Class CensusStatsModule

census/src/main/java/io/grpc/census/CensusStatsModule.java:79–822

Provides factories for StreamTracer that records stats to Census. On the client-side, a factory is created for each call, and the factory creates a stream tracer for each attempt. If there is no stream created when the call is ended, we still create a tracer. It's the tracer that reports

 * it's the tracer that reports the summary to Census.
 */
final class CensusStatsModule {
  private static final Logger logger = Logger.getLogger(CensusStatsModule.class.getName());
  private static final double NANOS_PER_MILLI = TimeUnit.MILLISECONDS.toNanos(1);

  private final Tagger tagger;
  private final StatsRecorder statsRecorder;
  private final Supplier<Stopwatch> stopwatchSupplier;
  @VisibleForTesting
  final Metadata.Key<TagContext> statsHeader;
  private final boolean propagateTags;
  private final boolean recordStartedRpcs;
  private final boolean recordFinishedRpcs;
  private final boolean recordRealTimeMetrics;
  private final boolean recordRetryMetrics;

  /**
   * Creates a {@link CensusStatsModule} with the default OpenCensus implementation.
   */
  CensusStatsModule(Supplier<Stopwatch> stopwatchSupplier,
      boolean propagateTags, boolean recordStartedRpcs, boolean recordFinishedRpcs,
      boolean recordRealTimeMetrics, boolean recordRetryMetrics) {
    this(
        Tags.getTagger(),
        Tags.getTagPropagationComponent().getBinarySerializer(),
        Stats.getStatsRecorder(),
        stopwatchSupplier,
        propagateTags, recordStartedRpcs, recordFinishedRpcs, recordRealTimeMetrics,
        recordRetryMetrics);
  }

  /**
   * Creates a {@link CensusStatsModule} with the given OpenCensus implementation.
   */
  CensusStatsModule(
      final Tagger tagger,
      final TagContextBinarySerializer tagCtxSerializer,
      StatsRecorder statsRecorder, Supplier<Stopwatch> stopwatchSupplier,
      boolean propagateTags, boolean recordStartedRpcs, boolean recordFinishedRpcs,
      boolean recordRealTimeMetrics, boolean recordRetryMetrics) {
    this.tagger = checkNotNull(tagger, "tagger");
    this.statsRecorder = checkNotNull(statsRecorder, "statsRecorder");
    checkNotNull(tagCtxSerializer, "tagCtxSerializer");
    this.stopwatchSupplier = checkNotNull(stopwatchSupplier, "stopwatchSupplier");
    this.propagateTags = propagateTags;
    this.recordStartedRpcs = recordStartedRpcs;
    this.recordFinishedRpcs = recordFinishedRpcs;
    this.recordRealTimeMetrics = recordRealTimeMetrics;
    this.recordRetryMetrics = recordRetryMetrics;
    this.statsHeader =
        Metadata.Key.of("grpc-tags-bin", new Metadata.BinaryMarshaller<TagContext>() {
            @Override
            public byte[] toBytes(TagContext context) {
              // TODO(carl-mastrangelo): currently we only make sure the correctness. We may need to
              // optimize out the allocation and copy in the future.
              try {
                return tagCtxSerializer.toByteArray(context);
              } catch (TagContextSerializationException e) {
                throw new RuntimeException(e);