base.hpp

#pragma once
 
/// @file userver/ugrpc/client/middlewares/middleware_base.hpp
/// @brief @copybrief ugrpc::client::MiddlewareBase
 
#include <memory>
#include <vector>
 
#include <userver/components/component_base.hpp>
 
#include <userver/ugrpc/client/middlewares/fwd.hpp>
#include <userver/ugrpc/client/rpc.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace ugrpc::client {
 
/// @brief Context for middleware-specific data during gRPC call
///
/// It is created for each gRPC Call and it stores aux. data
/// used by middlewares. Each registered middleware is called by
/// `Middleware::Handle` with the context passed as an argument.
/// A middleware may access Call and initial request (if any) using the context.
class MiddlewareCallContext final {
public:
    /// @cond
    explicit MiddlewareCallContext(impl::RpcData& data);
    /// @endcond
 
    /// @returns the `ClientContext` used for this RPC
    grpc::ClientContext& GetContext() noexcept;
 
    /// @returns client name
    std::string_view GetClientName() const noexcept;
 
    /// @returns RPC name
    std::string_view GetCallName() const noexcept;
 
    /// @returns RPC kind
    CallKind GetCallKind() const noexcept;
 
    /// @returns RPC span
    tracing::Span& GetSpan() noexcept;
 
    /// @cond
    // For internal use only
    impl::RpcData& GetData(ugrpc::impl::InternalTag);
    /// @endcond
 
private:
    impl::RpcData& data_;
};
 
/// @ingroup userver_base_classes
///
/// @brief Base class for client gRPC middleware
class MiddlewareBase {
public:
    virtual ~MiddlewareBase();
 
    MiddlewareBase(const MiddlewareBase&) = delete;
    MiddlewareBase(MiddlewareBase&&) = delete;
 
    MiddlewareBase& operator=(const MiddlewareBase&) = delete;
    MiddlewareBase& operator=(MiddlewareBase&&) = delete;
 
    /// @brief This function is called before rpc, on each rpc. It does nothing by
    /// default
    virtual void PreStartCall(MiddlewareCallContext&) const;
 
    /// @brief This function is called before sending message, on each request. It
    /// does nothing by default
    /// @note  Not called for `GenericClient` messages
    virtual void PreSendMessage(MiddlewareCallContext&, const google::protobuf::Message&) const;
 
    /// @brief This function is called after receiving message, on each response.
    /// It does nothing by default
    /// @note  Not called for `GenericClient` messages
    virtual void PostRecvMessage(MiddlewareCallContext&, const google::protobuf::Message&) const;
 
    /// @brief This function is called after rpc, on each rpc. It does nothing by
    /// default
    /// @note Could be not called in case of deadline or network problem
    /// @see @ref RpcInterruptedError
    virtual void PostFinish(MiddlewareCallContext&, const grpc::Status&) const;
 
protected:
    MiddlewareBase();
};
 
/// @ingroup userver_base_classes
///
/// @brief Factory that creates specific client middlewares for clients
class MiddlewareFactoryBase {
public:
    virtual ~MiddlewareFactoryBase();
 
    virtual std::shared_ptr<const MiddlewareBase> GetMiddleware(std::string_view client_name) const = 0;
};
 
using MiddlewareFactories = std::vector<std::shared_ptr<const MiddlewareFactoryBase>>;
 
/// @ingroup userver_base_classes
///
/// @brief Base class for client middleware component
class MiddlewareComponentBase : public components::ComponentBase {
    using components::ComponentBase::ComponentBase;
 
public:
    /// @brief Returns a middleware according to the component's settings
    virtual std::shared_ptr<const MiddlewareFactoryBase> GetMiddlewareFactory() = 0;
};
 
namespace impl {
 
Middlewares InstantiateMiddlewares(const MiddlewareFactories& factories, const std::string& client_name);
 
}  // namespace impl
 
}  // namespace ugrpc::client
 
USERVER_NAMESPACE_END