statistics_storage.hpp

#pragma once
 
#include <string_view>
#include <unordered_map>
 
#include <userver/engine/shared_mutex.hpp>
#include <userver/utils/statistics/entry.hpp>
 
#include <userver/ugrpc/impl/statistics.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace ugrpc::impl {
 
/// Clients are created on-the-fly, so we must use a separate stable container
/// for storing their statistics.
class StatisticsStorage final {
 public:
  explicit StatisticsStorage(utils::statistics::Storage& statistics_storage,
                             std::string_view domain);
 
  StatisticsStorage(const StatisticsStorage&) = delete;
  StatisticsStorage& operator=(const StatisticsStorage&) = delete;
 
  ~StatisticsStorage();
 
  ugrpc::impl::ServiceStatistics& GetServiceStatistics(
      const ugrpc::impl::StaticServiceMetadata& metadata);
 
  // Can only be called on StatisticsStorage for gRPC services (not clients).
  // Can only be called strictly after all the components are loaded.
  // gRPC services must not be [un]registered during GetStartedRequests().
  std::uint64_t GetStartedRequests() const;
 
 private:
  // Pointer to service name from its metadata is used as a unique service ID
  using ServiceId = const char*;
 
  void ExtendStatistics(utils::statistics::Writer& writer);
 
  // std::equal_to<const char*> specialized in arcadia/util/str_stl.h
  // so we need to define our own comparer to use it in map and avoid
  // specialization after instantiation problem
  struct ServiceIdComparer final {
    bool operator()(ServiceId lhs, ServiceId rhs) const { return lhs == rhs; }
  };
 
  std::unordered_map<ServiceId, ugrpc::impl::ServiceStatistics,
                     std::hash<ServiceId>, ServiceIdComparer>
      service_statistics_;
  engine::SharedMutex mutex_;
 
  utils::statistics::Entry statistics_holder_;
};
 
}  // namespace ugrpc::impl
 
USERVER_NAMESPACE_END