Fix rpcclient's wait action in aync env. (#13307)

paddle/fluid/operators/distributed/CMakeLists.txt

@@ -20,6 +20,7 @@ if(WITH_GRPC)
     DEPS grpc++_unsecure grpc_unsecure gpr cares zlib protobuf sendrecvop_grpc scope profiler math_function SERIAL)
   cc_test(rpc_server_test SRCS rpc_server_test.cc
     DEPS sendrecvop_grpc grpc++_unsecure grpc_unsecure gpr cares zlib protobuf executor  proto_desc lookup_sparse_table_op SERIAL)
+  cc_test(varhandle_test SRCS varhandle_test.cc)
   return()
 endif()
 

paddle/fluid/operators/distributed/grpc_client.cc

@@ -59,40 +59,32 @@ GRPCClient::~GRPCClient() {
     }
     channels_.clear();
   }
-
   client_thread_->join();
 }
 
-bool GRPCClient::AsyncSendVar(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncSendVar(const std::string& ep,
                                       const platform::DeviceContext& ctx,
                                       const framework::Scope& scope,
-                              const std::string& var_name, int64_t time_out) {
+                                      const std::string& var_name,
+                                      int64_t time_out) {
   const platform::DeviceContext* p_ctx = &ctx;
   const std::string ep_val = ep;
   const std::string var_name_val = var_name;
   const framework::Scope* p_scope = &scope;
   const auto ch = GetChannel(ep_val);
+  SendProcessor* s = new SendProcessor(ch);
+  VarHandlePtr h(new VarHandle(ep, "Send", var_name_val, p_ctx, p_scope));
+  s->Prepare(h, time_out);
 
-  framework::AsyncIO([var_name_val, p_ctx, ep_val, p_scope, time_out, ch,
-                      this] {
+  framework::AsyncIO([var_name_val, p_scope, p_ctx, s, this] {
     auto* var = p_scope->FindVar(var_name_val);
 
     ::grpc::ByteBuffer req;
     SerializeToByteBuffer(var_name_val, var, *p_ctx, &req);
 
-    // varhandle
-    VarHandle var_h;
-    var_h.ep = ep_val;
-    var_h.scope = p_scope;
-    var_h.name = var_name_val;
-    var_h.ctx = p_ctx;
-    var_h.method = "Send";
-
-    VLOG(3) << var_h.String() << " begin";
+    VLOG(3) << s->GetVarHandlePtr()->String() << " begin";
 
     // stub context
-    SendProcessor* s = new SendProcessor(ch);
-    s->Prepare(var_h, time_out);
     s->response_call_back_ = nullptr;
 
     auto call = s->stub_g_.PrepareUnaryCall(
@@ -102,13 +94,13 @@ bool GRPCClient::AsyncSendVar(const std::string& ep,
   });
   req_count_++;
 
-  return true;
+  return h;
 }
 
 void ProcGetResponse(const VarHandle& var_h,
                      const ::grpc::ByteBuffer& ret_msg) {
   framework::Variable* outvar = nullptr;
-  DeserializeFromByteBuffer(ret_msg, *var_h.ctx, var_h.scope, &outvar);
+  DeserializeFromByteBuffer(ret_msg, *var_h.ctx(), var_h.scope(), &outvar);
 }
 
 template <typename T>
@@ -119,37 +111,30 @@ void RequestToByteBuffer(const T& proto, ::grpc::ByteBuffer* result) {
   result->Swap(&tmp);
 }
 
-bool GRPCClient::AsyncGetVar(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncGetVar(const std::string& ep,
                                      const platform::DeviceContext& ctx,
                                      const framework::Scope& scope,
-                             const std::string& var_name, int64_t time_out) {
+                                     const std::string& var_name,
+                                     int64_t time_out) {
   const platform::DeviceContext* p_ctx = &ctx;
   const std::string ep_val = ep;
   const std::string var_name_val = var_name;
   const framework::Scope* p_scope = &scope;
   const auto ch = GetChannel(ep_val);
+  GetProcessor* s = new GetProcessor(ch);
+  VarHandlePtr h(new VarHandle(ep, "Get", var_name_val, p_ctx, p_scope));
+  s->Prepare(h, time_out);
 
