code: protected void addBasicMetrics(Collection<Metric<?>> result) {
          // NOTE: ManagementFactory must not be used here since it fails on GAE
          Runtime runtime = Runtime.getRuntime();
          result.add(newMemoryMetric("mem", runtime.totalMemory() + getTotalNonHeapMemoryIfPossible()));
          result.add(newMemoryMetric("mem.free", runtime.freeMemory()));
          result.add(new Metric<>("processors", runtime.availableProcessors()));
          result.add(new Metric<>("instance.uptime", System.currentTimeMillis() - this.timestamp));
      }
docs: Add basic system metrics.
  
  @param result the result