[GitHub] lexburner opened a new issue #2444: [Enhancement] Replace Random with ThreadLocalRandom

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

lexburner opened a new issue #2444: [Enhancement] Replace Random with ThreadLocalRandom
URL: https://github.com/apache/incubator-dubbo/issues/2444
 
 
   ### Details
   
   A little change, replace `Random` with `ThreadLocalRandom` .
   
   Use of ThreadLocalRandom rather than shared Random objects in concurrent programs will typically encounter much less overhead and contention.
   
   Use of ThreadLocalRandom is particularly appropriate when multiple tasks .
   
   ### Benchmark
   
   There are some attentions need to be noticed before benchmark.
   
   1. third-party dependency need use carefully.
   2. bugs fix need to trace from upstream repository.
   3. performance benchmark
   
   I have compared the three cases : `Random`,`ThreadLocalRandom` from JDK, `ThreadLocalRandom` from netty.
   
   ```
   @BenchmarkMode({Mode.AverageTime})
   @OutputTimeUnit(TimeUnit.NANOSECONDS)
   @Warmup(iterations = 3, time = 5)
   @Measurement(iterations = 3, time = 5)
   @Threads(50)
   @Fork(1)
   @State(Scope.Benchmark)
   public class RandomBenchmark {
   
       Random random = new Random();
   
       @Benchmark
       public int random() {
           return random.nextInt();
       }
   
       @Benchmark
       public int threadLocalRandom() {
           return ThreadLocalRandom.current().nextInt();
       }
   
       @Benchmark
       public int nettyThreadLocalRandom() {
           return io.netty.util.internal.ThreadLocalRandom.current().nextInt();
       }
   
       public static void main(String[] args) throws RunnerException {
           Options opt = new OptionsBuilder()
                   .include(RandomBenchmark.class.getSimpleName())
                   .build();
   
           new Runner(opt).run();
       }
   
   }
   ```
   and below is our benchmark result under 50 concurrency
   ```
   Benchmark                               Mode  Cnt     Score      Error  Units
   RandomBenchmark.nettyThreadLocalRandom  avgt    3   160.321 ±   83.518  ns/op
   RandomBenchmark.random                  avgt    3  3281.972 ± 2093.187  ns/op
   RandomBenchmark.threadLocalRandom       avgt    3    91.505 ±   39.702  ns/op
   ```
   
   From the result we can know the truth
   > Both the performance (according to above benchmark) and the stability（it is from the JDK）
   > JDK 's ThreadLocalRandom looks good. 

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