-  framework::AsyncIO([var_name_val, ep_val, p_scope, p_ctx, time_out, ch,
-                      this] {
+  framework::AsyncIO([var_name_val, p_scope, p_ctx, s, this] {
     // prepare input
     sendrecv::VariableMessage req;
     req.set_varname(var_name_val);
     ::grpc::ByteBuffer buf;
     RequestToByteBuffer<sendrecv::VariableMessage>(req, &buf);
 
-    // var handle
-    VarHandle var_h;
-    var_h.ep = ep_val;
-    var_h.scope = p_scope;
-    var_h.name = var_name_val;
-    var_h.ctx = p_ctx;
-    var_h.method = "Get";
-
-    VLOG(3) << var_h.String() << " begin";
+    VLOG(3) << s->GetVarHandlePtr()->String() << " begin";
 
     // stub context
-    GetProcessor* s = new GetProcessor(ch);
-    s->Prepare(var_h, time_out);
     s->response_call_back_ = ProcGetResponse;
 
     auto call = s->stub_g_.PrepareUnaryCall(
@@ -160,10 +145,10 @@ bool GRPCClient::AsyncGetVar(const std::string& ep,
 
   req_count_++;
 
-  return true;
+  return h;
 }
 
-bool GRPCClient::AsyncPrefetchVar(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncPrefetchVar(const std::string& ep,
                                           const platform::DeviceContext& ctx,
                                           const framework::Scope& scope,
                                           const std::string& in_var_name,
@@ -175,27 +160,21 @@ bool GRPCClient::AsyncPrefetchVar(const std::string& ep,
   const std::string out_var_name_val = out_var_name;
   const framework::Scope* p_scope = &scope;
   const auto ch = GetChannel(ep_val);
+  GetProcessor* s = new GetProcessor(ch);
+  VarHandlePtr h(
+      new VarHandle(ep, "Prefetch", out_var_name_val, p_ctx, p_scope));
+  s->Prepare(h, time_out);
 
   framework::AsyncIO([in_var_name_val, out_var_name_val, ep_val, p_scope, p_ctx,
-                      time_out, ch, this] {
+                      time_out, s, this] {
     auto* var = p_scope->FindVar(in_var_name_val);
 
     ::grpc::ByteBuffer req;
     SerializeToByteBuffer(in_var_name_val, var, *p_ctx, &req, out_var_name_val);
 
-    // var handle
-    VarHandle var_h;
-    var_h.ep = ep_val;
-    var_h.scope = p_scope;
-    var_h.name = out_var_name_val;
-    var_h.ctx = p_ctx;
-    var_h.method = "Prefetch";
-
-    VLOG(3) << var_h.String() << " begin";
+    VLOG(3) << s->GetVarHandlePtr()->String() << " begin";
 
     // stub context
-    GetProcessor* s = new GetProcessor(ch);
-    s->Prepare(var_h, time_out);
     s->response_call_back_ = ProcGetResponse;
 
     auto call = s->stub_g_.PrepareUnaryCall(
@@ -206,56 +185,68 @@ bool GRPCClient::AsyncPrefetchVar(const std::string& ep,
   });
 
   req_count_++;
-  return true;
+  return h;
 }
 
-void GRPCClient::AsyncSendBatchBarrier(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncSendBatchBarrier(const std::string& ep,
                                                int64_t time_out) {
   const auto ch = GetChannel(ep);
 
   BatchBarrierProcessor* s = new BatchBarrierProcessor(ch);
-  s->Prepare(time_out);
+  VarHandlePtr h(new VarHandle(ep, "BatchBarrier", BATCH_BARRIER_MESSAGE,
+                               nullptr, nullptr));
+  s->Prepare(h, time_out);
 
   sendrecv::VariableMessage req;
   req.set_varname(BATCH_BARRIER_MESSAGE);
   auto rpc = s->stub_->AsyncSendVariable(s->context_.get(), req, &cq_);
   rpc->Finish(&s->reply_, &s->status_, reinterpret_cast<void*>(s));
   req_count_++;
+  return h;
 }
 
