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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Work logged] (HDDS-1496) Support partial chunk reads and checksum verification
Date Thu, 06 Jun 2019 20:47:00 GMT

     [ https://issues.apache.org/jira/browse/HDDS-1496?focusedWorklogId=255423&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-255423

ASF GitHub Bot logged work on HDDS-1496:

                Author: ASF GitHub Bot
            Created on: 06/Jun/19 20:46
            Start Date: 06/Jun/19 20:46
    Worklog Time Spent: 10m 
      Work Description: hanishakoneru commented on pull request #804: HDDS-1496. Support partial
chunk reads and checksum verification
URL: https://github.com/apache/hadoop/pull/804#discussion_r291364624

 File path: hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/BlockInputStream.java
 @@ -115,8 +116,13 @@ public BlockInputStream(BlockID blockId, long blockLen, Pipeline pipeline,
   public synchronized void initialize() throws IOException {
-    List<ChunkInfo> chunks = getChunkInfos();
+    // Pre-check that the stream has not been intialized already
+    if (initialized) {
+      return;
+    }
+    Preconditions.checkArgument(chunkOffsets == null);
 Review comment:
   Just extra precaution so that if new methods are implemented then the stream is not initialized
twice. It is not necessary for now though. Removed it.
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Issue Time Tracking

    Worklog Id:     (was: 255423)
    Time Spent: 9.5h  (was: 9h 20m)

> Support partial chunk reads and checksum verification
> -----------------------------------------------------
>                 Key: HDDS-1496
>                 URL: https://issues.apache.org/jira/browse/HDDS-1496
>             Project: Hadoop Distributed Data Store
>          Issue Type: Improvement
>            Reporter: Hanisha Koneru
>            Assignee: Hanisha Koneru
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 9.5h
>  Remaining Estimate: 0h
> BlockInputStream#readChunkFromContainer() reads the whole chunk from disk even if we
need to read only a part of the chunk.
> This Jira aims to improve readChunkFromContainer so that only that part of the chunk
file is read which is needed by client plus the part of chunk file which is required to verify
the checksum.
> For example, lets say the client is reading from index 120 to 450 in the chunk. And let's
say checksum is stored for every 100 bytes in the chunk i.e. the first checksum is for bytes
from index 0 to 99, the next for bytes from index 100 to 199 and so on. To verify bytes from
120 to 450, we would need to read from bytes 100 to 499 so that checksum verification can
be done.

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