fix unlimited

src/ray/rpc/grpc_server.cc

@@ -107,10 +107,9 @@ void GrpcServer::Run() {
   // Create calls for all the server call factories.
   for (auto &entry : server_call_factories_) {
     for (int i = 0; i < num_threads_; i++) {
-      // Create a buffer of 100 calls for each RPC handler.
-      // TODO(edoakes): a small buffer should be fine and seems to have better
-      // performance, but we don't currently handle backpressure on the client.
-      int buffer_size = 100;
+      // When there is no max active RPC limit, a call will be added to the completetion
+      // queue before processing starts, so adding only 1 call is enough.
+      int buffer_size = 1;
       if (entry->GetMaxActiveRPCs() != -1) {
         buffer_size = entry->GetMaxActiveRPCs();
       }

src/ray/rpc/server_call.h

@@ -162,6 +162,12 @@ class ServerCallImpl : public ServerCall {
     start_time_ = absl::GetCurrentTimeNanos();
     ray::stats::STATS_grpc_server_req_handling.Record(1.0, call_name_);
     if (!io_service_.stopped()) {
+      if (factory_.GetMaxActiveRPCs() == -1) {
+        // Create a new `ServerCall` as completion queue tag before handling the request
+        // when no back pressure limit is set, so that new requests can continue to be
+        // pulled from the completion queue before this request is done.
+        factory_.CreateCall();
+      }
       io_service_.post([this] { HandleRequestImpl(); }, call_name_);
     } else {
       // Handle service for rpc call has stopped, we must handle the call here
@@ -173,16 +179,6 @@ class ServerCallImpl : public ServerCall {
 
   void HandleRequestImpl() {
     state_ = ServerCallState::PROCESSING;
-    // NOTE(hchen): This `factory` local variable is needed. Because `SendReply` runs in
-    // a different thread, and will cause `this` to be deleted.
-    const auto &factory = factory_;
-    if (factory.GetMaxActiveRPCs() == -1) {
-      // Create a new `ServerCall` to accept the next incoming request.
-      // We create this before handling the request only when no back pressure limit is
-      // set. So that the it can be populated by the completion queue in the background if
-      // a new request comes in.
-      factory.CreateCall();
-    }
     (service_handler_.*handle_request_function_)(
         request_,
         reply_,