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From "Mingliang Liu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-14478) Optimize NativeAzureFsInputStream for positional reads
Date Mon, 05 Jun 2017 23:06:12 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-14478?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Mingliang Liu updated HADOOP-14478:
       Resolution: Fixed
     Hadoop Flags: Reviewed
    Fix Version/s: 3.0.0-alpha4
           Status: Resolved  (was: Patch Available)

Committed to {{branch-2}} and {{trunk}} branches. Thanks for your contribution, [~rajesh.balamohan].
Thanks for your review [~stevel@apache.org].

> Optimize NativeAzureFsInputStream for positional reads
> ------------------------------------------------------
>                 Key: HADOOP-14478
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14478
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs/azure
>            Reporter: Rajesh Balamohan
>            Assignee: Rajesh Balamohan
>             Fix For: 2.9.0, 3.0.0-alpha4
>         Attachments: HADOOP-14478.001.patch, HADOOP-14478.002.patch, HADOOP-14478.003.patch
> Azure's {{BlobbInputStream}} internally buffers 4 MB of data irrespective of the data
length requested for. This would be beneficial for sequential reads. However, for positional
reads (seek to specific location, read x number of bytes, seek back to original location)
this may not be beneficial and might even download lot more data which are not used later.
> It would be good to override {{readFully(long position, byte[] buffer, int offset, int
length)}} for {{NativeAzureFsInputStream}} and make use of {{mark(readLimit)}} as a hint to
Azure's BlobInputStream.
> BlobInputStream reference: https://github.com/Azure/azure-storage-java/blob/master/microsoft-azure-storage/src/com/microsoft/azure/storage/blob/BlobInputStream.java#L448
> BlobInputStream can consider this as a hint later to determine the amount of data to
be read ahead. Changes to BlobInputStream would not be addressed in this JIRA.

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