adriancole 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_r289582385
##########
File path: brave/src/main/java/brave/sampler/RateLimitingSampler.java
##########
@@ -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:
I think maybe the below is the easier way to get to the point (we should be
working off "now"), I will also add a unit test so recursion worries float away.
```diff
--- a/brave/src/main/java/brave/sampler/RateLimitingSampler.java
+++ b/brave/src/main/java/brave/sampler/RateLimitingSampler.java
@@ -74,7 +74,7 @@ public class RateLimitingSampler extends Sampler {
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);
+ if (nextReset.compareAndSet(updateAt, now + NANOS_PER_SECOND))
usage.set(0);
// recurse as it is simpler than resetting all the locals.
// reset happens once per second, this code doesn't take a second, so
no infinite recursion.
```
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