feat userver: use RegisterScope() API for metrics & cache

commit_hash:aac3515679e852a16316374728b845c64a522aa5

Author: segoon

core/functional_tests/cache_update/service.cpp

@@ -23,13 +23,7 @@ class AlertCache final : public components::CachingComponentBase<Data> {
 public:
     static constexpr std::string_view kName = "alert-cache";
 
-    AlertCache(const components::ComponentConfig& config, const components::ComponentContext& context)
-        : CachingComponentBase(config, context)
-    {
-        CacheUpdateTrait::StartPeriodicUpdates();
-    }
-
-    ~AlertCache() override { CacheUpdateTrait::StopPeriodicUpdates(); }
+    using components::CachingComponentBase<Data>::CachingComponentBase;
 
     void Update(
         cache::UpdateType type,
@@ -53,11 +47,7 @@ class CacheSample final : public components::CachingComponentBase<Data> {
 
     CacheSample(const components::ComponentConfig& config, const components::ComponentContext& context)
         : CachingComponentBase(config, context)
-    {
-        CacheUpdateTrait::StartPeriodicUpdates();
-    }
-
-    ~CacheSample() override { CacheUpdateTrait::StopPeriodicUpdates(); }
+    {}
 
     void Update(
         cache::UpdateType /*type*/,

core/functional_tests/dump_coroutines/service.cpp

@@ -24,11 +24,7 @@ class CachedTranslations final : public components::CachingComponentBase<KeyTran
 
     CachedTranslations(const components::ComponentConfig& config, const components::ComponentContext& context)
         : CachingComponentBase(config, context)
-    {
-        CacheUpdateTrait::StartPeriodicUpdates();
-    }
-
-    ~CachedTranslations() override { CacheUpdateTrait::StopPeriodicUpdates(); }
+    {}
 
     void Update(
         cache::UpdateType /*type*/,

core/functional_tests/metrics/service.cpp

@@ -23,11 +23,7 @@ class CachedTranslations final : public components::CachingComponentBase<KeyTran
 
     CachedTranslations(const components::ComponentConfig& config, const components::ComponentContext& context)
         : CachingComponentBase(config, context)
-    {
-        CacheUpdateTrait::StartPeriodicUpdates();
-    }
-
-    ~CachedTranslations() override { CacheUpdateTrait::StopPeriodicUpdates(); }
+    {}
 
     void Update(
         cache::UpdateType /*type*/,

core/include/userver/cache/cache_update_trait.hpp

@@ -66,17 +66,6 @@ class CacheUpdateTrait {
         kNoFirstUpdate = 1 << 0,
     };
 
-    /// Starts periodic updates
-    void StartPeriodicUpdates(utils::Flags<Flag> flags = {});
-
-    /// @brief Stops periodic updates
-    /// @warning Should be called in destructor of derived class.
-    void StopPeriodicUpdates();
-
-    void AssertPeriodicUpdateStarted();
-
-    void AssertPeriodicUpdateStopped();
-
     /// Called in `CachingComponentBase::Set` during update to indicate
     /// that the cached data has been modified
     void OnCacheModified();
@@ -145,7 +134,23 @@ class CacheUpdateTrait {
         UpdateStatisticsScope& stats_scope
     ) = 0;
 
+    /// @brief Returns flags for cache start.
+    virtual utils::Flags<Flag> GetStartFlags() const;
+
+    /// @brief Call this to start periodic updates just now,
+    /// not after the constuctor.
+    void EarlyStartPeriodicUpdates(utils::Flags<Flag> flags);
+
+    /// @cond
+    // For internal use only
+    void EarlyStopPeriodicUpdates();
+    /// @endcond
+
 private:
+    void StartPeriodicUpdates();
+
+    void StopPeriodicUpdates();
+
     virtual void Cleanup() = 0;
 
     virtual void MarkAsExpired();

core/include/userver/cache/caching_component_base.hpp

@@ -14,6 +14,7 @@
 #include <userver/cache/exceptions.hpp>
 #include <userver/compiler/demangle.hpp>
 #include <userver/components/component_base.hpp>
+#include <userver/components/component_context.hpp>
 #include <userver/components/component_fwd.hpp>
 #include <userver/concurrent/async_event_channel.hpp>
 #include <userver/dump/helpers.hpp>
@@ -36,9 +37,7 @@ namespace components {
 /// @brief Base class for caching components
 ///
 /// Provides facilities for creating periodically updated caches.
-/// You need to override cache::CacheUpdateTrait::Update
-/// then call cache::CacheUpdateTrait::StartPeriodicUpdates after setup
-/// and cache::CacheUpdateTrait::StopPeriodicUpdates before teardown.
+/// You need to override cache::CacheUpdateTrait::Update.
 /// You can also override cache::CachingComponentBase::PreAssignCheck and set
 /// has-pre-assign-check: true in the static config to enable check.
 ///
@@ -208,8 +207,6 @@ class CachingComponentBase : public ComponentBase, public cache::DataProvider<T>
     virtual void PreAssignCheck(const T* old_value_ptr, const T* new_value_ptr) const;
 
