1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc. All rights reserved.
3// https://developers.google.com/protocol-buffers/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are
7// met:
8//
9// * Redistributions of source code must retain the above copyright
10// notice, this list of conditions and the following disclaimer.
11// * Redistributions in binary form must reproduce the above
12// copyright notice, this list of conditions and the following disclaimer
13// in the documentation and/or other materials provided with the
14// distribution.
15// * Neither the name of Google Inc. nor the names of its
16// contributors may be used to endorse or promote products derived from
17// this software without specific prior written permission.
18//
19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31// Author: kenton@google.com (Kenton Varda)
32// Based on original Protocol Buffers design by
33// Sanjay Ghemawat, Jeff Dean, and others.
34//
35// DEPRECATED: This module declares the abstract interfaces underlying proto2
36// RPC services. These are intended to be independent of any particular RPC
37// implementation, so that proto2 services can be used on top of a variety
38// of implementations. Starting with version 2.3.0, RPC implementations should
39// not try to build on these, but should instead provide code generator plugins
40// which generate code specific to the particular RPC implementation. This way
41// the generated code can be more appropriate for the implementation in use
42// and can avoid unnecessary layers of indirection.
43//
44//
45// When you use the protocol compiler to compile a service definition, it
46// generates two classes: An abstract interface for the service (with
47// methods matching the service definition) and a "stub" implementation.
48// A stub is just a type-safe wrapper around an RpcChannel which emulates a
49// local implementation of the service.
50//
51// For example, the service definition:
52// service MyService {
53// rpc Foo(MyRequest) returns(MyResponse);
54// }
55// will generate abstract interface "MyService" and class "MyService::Stub".
56// You could implement a MyService as follows:
57// class MyServiceImpl : public MyService {
58// public:
59// MyServiceImpl() {}
60// ~MyServiceImpl() {}
61//
62// // implements MyService ---------------------------------------
63//
64// void Foo(google::protobuf::RpcController* controller,
65// const MyRequest* request,
66// MyResponse* response,
67// Closure* done) {
68// // ... read request and fill in response ...
69// done->Run();
70// }
71// };
72// You would then register an instance of MyServiceImpl with your RPC server
73// implementation. (How to do that depends on the implementation.)
74//
75// To call a remote MyServiceImpl, first you need an RpcChannel connected to it.
76// How to construct a channel depends, again, on your RPC implementation.
77// Here we use a hypothetical "MyRpcChannel" as an example:
78// MyRpcChannel channel("rpc:hostname:1234/myservice");
79// MyRpcController controller;
80// MyServiceImpl::Stub stub(&channel);
81// FooRequest request;
82// FooResponse response;
83//
84// // ... fill in request ...
85//
86// stub.Foo(&controller, request, &response, NewCallback(HandleResponse));
87//
88// On Thread-Safety:
89//
90// Different RPC implementations may make different guarantees about what
91// threads they may run callbacks on, and what threads the application is
92// allowed to use to call the RPC system. Portable software should be ready
93// for callbacks to be called on any thread, but should not try to call the
94// RPC system from any thread except for the ones on which it received the
95// callbacks. Realistically, though, simple software will probably want to
96// use a single-threaded RPC system while high-end software will want to
97// use multiple threads. RPC implementations should provide multiple
98// choices.
99
100#ifndef GOOGLE_PROTOBUF_SERVICE_H__
101#define GOOGLE_PROTOBUF_SERVICE_H__
102
103
104#include <string>
105#include <google/protobuf/stubs/callback.h>
106#include <google/protobuf/stubs/common.h>
107
108#ifdef SWIG
109#error "You cannot SWIG proto headers"
110#endif
111
112// Must be included last.
113#include <google/protobuf/port_def.inc>
114
115namespace google {
116namespace protobuf {
117
118// Defined in this file.
119class Service;
120class RpcController;
121class RpcChannel;
122
123// Defined in other files.
124class Descriptor; // descriptor.h
125class ServiceDescriptor; // descriptor.h
126class MethodDescriptor; // descriptor.h
127class Message; // message.h
128
129// Abstract base interface for protocol-buffer-based RPC services. Services
130// themselves are abstract interfaces (implemented either by servers or as
131// stubs), but they subclass this base interface. The methods of this
132// interface can be used to call the methods of the Service without knowing
133// its exact type at compile time (analogous to Reflection).
134class PROTOBUF_EXPORT Service {
135 public:
136 inline Service() {}
137 virtual ~Service();
138
139 // When constructing a stub, you may pass STUB_OWNS_CHANNEL as the second
140 // parameter to the constructor to tell it to delete its RpcChannel when
141 // destroyed.
142 enum ChannelOwnership { STUB_OWNS_CHANNEL, STUB_DOESNT_OWN_CHANNEL };
143
144 // Get the ServiceDescriptor describing this service and its methods.
145 virtual const ServiceDescriptor* GetDescriptor() = 0;
146
147 // Call a method of the service specified by MethodDescriptor. This is
148 // normally implemented as a simple switch() that calls the standard
149 // definitions of the service's methods.
150 //
151 // Preconditions:
152 // * method->service() == GetDescriptor()
153 // * request and response are of the exact same classes as the objects
154 // returned by GetRequestPrototype(method) and
155 // GetResponsePrototype(method).
156 // * After the call has started, the request must not be modified and the
157 // response must not be accessed at all until "done" is called.