-void GRPCClient::AsyncSendFetchBarrier(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncSendFetchBarrier(const std::string& ep,
                                                int64_t time_out) {
   const auto ch = GetChannel(ep);
   FetchBarrierProcessor* s = new FetchBarrierProcessor(ch);
-  s->Prepare(time_out);
+  VarHandlePtr h(new VarHandle(ep, "FetchBarrier", FETCH_BARRIER_MESSAGE,
+                               nullptr, nullptr));
+  s->Prepare(h, time_out);
 
   sendrecv::VariableMessage req;
   req.set_varname(FETCH_BARRIER_MESSAGE);
   auto rpc = s->stub_->AsyncGetVariable(s->context_.get(), req, &cq_);
   rpc->Finish(&s->reply_, &s->status_, reinterpret_cast<void*>(s));
   req_count_++;
+  return h;
 }
 
-void GRPCClient::AsyncSendComplete(const std::string& ep, int64_t time_out) {
+VarHandlePtr GRPCClient::AsyncSendComplete(const std::string& ep,
+                                           int64_t time_out) {
   const auto ch = GetChannel(ep);
 
   BatchBarrierProcessor* s = new BatchBarrierProcessor(ch);
-  s->Prepare(time_out);
+  VarHandlePtr h(
+      new VarHandle(ep, "SendComplete", COMPLETE_MESSAGE, nullptr, nullptr));
+  s->Prepare(h, time_out);
 
   sendrecv::VariableMessage req;
   req.set_varname(COMPLETE_MESSAGE);
   auto rpc = s->stub_->AsyncSendVariable(s->context_.get(), req, &cq_);
   rpc->Finish(&s->reply_, &s->status_, reinterpret_cast<void*>(s));
   req_count_++;
+  return h;
 }
 
-void GRPCClient::AsyncCheckpointNotify(const std::string& ep,
+VarHandlePtr GRPCClient::AsyncCheckpointNotify(const std::string& ep,
                                                const std::string& dir,
                                                int64_t time_out) {
   const auto ch = GetChannel(ep);
 
   CheckpointNotifyProcessor* s = new CheckpointNotifyProcessor(ch);
-  s->Prepare(time_out);
+  VarHandlePtr h(new VarHandle(ep, "CheckPointNotify", CHECKPOINT_SAVE_MESSAGE,
+                               nullptr, nullptr));
+  s->Prepare(h, time_out);
 
   sendrecv::VariableMessage req;
   req.set_varname(CHECKPOINT_SAVE_MESSAGE);
@@ -264,6 +255,7 @@ void GRPCClient::AsyncCheckpointNotify(const std::string& ep,
   auto rpc = s->stub_->AsyncCheckpointNotify(s->context_.get(), req, &cq_);
   rpc->Finish(&s->reply_, &s->status_, reinterpret_cast<void*>(s));
   req_count_++;
+  return h;
 }
 
 bool GRPCClient::Wait() {
@@ -276,25 +268,28 @@ void GRPCClient::Proceed() {
   void* tag = nullptr;
   bool ok = false;
 
+  VLOG(3) << "GRPCClient Proceed begin";
   while (!stopped_ && cq_.Next(&tag, &ok)) {
     BaseProcessor* c = static_cast<BaseProcessor*>(tag);
     GPR_ASSERT(ok);
     PADDLE_ENFORCE(c);
     if (c->status_.ok()) {
-      VLOG(3) << c->var_h_.String() << " process";
+      VLOG(3) << c->GetVarHandlePtr()->String() << " process";
       c->Process();
     } else if (c->status_.error_code() == grpc::StatusCode::DEADLINE_EXCEEDED) {
-      LOG(ERROR) << c->var_h_.String()
+      LOG(ERROR) << c->GetVarHandlePtr()->String()
                  << " meets grpc error:" << c->status_.error_message();
       {
         std::lock_guard<std::mutex> lk(sync_mutex_);
         ok_ = false;
       }
-      sync_cond_.notify_all();
+      c->Finish(false);
     } else {
-      LOG(FATAL) << c->var_h_.String()
+      LOG(FATAL) << c->GetVarHandlePtr()->String()
                  << " meets grpc error:" << c->status_.error_message();
+      c->Finish(false);
     }
+
     delete c;
     {
       std::lock_guard<std::mutex> lk(sync_mutex_);
@@ -302,6 +297,7 @@ void GRPCClient::Proceed() {
     }
     sync_cond_.notify_all();
   }
+  VLOG(3) << "GRPCClient Proceed end";
 }
 
