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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2840) Should using `System.nanoTime() ^ this.hashCode()` for StaticHostProvider
Date Tue, 29 Aug 2017 13:31:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16145292#comment-16145292
] 

ASF GitHub Bot commented on ZOOKEEPER-2840:
-------------------------------------------

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

    https://github.com/apache/zookeeper/pull/303#discussion_r135789082
  
    --- Diff: src/java/main/org/apache/zookeeper/client/StaticHostProvider.java ---
    @@ -71,7 +71,7 @@
          *             if serverAddresses is empty or resolves to an empty list
          */
         public StaticHostProvider(Collection<InetSocketAddress> serverAddresses) {
    -       sourceOfRandomness = new Random(System.currentTimeMillis() ^ this.hashCode());
    +       sourceOfRandomness = new Random(System.nanoTime() ^ this.hashCode());
    --- End diff --
    
    @asdf2014 
    - shift right a space(haha,original code is also not alignment)
    - according to [ZOOKEEPER-1990](https://issues.apache.org/jira/browse/ZOOKEEPER-1990)
       >    the goal here is to make sure that when multiple client threads start at the
same time on the same machine 
             (such as in our systest) and execute this line each one is likely to have a different
random seed.
    - your demo is not convincing because different client have different values of `this.hashCode()`(different
instances) although the elements in inetSocketAddressesList is same. Look at my [demo](https://github.com/maoling/fuck_zookeeper/blob/master/src/java/test/com/apache/zookeeper/self/ZOOKEEPER_2840.java)


