[GitHub] [hadoop-ozone] elek opened a new pull request #6: HDDS-2214. TestSCMContainerPlacementRackAware has an intermittent fai…

[GitBox <gi...@apache.org>]

elek opened a new pull request #6: HDDS-2214. TestSCMContainerPlacementRackAware has an intermittent fai…
URL: https://github.com/apache/hadoop-ozone/pull/6
 
 
    ## What changes were proposed in this pull request?
   
   Fixing an intermittent unit test.
   
    ## What is the problem
   
   For example from the nightly build:
   
   ```
     <testcase name="testNoFallback[8]" classname="org.apache.hadoop.hdds.scm.container.placement.algorithms.TestSCMContainerPlacementRackAware" time="0.014">
               <failure type="java.lang.AssertionError">java.lang.AssertionError
           	at org.junit.Assert.fail(Assert.java:86)
           	at org.junit.Assert.assertTrue(Assert.java:41)
           	at org.junit.Assert.assertTrue(Assert.java:52)
           	at org.apache.hadoop.hdds.scm.container.placement.algorithms.TestSCMContainerPlacementRackAware.testNoFallback(TestSCMContainerPlacementRackAware.java:276)
           	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
           	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
           	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
           	at java.lang.reflect.Method.invoke(Method.java:498)
           	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
   ```
   
   The problem is in the testNoFallback:
   
   Let's say we have 11 nodes (from parameter) and we would like to choose 5 nodes (hard coded in the test).
   
   As the first two replicas are chosen from the same rack an all the other from different racks it's not possible, so we except a failure.
   
   But we have an assertion that the success count is at least 3. But this is true only if the first two replicas are placed to the rack1 (5 nodes) or rack2 (5nodes). If the replica is placed to the rack3 (one node) it will fail immediately:
   
   Lucky case when we have success count > 3
   
   ```
    rack1 -- node1 
    rack1 -- node2 -- FIRST replica
    rack1 -- node3 -- SECOND replica
    rack1 -- node4
    rack1 -- node5 
    rack2 -- node6
    rack2 -- node7 -- THIRD replica
    rack2 -- node8
    rack2 -- node9 
    rack2 -- node10
    rack3 -- node11 -- FOURTH replica{code}
   ```
   
    The specific case when we have success count == 1, as we can't choose the second replica on rack3 (This is when the test is failing)
   
   ```
    rack1 -- node1 
    rack1 -- node2
    rack1 -- node3
    rack1 -- node4
    rack1 -- node5 
    rack2 -- node6
    rack2 -- node7
    rack2 -- node8
    rack2 -- node9 
    rack2 -- node10
    rack3 -- node11 -- FIRST replica{code}
    ```
   
    ## What is the link to the Apache JIRA
   
   https://issues.apache.org/jira/browse/HDDS-2289
   
    ## How was this patch tested?
   
   With Intellij you can execute the unit test multiple times (1000x) or until the next failure. Execute it with or without the patch. Usually I got the problem during the first 100 execution. 

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