Question

我注意到Hystrix有两种线程隔离策略：Thread和Semaphore。

默认情况下，Hystrix使用线程策略并通过hystrix.threadpool.default.coreSize控制它，因为具有相同组密钥的caundmand将使用相同的线程池。所以它基于组密钥。

当Hystrix使用信号量策略时，信号量将保存在ConcurrentHashMap中，键是命令名，是否基于命令名？

以下是代码：

/**
 * Get the TryableSemaphore this HystrixCommand should use for execution if not running in a separate thread.
 *
 * @return TryableSemaphore
 */
protected TryableSemaphore getExecutionSemaphore() {
  if (properties.executionIsolationStrategy().get() == ExecutionIsolationStrategy.SEMAPHORE) {
    if (executionSemaphoreOverride == null) {
      TryableSemaphore _s = executionSemaphorePerCircuit.get(commandKey.name());
      if (_s == null) {
        // we didn't find one cache so setup
        executionSemaphorePerCircuit.putIfAbsent(commandKey.name(), new TryableSemaphoreActual(properties.executionIsolationSemaphoreMaxConcurrentRequests()));
        // assign whatever got set (this or another thread)
        return executionSemaphorePerCircuit.get(commandKey.name());
      } else {
        return _s;
      }
    } else {
      return executionSemaphoreOverride;
    }
  } else {
    // return NoOp implementation since we're not using SEMAPHORE isolation
    return TryableSemaphoreNoOp.DEFAULT;
  }
}

为什么他们的范围不同？我写了一些测试代码来证明它：

public static void main(String[] args) throws InterruptedException {
  int i = 0;
  while (i++ < 20) {
    final int index = i;
    new Thread(() -> {
      System.out.println(new ThreadIsolationCommand(index).execute());
      System.out.println(new SemaphoreIsolationCommand(index).execute());
    }).start();
  }
}

static class ThreadIsolationCommand extends HystrixCommand<String> {

  private int index;

  protected ThreadIsolationCommand(int index) {
    super(
        Setter
            .withGroupKey(HystrixCommandGroupKey.Factory.asKey("ThreadIsolationCommandGroup"))
            .andCommandKey(HystrixCommandKey.Factory.asKey(String.valueOf(index)))
            .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                .withExecutionIsolationStrategy(HystrixCommandProperties.ExecutionIsolationStrategy.THREAD)
            )
            .andThreadPoolPropertiesDefaults(HystrixThreadPoolProperties.Setter()
                .withCoreSize(10)
            )
    );
    this.index = index;
  }

  @Override
  protected String run() throws Exception {
    Thread.sleep(500);
    return "Hello Thread " + index;
  }

  @Override
  protected String getFallback() {
    return "Fallback Thread " + index;
  }
}

static class SemaphoreIsolationCommand extends HystrixCommand<String> {

  private int index;

  protected SemaphoreIsolationCommand(int index) {
    super(
        Setter
            .withGroupKey(HystrixCommandGroupKey.Factory.asKey("SemaphoreIsolationCommandGroup"))
            .andCommandKey(HystrixCommandKey.Factory.asKey(String.valueOf(index)))
            .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                .withExecutionIsolationStrategy(HystrixCommandProperties.ExecutionIsolationStrategy.SEMAPHORE)
                .withExecutionIsolationSemaphoreMaxConcurrentRequests(10)
            )
    );
    this.index = index;
  }

  @Override
  protected String run() throws Exception {
    Thread.sleep(500);
    return "Hello Semaphore " + index;
  }

  @Override
  protected String getFallback() {
    return "Fallback Semaphore " + index;
  }
}

此命令具有相同的组密钥和不同的名称，结果为：

Fallback Thread 9
Fallback Thread 1
Fallback Thread 8
Fallback Thread 19
Fallback Thread 20
Fallback Thread 14
Fallback Thread 3
Fallback Thread 13
Fallback Thread 17
Fallback Thread 10
Hello Thread 5
Hello Semaphore 17
Hello Semaphore 14
Hello Thread 2
Hello Semaphore 3
Hello Thread 7
Hello Thread 15
Hello Thread 4
Hello Semaphore 13
Hello Semaphore 1
Hello Thread 11
Hello Semaphore 20
Hello Semaphore 19
Hello Thread 18
Hello Thread 12
Hello Semaphore 8
Hello Semaphore 9
Hello Thread 6
Hello Thread 16
Hello Semaphore 10
Hello Semaphore 5
Hello Semaphore 2
Hello Semaphore 7
Hello Semaphore 15
Hello Semaphore 4
Hello Semaphore 11
Hello Semaphore 12
Hello Semaphore 6
Hello Semaphore 18
Hello Semaphore 16

只有线程策略失败。是吗？

基于组密钥或命令名的Hystrix线程隔离？

0 个答案: