[jira] [Updated] (HADOOP-14478) Optimize NativeAzureFsInputStream for positional reads

["Rajesh Balamohan (JIRA)" <ji...@apache.org>]

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

Rajesh Balamohan updated HADOOP-14478:
--------------------------------------
    Attachment: HADOOP-14478.001.patch

Attaching .1 patch for review. This includes changes related to HADOOP-14473 as well.

> 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
>         Attachments: HADOOP-14478.001.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 apart of this JIRA.



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