configuration.hpp

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#pragma once
 
/// @file userver/server/middlewares/configuration.hpp
/// @brief Utility functions/classes for middleware pipelines configuration
 
#include <string>
#include <vector>
 
#include <userver/components/component_base.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace components {
class ComponentList;
}
 
namespace server::middlewares {
 
/// @ingroup userver_middlewares
///
/// @brief Returns a list of middleware-components which userver uses by
/// default in http server.
///
/// The list contains a bunch of middlewares into which most of
/// http-handler functionality is split (metrics, tracing, deadline-propagation
/// etc. etc.)
components::ComponentList DefaultMiddlewareComponents();
 
/// @ingroup userver_middlewares
///
/// @brief Returns a list of middleware-components required by userver to start
/// a http server.
///
/// Components in this list don't have any useful functionality, they are
/// just infrastructure.
components::ComponentList MinimalMiddlewareComponents();
 
using MiddlewaresList = std::vector<std::string>;
 
/// @ingroup userver_middlewares
///
/// @brief Returns the default userver-provided middleware pipeline.
MiddlewaresList DefaultPipeline();
 
/// @ingroup userver_middlewares userver_base_classes
///
/// @brief Base class to build a server-wide middleware pipeline.
/// One may inherit from it and implement any custom logic, if desired.
class PipelineBuilder : public components::ComponentBase {
public:
    static constexpr std::string_view kName{"default-server-middleware-pipeline-builder"};
 
    PipelineBuilder(const components::ComponentConfig&, const components::ComponentContext&);
 
    /// @brief The method to build a server-wide middleware pipeline,
    /// one may override it if custom behavior is desired.
    /// @param userver_middleware_pipeline default userver-provided middleware
    /// pipeline
    ///
    /// @note We recommend against omitting/modifying default userver pipeline,
    /// but leave a possibility to do so.
    virtual MiddlewaresList BuildPipeline(MiddlewaresList userver_middleware_pipeline) const {
        auto& resulting_pipeline = userver_middleware_pipeline;
        const auto& middlewares_to_append = GetMiddlewaresToAppend();
 
        resulting_pipeline.insert(resulting_pipeline.end(), middlewares_to_append.begin(), middlewares_to_append.end());
 
        return resulting_pipeline;
    }
 
    static yaml_config::Schema GetStaticConfigSchema();
 
protected:
    const MiddlewaresList& GetMiddlewaresToAppend() const;
 
private:
    MiddlewaresList middlewares_to_append_;
};
 
/// @ingroup userver_middlewares userver_base_classes
///
/// @brief Base class to build a per-handler middleware pipeline.
/// One may inherit from it and implement any custom logic, if desired.
/// By default the behavior is to use the server-wide pipeline.
class HandlerPipelineBuilder : public components::ComponentBase {
public:
    static constexpr std::string_view kName{"default-handler-middleware-pipeline-builder"};
 
    HandlerPipelineBuilder(const components::ComponentConfig&, const components::ComponentContext&);
 
    /// @brief The method to configure build a per-handler middleware pipeline,
    /// one may override it if custom behavior is desired.
    ///
    /// For example, a ping/ handler doesn't necessary need any business-logic
    /// related functionality, and could use just DefaultPipeline() for itself.
    ///
    /// @param server_middleware_pipeline the server-wide middleware pipeline
    virtual MiddlewaresList BuildPipeline(MiddlewaresList server_middleware_pipeline) const {
        return server_middleware_pipeline;
    }
};
 
}  // namespace server::middlewares
 
template <>
inline constexpr bool components::kHasValidate<server::middlewares::PipelineBuilder> = true;
 
template <>
inline constexpr auto components::kConfigFileMode<server::middlewares::PipelineBuilder> = ConfigFileMode::kNotRequired;
 
template <>
inline constexpr bool components::kHasValidate<server::middlewares::HandlerPipelineBuilder> = true;
 
template <>
inline constexpr auto components::kConfigFileMode<server::middlewares::HandlerPipelineBuilder> =
    ConfigFileMode::kNotRequired;
 
USERVER_NAMESPACE_END