> @@ -126,6 +127,9 @@ public void imposeBackoffExponentialDelay(long period,
> int pow, int failureCount
> public void imposeBackoffExponentialDelay(long period, long maxPeriod,
> int pow, int failureCount, int max,
> String commandDescription) {
> long delayMs = (long) (period * Math.pow(failureCount, pow));
> + // Add random delay to avoid thundering herd problem when multiple
> + // simultaneous failed requests retry after sleeping for the same
> delay.
> + delayMs += new Random().nextInt((int) (delayMs / 10));
```delayMs``` defaults to a small value, 50 ms, although scales up to 500 ms.
10% jitter may be suboptimal; I chose this value to agree with our existing
tests.
Java 6 Javadoc does not guarantee thread-safety:
http://docs.oracle.com/javase/6/docs/api/java/util/Random.html
Although StackOverflow and the Java bug tracker suggest that it is:
http://stackoverflow.com/questions/5819638/is-random-class-thread-safe
http://bugs.java.com/bugdatabase/view_bug.do?bug_id=6362070
Prefer to keep this simple if possible since we only see this on the uncommon
failure path.
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