1 // 2 // 3 // Copyright 2015 gRPC authors. 4 // 5 // Licensed under the Apache License, Version 2.0 (the "License"); 6 // you may not use this file except in compliance with the License. 7 // You may obtain a copy of the License at 8 // 9 // http://www.apache.org/licenses/LICENSE-2.0 10 // 11 // Unless required by applicable law or agreed to in writing, software 12 // distributed under the License is distributed on an "AS IS" BASIS, 13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 // See the License for the specific language governing permissions and 15 // limitations under the License. 16 // 17 // 18 19 /// An Alarm posts the user-provided tag to its associated completion queue or 20 /// invokes the user-provided function on expiry or cancellation. 21 #ifndef GRPCPP_ALARM_H 22 #define GRPCPP_ALARM_H 23 24 #include <functional> 25 26 #include <grpc/event_engine/event_engine.h> 27 #include <grpc/grpc.h> 28 #include <grpcpp/completion_queue.h> 29 #include <grpcpp/impl/completion_queue_tag.h> 30 #include <grpcpp/impl/grpc_library.h> 31 #include <grpcpp/support/time.h> 32 33 namespace grpc { 34 35 /// Trigger a \a CompletionQueue event, or asynchronous callback execution, 36 /// after some deadline. 37 /// 38 /// The \a Alarm API has separate \a Set methods for CompletionQueues and 39 /// callbacks, but only one can be used at any given time. After an alarm has 40 /// been triggered or cancelled, the same Alarm object may reused. 41 /// 42 /// Alarm methods are not thread-safe. Applications must ensure a strict 43 /// ordering between calls to \a Set and \a Cancel. This also implies that any 44 /// cancellation that occurs before the alarm has been set will have no effect 45 /// on any future \a Set calls. 46 class Alarm : private grpc::internal::GrpcLibrary { 47 public: 48 /// Create an unset Alarm. 49 Alarm(); 50 51 /// Destroy the given completion queue alarm, cancelling it in the process. 52 ~Alarm() override; 53 54 /// DEPRECATED: Create and set a completion queue alarm instance associated to 55 /// \a cq. 56 /// This form is deprecated because it is inherently racy. 57 /// \internal We rely on the presence of \a cq for grpc initialization. If \a 58 /// cq were ever to be removed, a reference to a static 59 /// internal::GrpcLibraryInitializer instance would need to be introduced 60 /// here. \endinternal. 61 template <typename T> Alarm(grpc::CompletionQueue * cq,const T & deadline,void * tag)62 Alarm(grpc::CompletionQueue* cq, const T& deadline, void* tag) : Alarm() { 63 SetInternal(cq, grpc::TimePoint<T>(deadline).raw_time(), tag); 64 } 65 66 /// Trigger an alarm instance on completion queue \a cq at the specified time. 67 /// Once the alarm expires (at \a deadline) or it's cancelled (see \a Cancel), 68 /// an event with tag \a tag will be added to \a cq. If the alarm expired, the 69 /// event's success bit will be true, false otherwise (ie, upon cancellation). 70 // 71 // USAGE NOTE: This is frequently used to inject arbitrary tags into \a cq by 72 // setting an immediate deadline. Such usage allows synchronizing an external 73 // event with an application's \a grpc::CompletionQueue::Next loop. 74 template <typename T> Set(grpc::CompletionQueue * cq,const T & deadline,void * tag)75 void Set(grpc::CompletionQueue* cq, const T& deadline, void* tag) { 76 SetInternal(cq, grpc::TimePoint<T>(deadline).raw_time(), tag); 77 } 78 79 /// Alarms aren't copyable. 80 Alarm(const Alarm&) = delete; 81 Alarm& operator=(const Alarm&) = delete; 82 83 /// Alarms are movable. Alarm(Alarm && rhs)84 Alarm(Alarm&& rhs) noexcept : alarm_(rhs.alarm_) { rhs.alarm_ = nullptr; } 85 Alarm& operator=(Alarm&& rhs) noexcept { 86 std::swap(alarm_, rhs.alarm_); 87 return *this; 88 } 89 90 /// Cancel a completion queue alarm. Calling this function over an alarm that 91 /// has already fired has no effect. 92 void Cancel(); 93 94 /// Set an alarm to invoke callback \a f. The argument to the callback 95 /// states whether the alarm expired at \a deadline (true) or was cancelled 96 /// (false) 97 template <typename T> Set(const T & deadline,std::function<void (bool)> f)98 void Set(const T& deadline, std::function<void(bool)> f) { 99 SetInternal(grpc::TimePoint<T>(deadline).raw_time(), std::move(f)); 100 } 101 102 private: 103 void SetInternal(grpc::CompletionQueue* cq, gpr_timespec deadline, void* tag); 104 void SetInternal(gpr_timespec deadline, std::function<void(bool)> f); 105 106 grpc::internal::CompletionQueueTag* alarm_; 107 }; 108 109 } // namespace grpc 110 111 #endif // GRPCPP_ALARM_H 112