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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14535) wasb: support for random access and seek of block blobs
Date Tue, 11 Jul 2017 11:41:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16082089#comment-16082089
] 

Steve Loughran commented on HADOOP-14535:
-----------------------------------------

Full test run completed.

{code}

Results :

Tests run: 694, Failures: 0, Errors: 0, Skipped: 121
{code}

I will note that test run performance awful, even worse with this, and one run timed out.
After this patch is in, I'm not going to approve anything else until HADOOP-14553 has the
test process under control. Sorry


> wasb: support for random access and seek of block blobs
> -------------------------------------------------------
>
>                 Key: HADOOP-14535
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14535
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs/azure
>            Reporter: Thomas
>            Assignee: Thomas
>         Attachments: 0001-Random-access-and-seek-imporvements-to-azure-file-system.patch,
0003-Random-access-and-seek-imporvements-to-azure-file-system.patch, 0004-Random-access-and-seek-imporvements-to-azure-file-system.patch,
0005-Random-access-and-seek-imporvements-to-azure-file-system.patch, HADOOP-14535-006.patch
>
>
> This change adds a seek-able stream for reading block blobs to the wasb:// file system.
> If seek() is not used or if only forward seek() is used, the behavior of read() is unchanged.
> That is, the stream is optimized for sequential reads by reading chunks (over the network)
in
> the size specified by "fs.azure.read.request.size" (default is 4 megabytes).
> If reverse seek() is used, the behavior of read() changes in favor of reading the actual
number
> of bytes requested in the call to read(), with some constraints.  If the size requested
is smaller
> than 16 kilobytes and cannot be satisfied by the internal buffer, the network read will
be 16
> kilobytes.  If the size requested is greater than 4 megabytes, it will be satisfied by
sequential
> 4 megabyte reads over the network.
> This change improves the performance of FSInputStream.seek() by not closing and re-opening
the
> stream, which for block blobs also involves a network operation to read the blob metadata.
Now
> NativeAzureFsInputStream.seek() checks if the stream is seek-able and moves the read
position.
> [^attachment-name.zip]



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