[jira] [Created] (HDFS-9436) Make NNThroughputBenchmark$BlockReportStats run with 10 datanodes by default

["Mingliang Liu (JIRA)" <ji...@apache.org>]

Mingliang Liu created HDFS-9436:
-----------------------------------

             Summary: Make NNThroughputBenchmark$BlockReportStats run with 10 datanodes by default
                 Key: HDFS-9436
                 URL: https://issues.apache.org/jira/browse/HDFS-9436
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: test
            Reporter: Mingliang Liu
            Assignee: Mingliang Liu
             Fix For: 2.8.0


Currently, the {{NNThroughputBenchmark}} test {{BlockReportStats}} relies on sorted {{datanodes}} array in the lexicographical order of datanode's {{xferAddr}}.
* There is an assertion of datanode's {{xferAddr}} lexicographical order when filling the {{datanodes}}, see [the code|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java#L1152].
* When searching the datanode by {{DatanodeInfo}}, it uses binary search against the {{datanodes}} array, see [the code|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java#L1187]

In {{DatanodeID}}, the {{xferAddr}} is defined as {{host:port}}. In {{NNThroughputBenchmark}}, the port is simply _the index of the tiny datanode_ plus one.

The problem here is that, when there are more than 9 tiny datanodes ({{numThreads}}), the lexicographical order of datanode's {{xferAddr}} will be invalid as the string value of datanode index is not in lexicographical order any more. For example, 
{code}
...
192.168.54.40:8
192.168.54.40:9
192.168.54.40:10
192.168.54.40:11
...
{code}

{{192.168.54.40:9}} is greater than {{192.168.54.40:10}}. The assertion will fail and the binary search won't work.

The simple fix is to calculate the datanode index by port directly, instead of using binary search.



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