 private:
-    void OnAllComponentsLoaded() final;
-
     void Cleanup() final;
 
     void MarkAsExpired() final;
@@ -237,9 +234,7 @@ CachingComponentBase<T>::CachingComponentBase(const ComponentConfig& config, con
               }
           }
       )
-{
-    const auto initial_config = GetConfig();
-}
+{}
 
 template <typename T>
 CachingComponentBase<T>::~CachingComponentBase() {
@@ -356,11 +351,6 @@ std::unique_ptr<const T> CachingComponentBase<T>::ReadContents(dump::Reader& rea
     }
 }
 
-template <typename T>
-void CachingComponentBase<T>::OnAllComponentsLoaded() {
-    AssertPeriodicUpdateStarted();
-}
-
 template <typename T>
 void CachingComponentBase<T>::Cleanup() {
     cache_.Cleanup();

core/include/userver/components/statistics_storage.hpp

@@ -68,4 +68,21 @@ inline constexpr auto kConfigFileMode<StatisticsStorage> = ConfigFileMode::kNotR
 
 }  // namespace components
 
+namespace utils::statistics {
+
+/// @brief Add a writer function to @ref Storage from @ref StatisticsStorage.
+/// It automatically calls @ref Storage::RegisterWriter just after the component
+/// construction and @ref Entry::Unregister just before the component
+/// destructor.
+///
+/// @see @ref Storage::RegisterWriter.
+void RegisterWriterScope(
+    const components::ComponentContext&,
+    std::string common_prefix,
+    WriterFunc func,
+    std::vector<Label> add_labels = {}
+);
+
+}  // namespace utils::statistics
+
 USERVER_NAMESPACE_END

core/include/userver/dynamic_config/updater/component.hpp

@@ -75,8 +75,6 @@ class DynamicConfigClientUpdater final : public CachingComponentBase<dynamic_con
 
     DynamicConfigClientUpdater(const ComponentConfig&, const ComponentContext&);
 
-    ~DynamicConfigClientUpdater() override;
-
     // After calling this method, `Get()` will return a dynamic_config containing
     // the specified keys while the token that this method returned is alive.
     dynamic_config::AdditionalKeysToken SetAdditionalKeys(std::vector<std::string> keys);

core/include/userver/server/component.hpp

@@ -53,8 +53,6 @@ class Server final : public ComponentBase {
 
     Server(const components::ComponentConfig& component_config, const components::ComponentContext& component_context);
 
-    ~Server() override;
-
     void OnAllComponentsLoaded() override;
 
     void OnAllComponentsAreStopping() override;
@@ -71,8 +69,6 @@ class Server final : public ComponentBase {
     void WriteStatistics(utils::statistics::Writer& writer);
 
     std::unique_ptr<server::Server> server_;
-    utils::statistics::Entry server_statistics_holder_;
-    utils::statistics::Entry handler_statistics_holder_;
 };
 
 template <>

core/include/userver/utils/statistics/storage.hpp

@@ -146,6 +146,8 @@ class Storage final {
 
     /// @brief Add a writer function. Note that `func` is called concurrently with
     /// other code, so it should be thread-safe.
+    ///
+    /// @note Prefer using @ref RegisterWriterScope instead.
     Entry RegisterWriter(std::string common_prefix, WriterFunc func, std::vector<Label> add_labels = {});
 
     /// @deprecated Use RegisterWriter instead.

core/src/cache/cache_metrics_initialization_test.cpp

@@ -39,10 +39,10 @@ class ToyCache final : public components::CachingComponentBase<int> {
     ToyCache(const components::ComponentConfig& config, const components::ComponentContext& context)
         : CachingComponentBase(config, context)
     {
-        StartPeriodicUpdates();
+        EarlyStartPeriodicUpdates({});
     }
 
-    ~ToyCache() override { StopPeriodicUpdates(); }
+    ~ToyCache() override { EarlyStopPeriodicUpdates(); }
 
     void Update(
         cache::UpdateType /*type*/,