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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2602) Standby needs to maintain BlockInfo while following edits
Date Thu, 15 Dec 2011 10:28:30 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13170108#comment-13170108
] 

Todd Lipcon commented on HDFS-2602:
-----------------------------------

bq. I just don't understand why this block persisting issue keeps migrating from HDFS-978
to HDFS-1108 and now here? Are you seriously measuring performance in # of jiras (or lines
of code).
Funny :)

Dhruba opened both HDFS-978 and HDFS-1108, not sure why. It ended up migrating here because
at first we considered it separate, and were building this patch on top of HDFS-1108. Then
by the time the patch was done it seemed to make more sense to integrate them. Would be reasonable
to commit them separately, though - 1108 for the logging and this one for the FSEditLog changes
to avoid losing the block locations. Would you prefer that or can we just commit this as is
once it's reviewed?
                
> Standby needs to maintain BlockInfo while following edits
> ---------------------------------------------------------
>
>                 Key: HDFS-2602
>                 URL: https://issues.apache.org/jira/browse/HDFS-2602
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha
>    Affects Versions: HA branch (HDFS-1623)
>            Reporter: Todd Lipcon
>            Assignee: Aaron T. Myers
>            Priority: Critical
>         Attachments: HDFS-2602.patch, HDFS-2602.patch, HDFS-2602.patch
>
>
> As described in HDFS-1975:
> When we close a file, or add another block to a file, we write OP_CLOSE or OP_ADD in
the txn log. FSEditLogLoader, when it sees these types of transactions, creates new BlockInfo
objects for all of the blocks listed in the transaction. These new BlockInfos have no block
locations associated. So, when we close a file, the SBNN loses its block locations info for
that file and is no longer "hot".
> I have an ugly hack which copies over the old BlockInfos from the existing INode, but
I'm not convinced it's the right way. It might be cleaner to add new opcode types like OP_ADD_ADDITIONAL_BLOCK,
and actually treat OP_CLOSE as just a finalization of INodeFileUnderConstruction to INodeFile,
rather than replacing block info at all.

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