component_base.hpp

Go to the documentation of this file.

#pragma once
 
/// @file userver/components/component_base.hpp
/// @brief Contains components::ComponentBase declaration and forward
/// declarations of components::ComponentConfig and
/// components::ComponentContext, function components::GetCurrentComponentName()
 
#include <userver/components/component_fwd.hpp>
#include <userver/components/raw_component_base.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace components {
 
/// @ingroup userver_base_classes
///
/// @brief Base class for all @ref userver_components "application components",
/// it depends on components::Logger and components::Tracer.
class ComponentBase : public RawComponentBase {
public:
    ComponentBase(const ComponentConfig&, const ComponentContext&);
 
    ComponentBase(ComponentBase&&) = delete;
    ComponentBase(const ComponentBase&) = delete;
 
    /// It is a good place to stop your work here.
    /// All components dependent on the current component were destroyed.
    /// All components on which the current component depends are still alive.
    ~ComponentBase() override = default;
 
    /// Override this function to inform the world of the state of your
    /// component.
    ///
    /// @warning The function is called concurrently from multiple threads.
    ComponentHealth GetComponentHealth() const override { return ComponentHealth::kOk; }
 
    /// Called once if the creation of any other component failed.
    /// If the current component expects some other component to take any action
    /// with the current component, this call is a signal that such action may
    /// never happen due to components loading was cancelled.
    /// Application components might not want to override it.
    void OnLoadingCancelled() override {}
 
    /// Component may use this function to finalize registration of other
    /// components that depend on it (for example, handler components register
    /// in server component, and the latter uses OnAllComponentsLoaded() to start
    /// processing requests).
    ///
    /// Base components may override it and make `final` to do some work after the
    /// derived object constructor is called. Don't use it otherwise.
    void OnAllComponentsLoaded() override {}
 
    /// Serving components like HTTP and gRPC servers may use this function to stop accepting new requests
    /// and shutdown serving in the given time interval.
    /// Application components likely do not need to override it.
    ///
    /// @param[in] serving_shutdown_deadline The deadline until already running requests should be allowed
    /// to complete.
    /// The component is supposed to stop accepting new requests and continue processing of already
    /// active requests until this deadline (unless those requests finish earlier).
    /// And it might completely shutdown requests processing when the deadline is reached
    /// (or when no active requests left).
    void OnGracefulShutdown(engine::Deadline /*serving_shutdown_deadline*/) override;
 
    /// Component may use this function to stop doing work before the stop of the
    /// components that depend on it.
    ///
    /// Base components may override it and make `final` to do some work before
    /// the derived object constructor is called. Don't use it otherwise.
    void OnAllComponentsAreStopping() override {}
 
    /// If the component pulls more options from @ref components::ComponentConfig than its
    /// parent component, then it needs to define `GetStaticConfigSchema` method
    /// and add its own options to the parent component's options.
    static yaml_config::Schema GetStaticConfigSchema();
 
protected:
    /// @deprecated use @ref components::ComponentBase instead.
    using LoggableComponentBase = ComponentBase;
};
 
/// @deprecated use @ref components::ComponentBase instead.
using LoggableComponentBase = ComponentBase;
 
/// @see @ref components::LocateDependency
template <typename T>
struct WithType {};
 
}  // namespace components
 
USERVER_NAMESPACE_END