ugrpc::server::MiddlewareCallContext Class Reference

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Table of Contents

• Detailed Description
• Public Member Functions
• Member Function Documentation
• GetServerContext()
• GetStorageContext()
• Example usage:
• IsClientStreaming()
• IsServerStreaming()
• SetError()

#include <userver/ugrpc/server/middlewares/base.hpp>

Detailed Description

Context for middleware-specific data during gRPC call.

Examples

samples/grpc_middleware_service/src/middlewares/server/auth.cpp, samples/grpc_middleware_service/src/middlewares/server/auth.hpp, samples/grpc_middleware_service/src/middlewares/server/meta_filter.cpp, and samples/grpc_middleware_service/src/middlewares/server/meta_filter.hpp.

Definition at line 43 of file base.hpp.

Inheritance diagram for ugrpc::server::MiddlewareCallContext:

Public Member Functions
void	SetError (grpc::Status &&status) noexcept
	Aborts the RPC, returning the specified status to the upstream client, see details below.
bool	IsClientStreaming () const noexcept
bool	IsServerStreaming () const noexcept
const dynamic_config::Snapshot &	GetInitialDynamicConfig () const
	Get values extracted from dynamic_config. Snapshot will be deleted when the last middleware completes.
grpc::ServerContext &	GetServerContext ()
std::string_view	GetCallName () const
	Name of the RPC in the format full.path.ServiceName/MethodName
std::string_view	GetServiceName () const
	Get name of gRPC service.
std::string_view	GetMethodName () const
	Get name of called gRPC method.
tracing::Span &	GetSpan ()
	Get the span of the current RPC.
utils::AnyStorage< StorageContext > &	GetStorageContext ()
	Returns call context for storing per-call custom data.

Member Function Documentation

GetServerContext()

grpc::ServerContext & ugrpc::server::CallContextBase::GetServerContext ( )

inherited

Returns

the ServerContext used for this RPC

Examples

samples/grpc_middleware_service/src/middlewares/server/auth.cpp, and samples/grpc_middleware_service/src/middlewares/server/meta_filter.cpp.

GetStorageContext()

utils::AnyStorage< StorageContext > & ugrpc::server::CallContextBase::GetStorageContext ( )

inherited

Returns call context for storing per-call custom data.

The context can be used to pass data from server middleware to client handler or from one middleware to another one.

Example usage:

In authentication middleware:

if (password_is_correct) {
  // Username is authenticated, set it in per-call storage context
  context.GetStorageContext().Emplace(kAuthUsername, username);
}

In client handler:

const auto& username = context.GetStorageContext().Get(kAuthUsername);
auto msg = fmt::format("Hello, {}!", username);

IsClientStreaming()

bool ugrpc::server::MiddlewareCallContext::IsClientStreaming ( ) const

noexcept

Returns

Is a client-side streaming call

IsServerStreaming()

bool ugrpc::server::MiddlewareCallContext::IsServerStreaming ( ) const

noexcept

Returns

Is a server-side streaming call

SetError()

void ugrpc::server::MiddlewareCallContext::SetError ( grpc::Status && status )

noexcept

Aborts the RPC, returning the specified status to the upstream client, see details below.

It should be the last command in middlewares hooks.

If that method is called in methods:

1. MiddlewareBase::OnCallStart - remaining OnCallStart hooks won't be called. Will be called OnCallFinish hooks of middlewares that was called before SetError
2. MiddlewareBase::PostRecvMessage or ugrpc::server::MiddlewareBase::PreSendMessage :
   • unary: handler won't be called - all. All OnCallFinish hooks will be called.
   • stream: from Read/Write throws a special exception, that ends a handler. All OnCallFinish hooks will be called.
3. MiddlewareBase::OnCallFinish - all OnCallFinish will be called, despite of SetError and exceptions. If the request is going to end with the error status, then the status is replaced with the status of the current hook.

Example usage

Middleware::Middleware() = default;
 
void Middleware::OnCallStart(ugrpc::server::MiddlewareCallContext& context) const {
    const auto& metadata = context.GetServerContext().client_metadata();
 
    auto it = metadata.find(kKey);
 
    if (it == metadata.cend() || it->second != kCredentials) {
        LOG_ERROR() << "Invalid credentials";
        return context.SetError(::grpc::Status{::grpc::StatusCode::PERMISSION_DENIED, "Invalid credentials"});
    }
}

Examples

samples/grpc_middleware_service/src/middlewares/server/auth.cpp, and samples/grpc_middleware_service/src/middlewares/server/meta_filter.cpp.

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The documentation for this class was generated from the following file:

• userver/ugrpc/server/middlewares/base.hpp