cache_statistics.hpp

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#pragma once
 
/// @file userver/cache/cache_statistics.hpp
/// @brief Statistics collection for components::CachingComponentBase
 
#include <atomic>
#include <chrono>
#include <cstddef>
 
#include <userver/cache/update_type.hpp>
#include <userver/utils/impl/internal_tag.hpp>
#include <userver/utils/statistics/fwd.hpp>
#include <userver/utils/statistics/rate_counter.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace cache {
 
namespace impl {
 
struct UpdateStatistics final {
    utils::statistics::RateCounter update_attempt_count{0};
    utils::statistics::RateCounter update_no_changes_count{0};
    utils::statistics::RateCounter update_failures_count{0};
 
    utils::statistics::RateCounter documents_read_count{0};
    utils::statistics::RateCounter documents_parse_failures{0};
 
    std::atomic<std::chrono::steady_clock::time_point> last_update_start_time{{}};
    std::atomic<std::chrono::steady_clock::time_point> last_successful_update_start_time{{}};
    std::atomic<std::chrono::milliseconds> last_update_duration{{}};
};
 
void DumpMetric(utils::statistics::Writer& writer, const UpdateStatistics& stats);
 
struct Statistics final {
    UpdateStatistics full_update;
    UpdateStatistics incremental_update;
    std::atomic<std::size_t> documents_current_count{0};
    std::atomic<bool> is_first_sync_update_complete{false};  // Success or failure does not matter here.
};
 
void DumpMetric(utils::statistics::Writer& writer, const Statistics& stats);
 
enum class UpdateState { kNotFinished, kSuccess, kNoChanges, kFailure };
 
}  // namespace impl
 
/// @brief Allows a specific cache to fill cache statistics during an `Update`.
///
/// If `Update` returns without throwing an exception and without calling one
/// of the `Finish*` methods, the behavior is undefined.
///
/// See components::CachingComponentBase::Set() for information on actual cache
/// update, rather than statistics update.
class UpdateStatisticsScope final {
public:
    /// @cond
    // Note: DO NOT try to create `UpdateStatisticsScope` manually for manual `Update` calls.
    // CachingComponentBase's internals WILL be corrupted.
    // Call `InvalidateAsync` or `UpdateSyncDebug` instead.
    // For internal use only.
    UpdateStatisticsScope(utils::impl::InternalTag, impl::Statistics& stats, cache::UpdateType type);
 
    ~UpdateStatisticsScope();
 
    // For internal use only.
    impl::UpdateState GetState(utils::impl::InternalTag) const;
    /// @endcond
 
    /// @brief Mark that the `Update` has finished with changes
    /// @param total_documents_count the new total number of items stored in the cache
    void Finish(std::size_t total_documents_count);
 
    /// @brief Mark that the `Update` has finished without changes
    void FinishNoChanges();
 
    /// @brief Mark that the `Update` failed
    void FinishWithError();
 
    /// @brief Each item received from the data source should be accounted with
    /// this function
    /// @note This method can be called multiple times per `Update`
    /// @param add the number of items (both valid and non-valid) newly received
    void IncreaseDocumentsReadCount(std::size_t add);
 
    /// @brief Each received item that failed validation should be accounted with
    /// this function, in addition to IncreaseDocumentsReadCount
    /// @note This method can be called multiple times per `Update`
    /// @param add the number of non-valid items newly received
    void IncreaseDocumentsParseFailures(std::size_t add);
 
private:
    void DoFinish(impl::UpdateState new_state);
 
    impl::Statistics& stats_;
    impl::UpdateStatistics& update_stats_;
    impl::UpdateState state_{impl::UpdateState::kNotFinished};
    const std::chrono::steady_clock::time_point update_start_time_;
};
 
}  // namespace cache
 
USERVER_NAMESPACE_END