channels.hpp

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#pragma once
 
/// @file userver/ugrpc/client/channels.hpp
/// @brief Utilities for managing gRPC connections
 
#include <grpcpp/channel.h>
#include <grpcpp/completion_queue.h>
#include <grpcpp/security/credentials.h>
 
#include <userver/engine/deadline.hpp>
#include <userver/engine/task/task_processor_fwd.hpp>
 
#include <userver/ugrpc/client/impl/client_data.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace ugrpc::client {
 
namespace impl {
 
[[nodiscard]] bool TryWaitForConnected(
    grpc::Channel& channel,
    grpc::CompletionQueue& queue,
    engine::Deadline deadline,
    engine::TaskProcessor& blocking_task_processor
);
 
[[nodiscard]] bool TryWaitForConnected(
    impl::ChannelCache::Token& token,
    grpc::CompletionQueue& queue,
    engine::Deadline deadline,
    engine::TaskProcessor& blocking_task_processor
);
 
}  // namespace impl
 
/// @brief Create a new gRPC channel (connection pool) for the endpoint
///
/// Channel creation is expensive, reuse channels if possible.
///
/// Each channel is fully thread-safe: it can be used across multiple threads,
/// possibly from multiple clients and using multiple `CompletionQueue`
/// instances at the same time.
///
/// @param blocking_task_processor task processor for blocking channel creation
/// @param channel_credentials channel credentials
/// @param endpoint string host:port
/// @returns shared pointer to the gRPC channel
std::shared_ptr<grpc::Channel> MakeChannel(
    engine::TaskProcessor& blocking_task_processor,
    std::shared_ptr<grpc::ChannelCredentials> channel_credentials,
    const std::string& endpoint
);
 
/// @brief Wait until the channel state of `client` is `READY`. If the current
/// state is already `READY`, returns `true` immediately. In case of multiple
/// underlying channels, waits for all of them.
/// @returns `true` if the state changed before `deadline` expired
/// @note The wait operation does not support task cancellations
template <typename Client>
[[nodiscard]] bool
TryWaitForConnected(Client& client, engine::Deadline deadline, engine::TaskProcessor& blocking_task_processor) {
    return impl::TryWaitForConnected(
        impl::GetClientData(client).GetChannelToken(),
        impl::GetClientData(client).NextQueue(),
        deadline,
        blocking_task_processor
    );
}
 
}  // namespace ugrpc::client
 
USERVER_NAMESPACE_END