Class MutationBatcher

getting-started/gke/index_gcs.cc:41–65

using google::cloud::cpp_samples::UpdateObjectMetadata;

class MutationBatcher {
 public:
  MutationBatcher(spanner::Client client);

  future<Status> Push(gcs::ObjectMetadata const& o);
  // Return the number of mutations processed since the last Flush().
  std::int64_t Flush();

  void ReapBackgroundTasks();

 private:
  void FlushIfNeeded(std::unique_lock<std::mutex> const&);
  void Flush(std::unique_lock<std::mutex> const&);

  struct Item {
    spanner::Mutation mutation;
    promise<Status> done;
  };

  spanner::Client client_;
  std::mutex mu_;
  std::vector<Item> items_;
  std::vector<std::future<void>> background_tasks_;
  std::int64_t mutation_count_ = 0;
};

void IndexGcsPrefix(pubsub::Message m, pubsub::AckHandler h, gcs::Client client,
                    pubsub::Publisher publisher,