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Posted to dev@storm.apache.org by d2r <gi...@git.apache.org> on 2015/07/18 01:21:32 UTC

[GitHub] storm pull request: [STORM-139] Correctly hash byte array tuple va...

GitHub user d2r opened a pull request:

    https://github.com/apache/storm/pull/641

    [STORM-139] Correctly hash byte array tuple values

    * Unit test for correctness is included
    * The following tests showed no discernible difference in latency or throughput:
      * word_count, last 10min stats after being running > 10min
      * word_count modified to send byte[] words instead of Strings, same conditions
    
    This should handle the kinds of Objects we care about: reference types, all primitive array types, and reference array types.
    
    
    Using Java's .hashCode is a problem for distributed systems, as was pointed out in the JIRA.
    
    However, the behavior of [String#hashCode](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#hashCode%28%29), and the implementation of [java.util.Arrays#hashCode](http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/Arrays.java#Arrays.hashCode%28float[]%29) for all primitive array types is defined and should be consistent across JVMs.  This leaves Objects and Object[] that are not Strings.  In these cases, this change still trusts the hashCode method provided in those classes.
    
    In practice, bad cases should be rare.  In the cases when hashing is inconsistent and some sort of partitioning is used, it could be very difficult to debug.
    


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/d2r/storm storm-138-byte-array-hashcode

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/storm/pull/641.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #641
    
----
commit 46b8c9e71b4b9b3f0e8c762fe070793e3f6d4971
Author: Derek Dagit <de...@yahoo-inc.com>
Date:   2015-07-17T21:54:32Z

    Correctly hash byte array tuple values

----


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[GitHub] storm pull request: [STORM-139] Correctly hash byte array tuple va...

Posted by HeartSaVioR <gi...@git.apache.org>.

Github user HeartSaVioR commented on a diff in the pull request:

    https://github.com/apache/storm/pull/641#discussion_r35121430
  
    --- Diff: storm-core/src/jvm/backtype/storm/grouping/PartialKeyGrouping.java ---
    @@ -65,7 +66,11 @@ public void prepare(WorkerTopologyContext context, GlobalStreamId stream, List<I
                     List<Object> selectedFields = outFields.select(fields, values);
                     ByteBuffer out = ByteBuffer.allocate(selectedFields.size() * 4);
                     for (Object o: selectedFields) {
    -                    out.putInt(o.hashCode());
    +                    if (o instanceof Object[]) {
    --- End diff --
    
    @d2r 
    I didn't think about primitive array type.
    Actually I mean that,
    - Does 'o' have an chance to be instance of List? 
    - If then, could we apply ```((List)o).toArray()``` to convert it Object[], and let if statement handle it?


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[GitHub] storm pull request: [STORM-139] Correctly hash byte array tuple va...

Posted by vesense <gi...@git.apache.org>.

Github user vesense commented on the pull request:

    https://github.com/apache/storm/pull/641#issuecomment-123242642
  
    +1


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[GitHub] storm pull request: [STORM-139] Correctly hash byte array tuple va...

Posted by HeartSaVioR <gi...@git.apache.org>.

Github user HeartSaVioR commented on a diff in the pull request:

    https://github.com/apache/storm/pull/641#discussion_r35109156
  
    --- Diff: storm-core/src/jvm/backtype/storm/grouping/PartialKeyGrouping.java ---
    @@ -65,7 +66,11 @@ public void prepare(WorkerTopologyContext context, GlobalStreamId stream, List<I
                     List<Object> selectedFields = outFields.select(fields, values);
                     ByteBuffer out = ByteBuffer.allocate(selectedFields.size() * 4);
                     for (Object o: selectedFields) {
    -                    out.putInt(o.hashCode());
    +                    if (o instanceof Object[]) {
    --- End diff --
    
    @d2r 
    Could we add same thing (converting List to Object[] by toArray, and apply Arrays.deepHashCode()) from list-hash-code to this?


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[GitHub] storm pull request: [STORM-139] Correctly hash byte array tuple va...

Posted by HeartSaVioR <gi...@git.apache.org>.

Github user HeartSaVioR commented on the pull request:

    https://github.com/apache/storm/pull/641#issuecomment-123884557
  
    LGTM, +1.


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