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From "Mark Miller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-8849) ChaosMonkey should cuase chaos in a more reproducible manner
Date Mon, 14 Mar 2016 23:37:33 GMT

    [ https://issues.apache.org/jira/browse/SOLR-8849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15194395#comment-15194395
] 

Mark Miller commented on SOLR-8849:
-----------------------------------

Makes sense to me. I don't see a problem with the change. 

> ChaosMonkey should cuase chaos in a more reproducible manner
> ------------------------------------------------------------
>
>                 Key: SOLR-8849
>                 URL: https://issues.apache.org/jira/browse/SOLR-8849
>             Project: Solr
>          Issue Type: Test
>            Reporter: Hoss Man
>            Assignee: Hoss Man
>
> Looking into the ChaosMonkey code a bit, and it seems like this class -- particularly
the way {{monkeyThread}} is defined -- uses randomness in a way that makes it extremely unlikely
that it will ever create reproducible failures.
> Obviously in any test where there are multiple concurrent threads, timing issues might
prevent test reproducibility -- but in this case, even the sequence of "chaos" actions the
monkeyThread takes won't be reproducible if anyother concurrent test thread accesses {{LuceneTestCase.random()}}
...
> {code}
>       public void run() {
>         while (!stop) {
>           try {
>     
>             Random random = LuceneTestCase.random();
>             // ... lots of stuff using random, or calling methods that use LuceneTestCase.random()
directly
> {code}
> It seems like it would be a lot better if ChaosMonkey's constructor created it's own
private {{Random chaosRand}} using {{LuceneTestCase.random()}} as a seed, and then used {{chaosRand}}
to make all random choices in it's methods.
> That way at least the sequence of chaotic operations made by ChaosMonkey would be consistent
for a given test seed, even if the exact timing/interleaving of those operations relative
to other operations by other threads couldn't be garunteed.



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