grpc/include/grpcpp/server.h

//
//
// Copyright 2015 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//

#ifndef GRPCPP_SERVER_H
#define GRPCPP_SERVER_H

#include <list>
#include <memory>
#include <vector>

#include <grpc/compression.h>
#include <grpc/support/atm.h>
#include <grpc/support/port_platform.h>
#include <grpcpp/channel.h>
#include <grpcpp/completion_queue.h>
#include <grpcpp/health_check_service_interface.h>
#include <grpcpp/impl/call.h>
#include <grpcpp/impl/grpc_library.h>
#include <grpcpp/impl/rpc_service_method.h>
#include <grpcpp/security/server_credentials.h>
#include <grpcpp/server_interface.h>
#include <grpcpp/support/channel_arguments.h>
#include <grpcpp/support/client_interceptor.h>
#include <grpcpp/support/config.h>
#include <grpcpp/support/status.h>

struct grpc_server;

namespace grpc {
class AsyncGenericService;
class ServerContext;
class ServerInitializer;

namespace internal {
class ExternalConnectionAcceptorImpl;
}  // namespace internal

/// Represents a gRPC server.
///
/// Use a \a grpc::ServerBuilder to create, configure, and start
/// \a Server instances.
class Server : public ServerInterface, private internal::GrpcLibrary {
 public:
  ~Server() ABSL_LOCKS_EXCLUDED(mu_) override;

  /// Block until the server shuts down.
  ///
  /// \warning The server must be either shutting down or some other thread must
  /// call \a Shutdown for this function to ever return.
  void Wait() ABSL_LOCKS_EXCLUDED(mu_) override;

  /// Global callbacks are a set of hooks that are called when server
  /// events occur.  \a SetGlobalCallbacks method is used to register
  /// the hooks with gRPC.  Note that
  /// the \a GlobalCallbacks instance will be shared among all
  /// \a Server instances in an application and can be set exactly
  /// once per application.
  class GlobalCallbacks {
   public:
    virtual ~GlobalCallbacks() {}
    /// Called before server is created.
    virtual void UpdateArguments(ChannelArguments* /*args*/) {}
    /// Called before application callback for each synchronous server request
    virtual void PreSynchronousRequest(ServerContext* context) = 0;
    /// Called after application callback for each synchronous server request
    virtual void PostSynchronousRequest(ServerContext* context) = 0;
    /// Called before server is started.
    virtual void PreServerStart(Server* /*server*/) {}
    /// Called after a server port is added.
    virtual void AddPort(Server* /*server*/, const std::string& /*addr*/,
                         ServerCredentials* /*creds*/, int /*port*/) {}
  };
  /// Set the global callback object. Can only be called once per application.
  /// Does not take ownership of callbacks, and expects the pointed to object
  /// to be alive until all server objects in the process have been destroyed.
  /// The same \a GlobalCallbacks object will be used throughout the
  /// application and is shared among all \a Server objects.
  static void SetGlobalCallbacks(GlobalCallbacks* callbacks);

  /// Returns a \em raw pointer to the underlying \a grpc_server instance.
  /// EXPERIMENTAL:  for internal/test use only
  grpc_server* c_server();

  /// Returns the health check service.
  HealthCheckServiceInterface* GetHealthCheckService() const {
    return health_check_service_.get();
  }

  /// Establish a channel for in-process communication
  std::shared_ptr<Channel> InProcessChannel(const ChannelArguments& args);

  /// NOTE: class experimental_type is not part of the public API of this class.
  /// TODO(yashykt): Integrate into public API when this is no longer
  /// experimental.
  class experimental_type {
   public:
    explicit experimental_type(Server* server) : server_(server) {}

    /// Establish a channel for in-process communication with client
    /// interceptors
    std::shared_ptr<Channel> InProcessChannelWithInterceptors(
        const ChannelArguments& args,
        std::vector<
            std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>
            interceptor_creators);

   private:
    Server* server_;
  };

  /// NOTE: The function experimental() is not stable public API. It is a view
  /// to the experimental components of this class. It may be changed or removed
  /// at any time.
  experimental_type experimental() { return experimental_type(this); }

 protected:
  /// Register a service. This call does not take ownership of the service.
  /// The service must exist for the lifetime of the Server instance.
  bool RegisterService(const std::string* addr, Service* service) override;