 std::shared_ptr<grpc::Channel> GRPCClient::GetChannel(const std::string& ep) {

paddle/fluid/operators/distributed/grpc_client.h

@@ -53,15 +53,14 @@ void ProcGetResponse(const VarHandle& var_h, const grpc::ByteBuffer& msg);
 
 class BaseProcessor {
  public:
-  explicit BaseProcessor(std::shared_ptr<grpc::Channel> ch) {
-    context_ = nullptr;
-  }
+  BaseProcessor() { context_ = nullptr; }
 
   virtual ~BaseProcessor() {}
 
-  virtual void Prepare(const VarHandle& var_info, int64_t time_out) {
+  virtual void Prepare(VarHandlePtr h, int64_t time_out) {
+    var_h_ = h;
+
     context_.reset(new grpc::ClientContext());
-    var_h_ = var_info;
     context_->set_wait_for_ready(true);
     if (time_out) {
       std::chrono::system_clock::time_point deadline =
@@ -71,21 +70,21 @@ class BaseProcessor {
     }
   }
 
-  virtual void Prepare(int64_t time_out) {
-    context_.reset(new grpc::ClientContext());
-    context_->set_wait_for_ready(true);
-
-    std::chrono::system_clock::time_point deadline =
-        std::chrono::system_clock::now() + std::chrono::milliseconds(time_out);
-
-    context_->set_deadline(deadline);
+  void Process() {
+    ProcessImpl();
+    var_h_->Finish(true);
   }
 
-  virtual void Process() = 0;
+  VarHandlePtr GetVarHandlePtr() { return var_h_; }
+  bool Wait() { return var_h_->Wait(); }
+  void Finish(bool ok) { return var_h_->Finish(ok); }
+  virtual void ProcessImpl() = 0;
 
   std::unique_ptr<grpc::ClientContext> context_;
   grpc::Status status_;
-  VarHandle var_h_;
+
+ protected:
+  VarHandlePtr var_h_;
 };
 
 typedef std::function<void(const VarHandle&, const ::grpc::ByteBuffer&)>
@@ -94,13 +93,13 @@ typedef std::function<void(const VarHandle&, const ::grpc::ByteBuffer&)>
 class SendProcessor : public BaseProcessor {
  public:
   explicit SendProcessor(std::shared_ptr<grpc::Channel> ch)
-      : BaseProcessor(ch), stub_g_(ch) {}
+      : BaseProcessor(), stub_g_(ch) {}
 
   virtual ~SendProcessor() {}
 
-  virtual void Process() {
+  void ProcessImpl() override {
     if (response_call_back_) {
-      response_call_back_(var_h_, reply_);
+      response_call_back_(*var_h_.get(), reply_);
     }
   }
 
@@ -115,13 +114,13 @@ typedef std::function<void(const VarHandle&, const ::grpc::ByteBuffer&)>
 class GetProcessor : public BaseProcessor {
  public:
   explicit GetProcessor(std::shared_ptr<grpc::Channel> ch)
-      : BaseProcessor(ch), stub_g_(ch) {}
+      : BaseProcessor(), stub_g_(ch) {}
 
   virtual ~GetProcessor() {}
 
-  virtual void Process() {
+  void ProcessImpl() override {
     if (response_call_back_) {
-      response_call_back_(var_h_, reply_);
+      response_call_back_(*var_h_.get(), reply_);
     }
   }
 
