void cleanupExpiredSuppressions() {
    Suppression<C> expiredSuppression;
    while ((expiredSuppression = suppressions.poll()) != null) {
      cache.remove(expiredSuppression.context, expiredSuppression);
    }
  }
Returns true if a given context should be invoked.
zipkin/src/main/java/zipkin2/internal/DelayLimiter.java