt replicas map without confirming
whether node N3 has the block or not.

After deleting the block, N3 sends an IBR (with DELETED) and the namenode simply ignores the
report since the N3's storage is no longer in the triplets(from step 5)

We took the node out of rotation, but still the block was present only in the corruptReplciasMap.

Since on removing the node, we only goes through the block which are present in the triplets
for a given datanode.

Kuhu's patch fixed this bug via https://issues.apache.org/jira/browse/HDFS-9958.
But I think the following check should be made in the BlockManager#markBlockAsCorrupt instead
of BlockManager#findAndMarkBlockAsCorrupt.
if (storage == null) {
      storage = storedBlock.findStorageInfo(node);

    if (storage == null) {
      blockLog.debug("BLOCK* findAndMarkBlockAsCorrupt: {} not found on {}",
          blk, dn);

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