[grpc-io] Re: multiple async clients for route_guide_callback_server example

[Dmitry Gorelov]

Oh man, it is not working even with *one *client! same problem in 
proto_utils.h


среда, 22 марта 2023 г. в 01:12:55 UTC+3, Dmitry Gorelov: 

> Hi All,
>
> please help to modify this peace of server code for bidirectional stream 
> in order to make it work correclty with *multiple clients* at one time. 
> Currently it crashes with segmentation fault in the proto_utils.h.
>
> class RouteGuideImpl final : public RouteGuide::CallbackService {
>  public:
>   explicit RouteGuideImpl(const std::string& db) {
>     routeguide::ParseDb(db, &feature_list_);
>   }  
>
>   grpc::ServerBidiReactor<RouteNote, RouteNote>* RouteChat(
>       CallbackServerContext* context) override {
>     class Chatter : public grpc::ServerBidiReactor<RouteNote, RouteNote> {
>      public:
>       Chatter(absl::Mutex* mu, std::vector<RouteNote>* received_notes)
>           : mu_(mu), received_notes_(received_notes) {
>         StartRead(&note_);
>       }
>
>       void OnDone() override { delete this; }
>       void OnReadDone(bool ok) override {
>         if (ok) {
>           // Unlike the other example in this directory that's not using
>           // the reactor pattern, we can't grab a local lock to secure the
>           // access to the notes vector, because the reactor will most 
> likely
>           // make us jump threads, so we'll have to use a different locking
>           // strategy. We'll grab the lock locally to build a copy of the
>           // list of nodes we're going to send, then we'll grab the lock
>           // again to append the received note to the existing vector.
>           mu_->Lock();
>           std::copy_if(received_notes_->begin(), received_notes_->end(),
>                        std::back_inserter(to_send_notes_),
>                        [this](const RouteNote& note) {
>                          return note.location().latitude() ==
>                                     note_.location().latitude() &&
>                                 note.location().longitude() ==
>                                     note_.location().longitude();
>                        });
>           mu_->Unlock();
>           notes_iterator_ = to_send_notes_.begin();
>           NextWrite();
>         } else {
>           std::cout << "some client finished" << std::endl;
>           Finish(Status::OK);
>         }
>       }
>       void OnWriteDone(bool /*ok*/) override { NextWrite(); }
>
>      private:
>       void NextWrite() {
>         if (notes_iterator_ != to_send_notes_.end()) {
>           StartWrite(&*notes_iterator_);
>           notes_iterator_++;
>         } else {
>           mu_->Lock();
>           received_notes_->push_back(note_);
>           mu_->Unlock();
>           StartRead(&note_);
>         }
>       }
>       RouteNote note_;
>       absl::Mutex* mu_;
>       std::vector<RouteNote>* received_notes_;
>       std::vector<RouteNote> to_send_notes_;
>       std::vector<RouteNote>::iterator notes_iterator_;
>     };
>     return new Chatter(&mu_, &received_notes_);
>   }
>
>  private:
>   std::vector<Feature> feature_list_;
>   absl::Mutex mu_;
>   std::vector<RouteNote> received_notes_ ABSL_GUARDED_BY(mu_);
> };
>

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