private ChannelRef pickLeastBusyChannel()

in grpc-gcp/src/main/java/com/google/cloud/grpc/GcpManagedChannel.java [1198:1268]
63 lines of code
21 McCabe index (conditional complexity)

  private ChannelRef pickLeastBusyChannel(boolean forFallback) {
    ChannelRef first = createFirstChannel();
    if (first != null) {
      return first;
    }

    // Pick the least busy channel and the least busy ready and not overloaded channel (this could
    // be the same channel or different or no channel).
    ChannelRef channelCandidate = channelRefs.get(0);
    int minStreams = channelCandidate.getActiveStreamsCount();
    ChannelRef readyCandidate = null;
    int readyMinStreams = Integer.MAX_VALUE;

    for (ChannelRef channelRef : channelRefs) {
      int cnt = channelRef.getActiveStreamsCount();
      if (cnt < minStreams) {
        minStreams = cnt;
        channelCandidate = channelRef;
      }
      if (cnt < readyMinStreams
          && !fallbackMap.containsKey(channelRef.getId())
          && channelRef.getActiveStreamsCount() < DEFAULT_MAX_STREAM) {
        readyMinStreams = cnt;
        readyCandidate = channelRef;
      }
    }

    if (!fallbackEnabled) {
      if (channelRefs.size() < maxSize && minStreams >= maxConcurrentStreamsLowWatermark) {
        ChannelRef newChannel = tryCreateNewChannel();
        if (newChannel != null) {
          return newChannel;
        }
      }
      return channelCandidate;
    }

    if (channelRefs.size() < maxSize && readyMinStreams >= maxConcurrentStreamsLowWatermark) {
      ChannelRef newChannel = tryCreateNewChannel();
      if (newChannel != null) {
        if (!forFallback && readyCandidate == null) {
          if (logger.isLoggable(Level.FINEST)) {
            logger.finest(log("Fallback to newly created channel %d", newChannel.getId()));
          }
          fallbacksSucceeded.incrementAndGet();
        }
        return newChannel;
      }
    }

    if (readyCandidate != null) {
      if (!forFallback && readyCandidate.getId() != channelCandidate.getId()) {
        if (logger.isLoggable(Level.FINEST)) {
          logger.finest(
              log(
                  "Picking fallback channel: %d -> %d",
                  channelCandidate.getId(), readyCandidate.getId()));
        }
        fallbacksSucceeded.incrementAndGet();
      }
      return readyCandidate;
    }

    if (!forFallback) {
      if (logger.isLoggable(Level.FINEST)) {
        logger.finest(log("Failed to find fallback for channel %d", channelCandidate.getId()));
      }
      fallbacksFailed.incrementAndGet();
    }
    return channelCandidate;
  }