  /// Try binding the server to the given \a addr endpoint
  /// (port, and optionally including IP address to bind to).
  ///
  /// It can be invoked multiple times. Should be used before
  /// starting the server.
  ///
  /// \param addr The address to try to bind to the server (eg, localhost:1234,
  /// 192.168.1.1:31416, [::1]:27182, etc.).
  /// \param creds The credentials associated with the server.
  ///
  /// \return bound port number on success, 0 on failure.
  ///
  /// \warning It is an error to call this method on an already started server.
  int AddListeningPort(const std::string& addr,
                       ServerCredentials* creds) override;

  /// NOTE: This is *NOT* a public API. The server constructors are supposed to
  /// be used by \a ServerBuilder class only. The constructor will be made
  /// 'private' very soon.
  ///
  /// Server constructors. To be used by \a ServerBuilder only.
  ///
  /// \param args The channel args
  ///
  /// \param sync_server_cqs The completion queues to use if the server is a
  /// synchronous server (or a hybrid server). The server polls for new RPCs on
  /// these queues
  ///
  /// \param min_pollers The minimum number of polling threads per server
  /// completion queue (in param sync_server_cqs) to use for listening to
  /// incoming requests (used only in case of sync server)
  ///
  /// \param max_pollers The maximum number of polling threads per server
  /// completion queue (in param sync_server_cqs) to use for listening to
  /// incoming requests (used only in case of sync server)
  ///
  /// \param sync_cq_timeout_msec The timeout to use when calling AsyncNext() on
  /// server completion queues passed via sync_server_cqs param.
  Server(ChannelArguments* args,
         std::shared_ptr<std::vector<std::unique_ptr<ServerCompletionQueue>>>
             sync_server_cqs,
         int min_pollers, int max_pollers, int sync_cq_timeout_msec,
         std::vector<std::shared_ptr<internal::ExternalConnectionAcceptorImpl>>
             acceptors,
         grpc_server_config_fetcher* server_config_fetcher = nullptr,
         grpc_resource_quota* server_rq = nullptr,
         std::vector<
             std::unique_ptr<experimental::ServerInterceptorFactoryInterface>>
             interceptor_creators = std::vector<std::unique_ptr<
                 experimental::ServerInterceptorFactoryInterface>>(),
         experimental::ServerMetricRecorder* server_metric_recorder = nullptr);

  /// Start the server.
  ///
  /// \param cqs Completion queues for handling asynchronous services. The
  /// caller is required to keep all completion queues live until the server is
  /// destroyed.
  /// \param num_cqs How many completion queues does \a cqs hold.
  void Start(ServerCompletionQueue** cqs, size_t num_cqs) override;

  grpc_server* server() override { return server_; }

  /// NOTE: This method is not part of the public API for this class.
  void set_health_check_service(
      std::unique_ptr<HealthCheckServiceInterface> service) {
    health_check_service_ = std::move(service);
  }

  ContextAllocator* context_allocator() { return context_allocator_.get(); }

  /// NOTE: This method is not part of the public API for this class.
  bool health_check_service_disabled() const {
    return health_check_service_disabled_;
  }

 private:
  std::vector<std::unique_ptr<experimental::ServerInterceptorFactoryInterface>>*
  interceptor_creators() override {
    return &interceptor_creators_;
  }

  friend class AsyncGenericService;
  friend class ServerBuilder;
  friend class ServerInitializer;

  class SyncRequest;
  class CallbackRequestBase;
  template <class ServerContextType>
  class CallbackRequest;
  class UnimplementedAsyncRequest;
  class UnimplementedAsyncResponse;

  /// SyncRequestThreadManager is an implementation of ThreadManager. This class
  /// is responsible for polling for incoming RPCs and calling the RPC handlers.
  /// This is only used in case of a Sync server (i.e a server exposing a sync
  /// interface)
  class SyncRequestThreadManager;

  /// Register a generic service. This call does not take ownership of the
  /// service. The service must exist for the lifetime of the Server instance.
  void RegisterAsyncGenericService(AsyncGenericService* service) override;

