hadoop-hdfs-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Colin Patrick McCabe (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3049) During the normal loading NN startup process, fall back on a different image or EditLog if we see one that is corrupt
Date Mon, 05 Mar 2012 21:51:57 GMT
During the normal loading NN startup process, fall back on a different image or EditLog if
we see one that is corrupt
---------------------------------------------------------------------------------------------------------------------

                 Key: HDFS-3049
                 URL: https://issues.apache.org/jira/browse/HDFS-3049
             Project: Hadoop HDFS
          Issue Type: New Feature
          Components: name-node
            Reporter: Colin Patrick McCabe
            Assignee: Colin Patrick McCabe
            Priority: Minor
             Fix For: 0.24.0


During the NameNode startup process, we load an image, and then apply edit logs to it until
we believe that we have all the latest changes.  Unfortunately, if there is an I/O error while
reading any of these files, in most cases, we simply abort the startup process.  We should
try harder to locate a readable edit log and/or image file.

*There are three main use cases for this feature:*
1. If the operating system does not honor fsync (usually due to a misconfiguration), a file
may end up in an inconsistent state.
2. In certain older releases where we did not use fallocate() or similar to pre-reserve blocks,
a disk full condition may cause a truncated log in one edit directory.
3. There may be a bug in HDFS which results in some of the data directories receiving corrupt
data, but not all.  This is the least likely use case.

*Proposed changes to normal NN startup*
* We should try a different FSImage if we can't load the first one we try.
* We should examine other FSEditLogs if we can't load the first one(s) we try.
* We should fail if we can't find EditLogs that would bring us up to what we believe is the
latest transaction ID.

Proposed changes to recovery mode NN startup:
we should list out all the available storage directories and allow the operator to select
which one he wants to use.
Something like this:
{code}
Multiple storage directories found.
1. /foo/bar
    edits__curent__XYZ          size:213421345       md5:2345345
    image                                  size:213421345       md5:2345345
2. /foo/baz
    edits__curent__XYZ          size:213421345       md5:2345345345
    image                                  size:213421345       md5:2345345
Which one would you like to use? (1/2)
{code}

As usual in recovery mode, we want to be flexible about error handling.  In this case, this
means that we should NOT fail if we can't find EditLogs that would bring us up to what we
believe is the latest transaction ID.

*Not addressed by this feature*
This feature will not address the case where an attempt to access the NameNode name directory
or directories hangs because of an I/O error.  This may happen, for example, when trying to
load an image from a hard-mounted NFS directory, when the NFS server has gone away.  Just
as now, the operator will have to notice this problem and take steps to correct it.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message