> Should using `System.nanoTime() ^ this.hashCode()` for StaticHostProvider
> -------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2840
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2840
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: java client
>    Affects Versions: 3.5.3
>            Reporter: Benedict Jin
>            Assignee: Benedict Jin
>             Fix For: 3.5.4
>
>   Original Estimate: 72h
>  Remaining Estimate: 72h
>
> Should using `System.nanoTime() ^ this.hashCode()` for StaticHostProvider instead of
`System.currentTimeMillis()`. Because if we have three Zookeeper server nodes and set the
`zookeeper.leaderServes` as `no`, then those connections from client will always connect with
the first Zookeeper server node. Due to...
> ```java
>     @Test
>     public void testShuffle() throws Exception {
>         LinkedList<InetSocketAddress> inetSocketAddressesList = new LinkedList<>();
>         inetSocketAddressesList.add(new InetSocketAddress(0));
>         inetSocketAddressesList.add(new InetSocketAddress(1));
>         inetSocketAddressesList.add(new InetSocketAddress(2));
>         /*
>         1442045361
>         currentTime: 1499253530044, currentTime ^ hashCode: 1500143845389, Result: 1
2 0
>         currentTime: 1499253530044, currentTime ^ hashCode: 1500143845389, Result: 2
0 1
>         currentTime: 1499253530045, currentTime ^ hashCode: 1500143845388, Result: 0
1 2
>         currentTime: 1499253530045, currentTime ^ hashCode: 1500143845388, Result: 1
2 0
>         currentTime: 1499253530046, currentTime ^ hashCode: 1500143845391, Result: 1
2 0
>         currentTime: 1499253530046, currentTime ^ hashCode: 1500143845391, Result: 1
2 0
>         currentTime: 1499253530046, currentTime ^ hashCode: 1500143845391, Result: 1
2 0
>         currentTime: 1499253530046, currentTime ^ hashCode: 1500143845391, Result: 1
2 0
>         currentTime: 1499253530047, currentTime ^ hashCode: 1500143845390, Result: 1
2 0
>         currentTime: 1499253530047, currentTime ^ hashCode: 1500143845390, Result: 1
2 0
>          */
>         internalShuffleMillis(inetSocketAddressesList);
>         /*
>         146611050
>         currentTime: 22618159623770, currentTime ^ hashCode: 22618302559536, Result:
2 1 0
>         currentTime: 22618159800738, currentTime ^ hashCode: 22618302085832, Result:
0 1 2
>         currentTime: 22618159967442, currentTime ^ hashCode: 22618302248888, Result:
1 0 2
>         currentTime: 22618160135080, currentTime ^ hashCode: 22618302013634, Result:
2 1 0
>         currentTime: 22618160302095, currentTime ^ hashCode: 22618301535077, Result:
2 1 0
>         currentTime: 22618160490260, currentTime ^ hashCode: 22618301725822, Result:
1 0 2
>         currentTime: 22618161566373, currentTime ^ hashCode: 22618300303823, Result:
1 0 2
>         currentTime: 22618161745518, currentTime ^ hashCode: 22618300355844, Result:
2 1 0
>         currentTime: 22618161910357, currentTime ^ hashCode: 22618291603775, Result:
2 1 0
>         currentTime: 22618162079549, currentTime ^ hashCode: 22618291387479, Result:
0 1 2
>          */
>         internalShuffleNano(inetSocketAddressesList);
>         inetSocketAddressesList.clear();
>         inetSocketAddressesList.add(new InetSocketAddress(0));
>         inetSocketAddressesList.add(new InetSocketAddress(1));
>         /*
>         415138788
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530050, currentTime ^ hashCode: 1499124456998, Result: 0
1
>         currentTime: 1499253530053, currentTime ^ hashCode: 1499124456993, Result: 0
1
>         currentTime: 1499253530055, currentTime ^ hashCode: 1499124456995, Result: 0
1
>         currentTime: 1499253530055, currentTime ^ hashCode: 1499124456995, Result: 0
1
>         currentTime: 1499253530055, currentTime ^ hashCode: 1499124456995, Result: 0
1
>          */
>         internalShuffleMillis(inetSocketAddressesList);
>         /*
>         13326370
>         currentTime: 22618168292396, currentTime ^ hashCode: 22618156149774, Result:
1 0
>         currentTime: 22618168416181, currentTime ^ hashCode: 22618156535703, Result:
1 0
>         currentTime: 22618168534056, currentTime ^ hashCode: 22618156432394, Result:
0 1
>         currentTime: 22618168666548, currentTime ^ hashCode: 22618155774358, Result:
0 1
>         currentTime: 22618168818946, currentTime ^ hashCode: 22618155623712, Result:
0 1
>         currentTime: 22618168936821, currentTime ^ hashCode: 22618156011863, Result:
1 0
>         currentTime: 22618169056251, currentTime ^ hashCode: 22618155893721, Result:
1 0
>         currentTime: 22618169611103, currentTime ^ hashCode: 22618157370237, Result:
1 0
>         currentTime: 22618169744528, currentTime ^ hashCode: 22618156713138, Result:
1 0
>         currentTime: 22618171273170, currentTime ^ hashCode: 22618184562672, Result:
1 0
>          */
>         internalShuffleNano(inetSocketAddressesList);
>     }
>     private void internalShuffleMillis(LinkedList<InetSocketAddress> inetSocketAddressesList)
throws Exception {
>         int hashCode = new StaticHostProvider(inetSocketAddressesList).hashCode();
>         System.out.println(hashCode);
>         int count = 10;
>         Random r;
>         while (count > 0) {
>             long currentTime = System.currentTimeMillis();
>             r = new Random(currentTime ^ hashCode);
>             System.out.print(String.format("currentTime: %s, currentTime ^ hashCode:
%s, Result: ",
>                     currentTime, currentTime ^ hashCode));
>             Collections.shuffle(inetSocketAddressesList, r);
>             for (InetSocketAddress inetSocketAddress : inetSocketAddressesList) {
>                 System.out.print(String.format("%s ", inetSocketAddress.getPort()));
>             }
>             System.out.println();
>             count--;
>         }
>     }
>     private void internalShuffleNano(LinkedList<InetSocketAddress> inetSocketAddressesList)
throws Exception {
>         int hashCode = new StaticHostProvider(inetSocketAddressesList).hashCode();
>         System.out.println(hashCode);
>         int count = 10;
>         Random r;
>         while (count > 0) {
>             long currentTime = System.nanoTime();
>             r = new Random(currentTime ^ hashCode);
>             System.out.print(String.format("currentTime: %s, currentTime ^ hashCode:
%s, Result: ",
>                     currentTime, currentTime ^ hashCode));
>             Collections.shuffle(inetSocketAddressesList, r);
>             for (InetSocketAddress inetSocketAddress : inetSocketAddressesList) {
>                 System.out.print(String.format("%s ", inetSocketAddress.getPort()));
>             }
>             System.out.println();
>             count--;
>         }
>     }
> ```



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