code: public boolean report(ReportRequest req) {
      if (cache == null) {
        return false;
      }
      Preconditions.checkArgument(req.getServiceName().equals(serviceName), "service name mismatch");
      if (hasHighImportanceOperation(req)) {
        return false;
      }
      Map<String, Operation> bySignature = opsBySignature(req);
  
      // Concurrency: all threads wait while the current thread updates the cache.
      //
      // It's better for overall latency to have one thread complete cache update at a time than have
      // multiple threads interleave updates with the increased cpu cost due to increased context
      // switching.
      //
      // No i/o or computation is occurring, so the wait time should be relatively small and
      // depend on the number of waiting threads.
      synchronized (cache) {
        for (Map.Entry<String, Operation> entry : bySignature.entrySet()) {
          String signature = entry.getKey();
          OperationAggregator agg = cache.getIfPresent(signature);
          if (agg == null) {
            cache.put(signature, new OperationAggregator(entry.getValue(), kinds));
          } else {
            agg.add(entry.getValue());
          }
        }
      }
      return true;
    }
docs: Adds a report request to this instance's cache.
  
  @param req a {@code ReportRequest} to cache in this instance.
  @return {@code true} if {@code req} was cached successfully, otherwise {@code false}