  /// Register a callback-based generic service. This call does not take
  /// ownership of theservice. The service must exist for the lifetime of the
  /// Server instance.
  void RegisterCallbackGenericService(CallbackGenericService* service) override;

  void RegisterContextAllocator(
      std::unique_ptr<ContextAllocator> context_allocator) {
    context_allocator_ = std::move(context_allocator);
  }

  void PerformOpsOnCall(internal::CallOpSetInterface* ops,
                        internal::Call* call) override;

  void ShutdownInternal(gpr_timespec deadline)
      ABSL_LOCKS_EXCLUDED(mu_) override;

  int max_receive_message_size() const override {
    return max_receive_message_size_;
  }

  bool call_metric_recording_enabled() const override {
    return call_metric_recording_enabled_;
  }

  experimental::ServerMetricRecorder* server_metric_recorder() const override {
    return server_metric_recorder_;
  }

  CompletionQueue* CallbackCQ() ABSL_LOCKS_EXCLUDED(mu_) override;

  ServerInitializer* initializer();

  // Functions to manage the server shutdown ref count. Things that increase
  // the ref count are the running state of the server (take a ref at start and
  // drop it at shutdown) and each running callback RPC.
  void Ref();
  void UnrefWithPossibleNotify() ABSL_LOCKS_EXCLUDED(mu_);
  void UnrefAndWaitLocked() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);

  std::vector<std::shared_ptr<internal::ExternalConnectionAcceptorImpl>>
      acceptors_;

  // A vector of interceptor factory objects.
  // This should be destroyed after health_check_service_ and this requirement
  // is satisfied by declaring interceptor_creators_ before
  // health_check_service_. (C++ mandates that member objects be destroyed in
  // the reverse order of initialization.)
  std::vector<std::unique_ptr<experimental::ServerInterceptorFactoryInterface>>
      interceptor_creators_;

  int max_receive_message_size_;

  /// The following completion queues are ONLY used in case of Sync API
  /// i.e. if the server has any services with sync methods. The server uses
  /// these completion queues to poll for new RPCs
  std::shared_ptr<std::vector<std::unique_ptr<ServerCompletionQueue>>>
      sync_server_cqs_;

  /// List of \a ThreadManager instances (one for each cq in
  /// the \a sync_server_cqs)
  std::vector<std::unique_ptr<SyncRequestThreadManager>> sync_req_mgrs_;

  // Server status
  internal::Mutex mu_;
  bool started_;
  bool shutdown_ ABSL_GUARDED_BY(mu_);
  bool shutdown_notified_
      ABSL_GUARDED_BY(mu_);  // Was notify called on the shutdown_cv_
  internal::CondVar shutdown_done_cv_;
  bool shutdown_done_ ABSL_GUARDED_BY(mu_) = false;
  std::atomic_int shutdown_refs_outstanding_{1};

  internal::CondVar shutdown_cv_;

  std::shared_ptr<GlobalCallbacks> global_callbacks_;

  std::vector<std::string> services_;
  bool has_async_generic_service_ = false;
  bool has_callback_generic_service_ = false;
  bool has_callback_methods_ = false;

  // Pointer to the wrapped grpc_server.
  grpc_server* server_;

  std::unique_ptr<ServerInitializer> server_initializer_;

  std::unique_ptr<ContextAllocator> context_allocator_;

  std::unique_ptr<HealthCheckServiceInterface> health_check_service_;
  bool health_check_service_disabled_;

  // When appropriate, use a default callback generic service to handle
  // unimplemented methods
  std::unique_ptr<CallbackGenericService> unimplemented_service_;

  // A special handler for resource exhausted in sync case
  std::unique_ptr<internal::MethodHandler> resource_exhausted_handler_;

  // Handler for callback generic service, if any
  std::unique_ptr<internal::MethodHandler> generic_handler_;

  // callback_cq_ references the callbackable completion queue associated
  // with this server (if any). It is set on the first call to CallbackCQ().
  // It is _not owned_ by the server; ownership belongs with its internal
  // shutdown callback tag (invoked when the CQ is fully shutdown).
  std::atomic<CompletionQueue*> callback_cq_{nullptr};

  // List of CQs passed in by user that must be Shutdown only after Server is
  // Shutdown.  Even though this is only used with NDEBUG, instantiate it in all
  // cases since otherwise the size will be inconsistent.
  std::vector<CompletionQueue*> cq_list_;

  // Whetner per-call load reporting is enabled.
  bool call_metric_recording_enabled_ = false;

  // Interface to read or update server-wide metrics. Optional.
  experimental::ServerMetricRecorder* server_metric_recorder_ = nullptr;
};

}  // namespace grpc

#endif  // GRPCPP_SERVER_H