[clangd] Set gRPC deadlines to all remote index requests

[kbobyrev]

Summary

"TL;DR: Always set a deadline.", https://grpc.io/blog/deadlines/

[sammccall]

clang-tools-extra/clangd/index/remote/Client.cpp

63

I fear this may be too short - experience is going to be bad if it's really slow, but cutting off requests isn't going to be great.
I'd suggest bumping this up to at least a second... we should be sure we're logging timeouts too.

(If the connection is actually down, we shouldn't end up waiting for the deadline anyway in general: fail-fast is the default for grpc. https://github.com/grpc/grpc/blob/master/doc/wait-for-ready.md)

95

nit: I'd suggest generally avoiding const on non-pointer members, it messes with move semantics.

(In this case the object is always wrapped in unique_ptr before being exposed publicly, so it's actually fine. But have seen enough cases where it's initially fine and later not that I personally prefer to just always avoid it)

[kbobyrev]

Address review comments.

clang-tools-extra/clangd/index/remote/Client.cpp

 //===--- Client.cpp ----------------------------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include <grpc++/grpc++.h>
 
 #include "Client.h"
 #include "Index.grpc.pb.h"
 #include "index/Serialization.h"
 #include "marshalling/Marshalling.h"
 #include "support/Logger.h"
 #include "support/Trace.h"
 
+#include <chrono>
+
 namespace clang {
 namespace clangd {
 namespace remote {
 namespace {
 
 class IndexClient : public clangd::SymbolIndex {
   template <typename RequestT, typename ReplyT>
   using StreamingCall = std::unique_ptr<grpc::ClientReader<ReplyT>> (
       remote::SymbolIndex::Stub::*)(grpc::ClientContext *, const RequestT &);
 
-  // FIXME(kirillbobyrev): Set deadlines for requests.
   template <typename RequestT, typename ReplyT, typename ClangdRequestT,
             typename CallbackT>
   bool streamRPC(ClangdRequestT Request,
                  StreamingCall<RequestT, ReplyT> RPCCall,
                  CallbackT Callback) const {
     bool FinalResult = false;
     trace::Span Tracer(RequestT::descriptor()->name());
     const auto RPCRequest = toProtobuf(Request);
     grpc::ClientContext Context;
+    std::chrono::system_clock::time_point Deadline =
+        std::chrono::system_clock::now() + DeadlineWaitingTime;
+    Context.set_deadline(Deadline);
     auto Reader = (Stub.get()->*RPCCall)(&Context, RPCRequest);
     llvm::BumpPtrAllocator Arena;
     llvm::UniqueStringSaver Strings(Arena);
     ReplyT Reply;
     while (Reader->Read(&Reply)) {
       if (!Reply.has_stream_result()) {
         FinalResult = Reply.final_result();
         continue;
       }
       auto Sym = fromProtobuf(Reply.stream_result(), &Strings);
       if (!Sym)
         elog("Received invalid {0}", ReplyT::descriptor()->name());
       Callback(*Sym);
     }
     SPAN_ATTACH(Tracer, "status", Reader->Finish().ok());
     return FinalResult;
   }
 
 public:
-  IndexClient(std::shared_ptr<grpc::Channel> Channel)
-      : Stub(remote::SymbolIndex::NewStub(Channel)) {}
+  IndexClient(
+      std::shared_ptr<grpc::Channel> Channel,
+      std::chrono::milliseconds DeadlineTime = std::chrono::milliseconds(500))
+      : Stub(remote::SymbolIndex::NewStub(Channel)),
+        DeadlineWaitingTime(DeadlineTime) {}
 
   void lookup(const clangd::LookupRequest &Request,
               llvm::function_ref<void(const clangd::Symbol &)> Callback) const {
     streamRPC(Request, &remote::SymbolIndex::Stub::Lookup, Callback);
   }
 
   bool
   fuzzyFind(const clangd::FuzzyFindRequest &Request,
relations(const clangd::RelationsRequest &,
             llvm::function_ref<void(const SymbolID &, const clangd::Symbol &)>)
       const {}
 
   // IndexClient does not take any space since the data is stored on the server.
   size_t estimateMemoryUsage() const { return 0; }
 
 private:
   std::unique_ptr<remote::SymbolIndex::Stub> Stub;
+  // Each request will be terminated if it takes too long.
+  const std::chrono::milliseconds DeadlineWaitingTime;
 };
 
 } // namespace
 
 std::unique_ptr<clangd::SymbolIndex> getClient(llvm::StringRef Address) {
   const auto Channel =
       grpc::CreateChannel(Address.str(), grpc::InsecureChannelCredentials());
   Channel->GetState(true);
   return std::unique_ptr<clangd::SymbolIndex>(new IndexClient(Channel));
 }
 
 } // namespace remote
 } // namespace clangd
 } // namespace clang