[GitHub] [incubator-zipkin-brave] devinsba commented on a change in pull request #908: Fixes some edge cases around sampler resetting

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

devinsba commented on a change in pull request #908: Fixes some edge cases around sampler resetting
URL: https://github.com/apache/incubator-zipkin-brave/pull/908#discussion_r283461739
 
 

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 File path: brave/src/main/java/brave/sampler/RateLimitingSampler.java
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 @@ -55,14 +55,17 @@ public static Sampler create(int tracesPerSecond) {
     long updateAt = nextReset.get();
 
     long nanosUntilReset = -(now - updateAt); // because nanoTime can be negative
-    boolean shouldReset = nanosUntilReset <= 0;
-    if (shouldReset) {
-      if (nextReset.compareAndSet(updateAt, updateAt + NANOS_PER_SECOND)) {
-        usage.set(0);
-      }
+    if (nanosUntilReset <= 0) {
+      // Attempt to move into the next sampling interval.
+      // nanosUntilReset is now invalid regardless of race winner, so we can't sample based on it.
+      if (nextReset.compareAndSet(updateAt, updateAt + NANOS_PER_SECOND)) usage.set(0);
 
 Review comment:
   The recursion below should also solve that, but having not seen that problem (`updateAt` being more than a second in the past) in my first reading, the recursion is now screaming stack overflow to me so I think that needs to be addressed

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