Merge pull request Netflix#1247 from yanglifan/smart-config-pool-size

Set the thread pool size only when the configuration is changed.

hystrix-core/src/main/java/com/netflix/hystrix/HystrixThreadPool.java

@@ -204,8 +204,13 @@ public Scheduler getScheduler(Func0<Boolean> shouldInterruptThread) {
  // allow us to change things via fast-properties by setting it each time
  private void touchConfig() {
  final int dynamicCoreSize = properties.coreSize().get();
- threadPool.setCorePoolSize(dynamicCoreSize);
- threadPool.setMaximumPoolSize(dynamicCoreSize); // we always want maxSize the same as coreSize, we are not using a dynamically resizing pool
+
+ // In JDK 6, setCorePoolSize and setMaximumPoolSize will execute a lock operation. Avoid them if the pool size is not changed.
+ if (threadPool.getCorePoolSize() != dynamicCoreSize) {
+ threadPool.setCorePoolSize(dynamicCoreSize);
+ threadPool.setMaximumPoolSize(dynamicCoreSize); // we always want maxSize the same as coreSize, we are not using a dynamically resizing pool
+ }
+
  threadPool.setKeepAliveTime(properties.keepAliveTimeMinutes().get(), TimeUnit.MINUTES); // this doesn't really matter since we're not resizing
  }