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Race condition when creating HystrixThreadPool #340

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Dec 11, 2014
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Race condition when creating HystrixThreadPool #340

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19 changes: 5 additions & 14 deletions hystrix-core/src/main/java/com/netflix/hystrix/HystrixThreadPool.java
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Original file line number Diff line number Diff line change
Expand Up @@ -100,21 +100,12 @@ public interface HystrixThreadPool {
}

// if we get here this is the first time so we need to initialize

// Create and add to the map ... use putIfAbsent to atomically handle the possible race-condition of
// 2 threads hitting this point at the same time and let ConcurrentHashMap provide us our thread-safety
// If 2 threads hit here only one will get added and the other will get a non-null response instead.
HystrixThreadPool poolForKey = threadPools.putIfAbsent(key, new HystrixThreadPoolDefault(threadPoolKey, propertiesBuilder));
if (poolForKey == null) {
// this means the putIfAbsent step just created a new one so let's retrieve and return it
HystrixThreadPool threadPoolJustCreated = threadPools.get(key);
// return it
return threadPoolJustCreated;
} else {
// this means a race occurred and while attempting to 'put' another one got there before
// and we instead retrieved it and will now return it
return poolForKey;
synchronized (HystrixThreadPool.class) {
if (!threadPools.containsKey(key)) {
threadPools.put(key, new HystrixThreadPoolDefault(threadPoolKey, propertiesBuilder));
}
}
return threadPools.get(key);
}

/**
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