@@ -133,13 +132,13 @@ class GetProcessor : public BaseProcessor {
 class BatchBarrierProcessor : public BaseProcessor {
  public:
   explicit BatchBarrierProcessor(std::shared_ptr<grpc::Channel> ch)
-      : BaseProcessor(ch) {
+      : BaseProcessor() {
     stub_ = sendrecv::SendRecvService::NewStub(ch);
   }
 
   virtual ~BatchBarrierProcessor() {}
 
-  virtual void Process() {}
+  void ProcessImpl() override {}
   sendrecv::VoidMessage reply_;
   std::unique_ptr<sendrecv::SendRecvService::Stub> stub_;
 };
@@ -147,13 +146,13 @@ class BatchBarrierProcessor : public BaseProcessor {
 class FetchBarrierProcessor : public BaseProcessor {
  public:
   explicit FetchBarrierProcessor(std::shared_ptr<grpc::Channel> ch)
-      : BaseProcessor(ch) {
+      : BaseProcessor() {
     stub_ = sendrecv::SendRecvService::NewStub(ch);
   }
 
   virtual ~FetchBarrierProcessor() {}
 
-  virtual void Process() {}
+  void ProcessImpl() override {}
   sendrecv::VariableMessage reply_;
   std::unique_ptr<sendrecv::SendRecvService::Stub> stub_;
 };
@@ -161,13 +160,13 @@ class FetchBarrierProcessor : public BaseProcessor {
 class CheckpointNotifyProcessor : public BaseProcessor {
  public:
   explicit CheckpointNotifyProcessor(std::shared_ptr<grpc::Channel> ch)
-      : BaseProcessor(ch) {
+      : BaseProcessor() {
     stub_ = sendrecv::SendRecvService::NewStub(ch);
   }
 
   virtual ~CheckpointNotifyProcessor() {}
 
-  virtual void Process() {}
+  void ProcessImpl() override {}
   sendrecv::VoidMessage reply_;
   std::unique_ptr<sendrecv::SendRecvService::Stub> stub_;
 };
@@ -177,32 +176,37 @@ class GRPCClient : public RPCClient {
   GRPCClient() : ok_(true), completed_(false), stopped_(false) {}
   virtual ~GRPCClient();
 
-  bool AsyncSendVar(const std::string& ep, const platform::DeviceContext& ctx,
-                    const framework::Scope& scope, const std::string& var_name,
+  VarHandlePtr AsyncSendVar(const std::string& ep,
+                            const platform::DeviceContext& ctx,
+                            const framework::Scope& scope,
+                            const std::string& var_name,
                             int64_t time_out = FLAGS_rpc_deadline) override;
 
-  bool AsyncGetVar(const std::string& ep, const platform::DeviceContext& ctx,
-                   const framework::Scope& scope, const std::string& var_name,
+  VarHandlePtr AsyncGetVar(const std::string& ep,
+                           const platform::DeviceContext& ctx,
+                           const framework::Scope& scope,
+                           const std::string& var_name,
                            int64_t time_out = FLAGS_rpc_deadline) override;
 
-  bool AsyncPrefetchVar(const std::string& ep,
+  VarHandlePtr AsyncPrefetchVar(const std::string& ep,
                                 const platform::DeviceContext& ctx,
                                 const framework::Scope& scope,
                                 const std::string& in_var_name,
                                 const std::string& out_var_name,
                                 int64_t time_out = FLAGS_rpc_deadline) override;
 
-  void AsyncSendBatchBarrier(const std::string& ep,
-                             int64_t time_out = FLAGS_rpc_deadline) override;
+  VarHandlePtr AsyncSendBatchBarrier(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) override;
 
-  void AsyncSendFetchBarrier(const std::string& ep,
-                             int64_t time_out = FLAGS_rpc_deadline) override;
+  VarHandlePtr AsyncSendFetchBarrier(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) override;
 
-  void AsyncCheckpointNotify(const std::string& ep, const std::string& dir,
+  VarHandlePtr AsyncCheckpointNotify(
+      const std::string& ep, const std::string& dir,
       int64_t time_out = FLAGS_rpc_deadline) override;
 