158 // * "controller" is of the correct type for the RPC implementation being
159 // used by this Service. For stubs, the "correct type" depends on the
160 // RpcChannel which the stub is using. Server-side Service
161 // implementations are expected to accept whatever type of RpcController
162 // the server-side RPC implementation uses.
163 //
164 // Postconditions:
165 // * "done" will be called when the method is complete. This may be
166 // before CallMethod() returns or it may be at some point in the future.
167 // * If the RPC succeeded, "response" contains the response returned by
168 // the server.
169 // * If the RPC failed, "response"'s contents are undefined. The
170 // RpcController can be queried to determine if an error occurred and
171 // possibly to get more information about the error.
172 virtual void CallMethod(const MethodDescriptor* method,
173 RpcController* controller, const Message* request,
174 Message* response, Closure* done) = 0;
175
176 // CallMethod() requires that the request and response passed in are of a
177 // particular subclass of Message. GetRequestPrototype() and
178 // GetResponsePrototype() get the default instances of these required types.
179 // You can then call Message::New() on these instances to construct mutable
180 // objects which you can then pass to CallMethod().
181 //
182 // Example:
183 // const MethodDescriptor* method =
184 // service->GetDescriptor()->FindMethodByName("Foo");
185 // Message* request = stub->GetRequestPrototype (method)->New();
186 // Message* response = stub->GetResponsePrototype(method)->New();
187 // request->ParseFromString(input);
188 // service->CallMethod(method, *request, response, callback);
189 virtual const Message& GetRequestPrototype(
190 const MethodDescriptor* method) const = 0;
191 virtual const Message& GetResponsePrototype(
192 const MethodDescriptor* method) const = 0;
193
194 private:
195 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Service);
196};
197
198// An RpcController mediates a single method call. The primary purpose of
199// the controller is to provide a way to manipulate settings specific to the
200// RPC implementation and to find out about RPC-level errors.
201//
202// The methods provided by the RpcController interface are intended to be a
203// "least common denominator" set of features which we expect all
204// implementations to support. Specific implementations may provide more
205// advanced features (e.g. deadline propagation).
206class PROTOBUF_EXPORT RpcController {
207 public:
208 inline RpcController() {}
209 virtual ~RpcController();
210
211 // Client-side methods ---------------------------------------------
212 // These calls may be made from the client side only. Their results
213 // are undefined on the server side (may crash).
214
215 // Resets the RpcController to its initial state so that it may be reused in
216 // a new call. Must not be called while an RPC is in progress.
217 virtual void Reset() = 0;
218
219 // After a call has finished, returns true if the call failed. The possible
220 // reasons for failure depend on the RPC implementation. Failed() must not
221 // be called before a call has finished. If Failed() returns true, the
222 // contents of the response message are undefined.
223 virtual bool Failed() const = 0;
224
225 // If Failed() is true, returns a human-readable description of the error.
226 virtual std::string ErrorText() const = 0;
227
228 // Advises the RPC system that the caller desires that the RPC call be
229 // canceled. The RPC system may cancel it immediately, may wait awhile and
230 // then cancel it, or may not even cancel the call at all. If the call is
231 // canceled, the "done" callback will still be called and the RpcController
232 // will indicate that the call failed at that time.
233 virtual void StartCancel() = 0;
234
235 // Server-side methods ---------------------------------------------
236 // These calls may be made from the server side only. Their results
237 // are undefined on the client side (may crash).
238
239 // Causes Failed() to return true on the client side. "reason" will be
240 // incorporated into the message returned by ErrorText(). If you find
241 // you need to return machine-readable information about failures, you
242 // should incorporate it into your response protocol buffer and should
243 // NOT call SetFailed().
244 virtual void SetFailed(const std::string& reason) = 0;
245
246 // If true, indicates that the client canceled the RPC, so the server may
247 // as well give up on replying to it. The server should still call the
248 // final "done" callback.
249 virtual bool IsCanceled() const = 0;
250
251 // Asks that the given callback be called when the RPC is canceled. The
252 // callback will always be called exactly once. If the RPC completes without
253 // being canceled, the callback will be called after completion. If the RPC
254 // has already been canceled when NotifyOnCancel() is called, the callback
255 // will be called immediately.
256 //
257 // NotifyOnCancel() must be called no more than once per request.
258 virtual void NotifyOnCancel(Closure* callback) = 0;
259
260 private:
261 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcController);
262};
263
264// Abstract interface for an RPC channel. An RpcChannel represents a
265// communication line to a Service which can be used to call that Service's
266// methods. The Service may be running on another machine. Normally, you
267// should not call an RpcChannel directly, but instead construct a stub Service
268// wrapping it. Example:
269// RpcChannel* channel = new MyRpcChannel("remotehost.example.com:1234");
270// MyService* service = new MyService::Stub(channel);
271// service->MyMethod(request, &response, callback);
272class PROTOBUF_EXPORT RpcChannel {
273 public:
274 inline RpcChannel() {}
275 virtual ~RpcChannel();
276
277 // Call the given method of the remote service. The signature of this
278 // procedure looks the same as Service::CallMethod(), but the requirements
279 // are less strict in one important way: the request and response objects
280 // need not be of any specific class as long as their descriptors are
281 // method->input_type() and method->output_type().
282 virtual void CallMethod(const MethodDescriptor* method,
283 RpcController* controller, const Message* request,
284 Message* response, Closure* done) = 0;
285
286 private:
287 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcChannel);
288};
289
290} // namespace protobuf
291} // namespace google
292
293#include <google/protobuf/port_undef.inc>
294
295#endif // GOOGLE_PROTOBUF_SERVICE_H__
296