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https://issues.apache.org/jira/browse/HADOOP-11867?focusedWorklogId=657692&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-657692
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ASF GitHub Bot logged work on HADOOP-11867:
-------------------------------------------

                Author: ASF GitHub Bot
            Created on: 30/Sep/21 00:15
            Start Date: 30/Sep/21 00:15
    Worklog Time Spent: 10m 
      Work Description: mukund-thakur opened a new pull request #3499:
URL: https://github.com/apache/hadoop/pull/3499


   Rebased work on top of https://github.com/apache/hadoop/pull/1830 
   
   Conflicts:
        
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/BufferedFSInputStream.java
        
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/ChecksumFileSystem.java
        
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataInputStream.java
        
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/RawLocalFileSystem.java
        pom.xml
   
   
   
   ### Description of PR
   Adding support for multiple ranged read async api in PositionedReadable. The 
default iterates through the ranges to read each synchronously, but the intent 
is that FSDataInputStream subclasses can make more efficient readers especially 
object stores implementation.
   
   ### How was this patch tested?
   Re ran the benchmarks for now. There are already some UT's present in this 
patch. Thinking of how can I write contract tests. 
   
   ### For code changes:
   
   - [ ] Does the title or this PR starts with the corresponding JIRA issue id 
(e.g. 'HADOOP-17799. Your PR title ...')?
   - [ ] Object storage: have the integration tests been executed and the 
endpoint declared according to the connector-specific documentation?
   - [ ] If adding new dependencies to the code, are these dependencies 
licensed in a way that is compatible for inclusion under [ASF 
2.0](http://www.apache.org/legal/resolved.html#category-a)?
   - [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`, 
`NOTICE-binary` files?
   
   


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 657692)
    Time Spent: 7.5h  (was: 7h 20m)

> FS API: Add a high-performance vectored Read to FSDataInputStream API
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-11867
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11867
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs, fs/azure, fs/s3, hdfs-client
>    Affects Versions: 3.0.0
>            Reporter: Gopal Vijayaraghavan
>            Assignee: Owen O'Malley
>            Priority: Major
>              Labels: performance, pull-request-available
>          Time Spent: 7.5h
>  Remaining Estimate: 0h
>
> The most significant way to read from a filesystem in an efficient way is to 
> let the FileSystem implementation handle the seek behaviour underneath the 
> API to be the most efficient as possible.
> A better approach to the seek problem is to provide a sequence of read 
> locations as part of a single call, while letting the system schedule/plan 
> the reads ahead of time.
> This is exceedingly useful for seek-heavy readers on HDFS, since this allows 
> for potentially optimizing away the seek-gaps within the FSDataInputStream 
> implementation.
> For seek+read systems with even more latency than locally-attached disks, 
> something like a {{readFully(long[] offsets, ByteBuffer[] chunks)}} would 
> take of the seeks internally while reading chunk.remaining() bytes into each 
> chunk (which may be {{slice()}}ed off a bigger buffer).
> The base implementation can stub in this as a sequence of seeks + read() into 
> ByteBuffers, without forcing each FS implementation to override this in any 
> way.



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