hadoop-hdfs-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-5438) Flaws in block report processing can cause data loss
Date Mon, 28 Oct 2013 20:41:35 GMT
Kihwal Lee created HDFS-5438:
--------------------------------

             Summary: Flaws in block report processing can cause data loss
                 Key: HDFS-5438
                 URL: https://issues.apache.org/jira/browse/HDFS-5438
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.2.0, 0.23.9
            Reporter: Kihwal Lee
            Priority: Critical


The incremental block reports from data nodes and block commits are asynchronous. This becomes
troublesome when the gen stamp for a block is changed during a write pipeline recovery.

* If an incremental block report is delayed from a node but NN had enough replicas already,
a report with the old gen stamp may be received after block completion. This replica will
be correctly marked corrupt. But if the node had participated in the pipeline recovery, a
new (delayed) report with the correct gen stamp will come soon. However, this report won't
have any effect on the corrupt state of the replica.

* If block reports are received while the block is still under construction (i.e. client's
call to make block committed has not been received by NN), they are blindly accepted regardless
of the gen stamp. If a failed node reports in with the old gen stamp while pipeline recovery
is on-going, it will be accepted and counted as valid during commit of the block.

Due to the above two problems, correct replicas can be marked corrupt and corrupt replicas
can be accepted during commit.  So far we have observed two cases in production.

* The client hangs forever to close a file. All replicas are marked corrupt.
* After the successful close of a file, read fails. Corrupt replicas are accepted them during
commit and valid replicas are marked corrupt afterward.




--
This message was sent by Atlassian JIRA
(v6.1#6144)

Mime
View raw message