[jira] [Created] (HADOOP-17222) Create socket address combined with cache to speed up hdfs client choose DataNode

["fanrui (Jira)" <ji...@apache.org>]

fanrui created HADOOP-17222:
-------------------------------

             Summary: Create socket address combined with cache to speed up hdfs client choose DataNode
                 Key: HADOOP-17222
                 URL: https://issues.apache.org/jira/browse/HADOOP-17222
             Project: Hadoop Common
          Issue Type: Improvement
          Components: common, hdfs-client
         Environment: HBase version: 2.1.0
JVM: -Xmx2g -Xms2g 
hadoop hdfs version: 2.7.4
disk:SSD
OS:CentOS Linux release 7.4.1708 (Core)
JMH Benchmark: @Fork(value = 1) 
@Warmup(iterations = 300) 
@Measurement(iterations = 300)
            Reporter: fanrui
         Attachments: After Optimization remark.png, Before Optimization remark.png

Hdfs client selects best DN for hdfs Block. method call stack:

DFSInputStream.chooseDataNode -> getBestNodeDNAddrPair -> NetUtils.createSocketAddr

NetUtils.createSocketAddr creates the corresponding InetSocketAddress based on the host and port. There are some heavier operations in the NetUtils.createSocketAddr method, for example: URI.create(target), so NetUtils.createSocketAddr takes more time to execute.

The following is my performance report. The report is based on HBase calling hdfs. HBase is a high-frequency access client for hdfs, because HBase read operations often access a small DataBlock (about 64k) instead of the entire HFile. In the case of high frequency access, the NetUtils.createSocketAddr method is time-consuming.
h3. Test Environment：

 
{code:java}
HBase version: 2.1.0
JVM: -Xmx2g -Xms2g 
hadoop hdfs version: 2.7.4
disk:SSD
OS:CentOS Linux release 7.4.1708 (Core)
JMH Benchmark: @Fork(value = 1) 
@Warmup(iterations = 300) 
@Measurement(iterations = 300)
{code}
h4. Before Optimization FlameGraph:

In the figure, we can see that DFSInputStream.getBestNodeDNAddrPair accounts for 4.86% of the entire CPU, and the creation of URIs accounts for a larger proportion.

{{!Before Optimization remark.png|thumbnail!}}
h3. Optimization ideas:

NetUtils.createSocketAddr creates InetSocketAddress based on host and port. Here we can add Cache to InetSocketAddress. The key of Cache is host and port, and the value is InetSocketAddress.
h4. After Optimization FlameGraph:

In the figure, we can see that DFSInputStream.getBestNodeDNAddrPair accounts for 0.54% of the entire CPU. Here, ConcurrentHashMap is used as the Cache, and the ConcurrentHashMap.get() method gets data from the Cache. The CPU usage of DFSInputStream.getBestNodeDNAddrPair has been optimized from 4.86% to 0.54%.

{{!After Optimization remark.png|thumbnail!}} 
h3. Original FlameGraph link:

[Before Optimization|https://drive.google.com/file/d/133L5m75u2tu_KgKfGHZLEUzGR0XAfUl6/view?usp=sharing]

[After Optimization FlameGraph|https://drive.google.com/file/d/133L5m75u2tu_KgKfGHZLEUzGR0XAfUl6/view?usp=sharing]



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