-  void AsyncSendComplete(const std::string& ep,
-                         int64_t time_out = FLAGS_rpc_deadline) override;
+  VarHandlePtr AsyncSendComplete(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) override;
 
   bool Wait() override;
 

paddle/fluid/operators/distributed/request_handler.h

@@ -28,6 +28,7 @@
 #include "paddle/fluid/framework/scope.h"
 #include "paddle/fluid/framework/selected_rows.h"
 #include "paddle/fluid/framework/var_type.h"
+#include "paddle/fluid/platform/macros.h"
 
 namespace paddle {
 namespace operators {
@@ -49,23 +50,77 @@ constexpr char kRequestPassBarrier[] = "RequestPassBarrier";
 
 class RPCServer;
 
-struct VarHandle {
-  // RPC endpoint.
-  std::string ep;
-  const platform::DeviceContext* ctx;
-  const framework::Scope* scope;
-  // Variable name.
-  std::string name;
-  // RPC method name.
-  std::string method;
+class VarHandle {
+ public:
+  VarHandle(const std::string ep, const std::string& method,
+            const std::string& name,
+            const platform::DeviceContext* p_ctx = nullptr,
+            const framework::Scope* p_scope = nullptr)
+      : ok_(kVarHandleDefaultState) {
+    ep_ = ep;
+    ctx_ = p_ctx;
+    scope_ = p_scope;
+    name_ = name;
+    method_ = method;
+  }
+
+  virtual ~VarHandle() {}
+
+ public:
+  bool Wait() {
+    {
+      std::unique_lock<std::mutex> lk(sync_mutex_);
+      wait_cond_.wait(lk, [this] { return ok_ != kVarHandleDefaultState; });
+    }
+    VLOG(7) << "VarHandle wait:" << ok_;
+    return ok_ != 0;
+  }
+
+  void Finish(bool ok) {
+    {
+      std::unique_lock<std::mutex> lk(sync_mutex_);
+      ok_ = ok;
+    }
+    VLOG(7) << "VarHandle finish:" << ok;
+    wait_cond_.notify_all();
+  }
 
   std::string String() const {
     std::ostringstream s;
-    s << method << " name:[" << name << "], ep:[" << ep << "]";
+    s << method_ << " name:[" << name_ << "], ep:[" << ep_ << "], ok:[" << ok_
+      << "]";
     return s.str();
   }
+
+  std::string ep() const { return ep_; }
+  const platform::DeviceContext* ctx() const { return ctx_; }
+  const framework::Scope* scope() const { return scope_; }
+  std::string name() const { return name_; }
+  std::string method() const { return method_; }
+
+ protected:
+  // RPC endpoint.
+  std::string ep_;
+  const platform::DeviceContext* ctx_;
+  const framework::Scope* scope_;
+  // Variable name.
+  std::string name_;
+  // RPC method name.
+  std::string method_;
+
+ protected:
+  std::mutex sync_mutex_;
+  std::condition_variable wait_cond_;
+  int ok_;
+
+  static const int kVarHandleDefaultState = -1;
+
+ private:
+  DISABLE_COPY_AND_ASSIGN(VarHandle);
 };
 
+typedef std::shared_ptr<VarHandle> VarHandlePtr;
+
 class RequestHandler {
  public:
   explicit RequestHandler(bool sync_mode)

paddle/fluid/operators/distributed/rpc_client.h

@@ -14,12 +14,14 @@
 
 #pragma once
 
+#include <condition_variable>  // NOLINT
 #include <string>
 #include "gflags/gflags.h"
 
 #include "paddle/fluid/framework/data_type.h"
 #include "paddle/fluid/framework/lod_tensor.h"
 #include "paddle/fluid/framework/scope.h"
+#include "paddle/fluid/operators/distributed/request_handler.h"
 
 DECLARE_int32(rpc_deadline);
 
@@ -31,37 +33,36 @@ class RPCClient {
  public:
   RPCClient() {}
   virtual ~RPCClient() {}
-  virtual bool AsyncSendVar(const std::string& ep,
+  virtual VarHandlePtr AsyncSendVar(const std::string& ep,
                                     const platform::DeviceContext& ctx,
                                     const framework::Scope& scope,
                                     const std::string& var_name,
                                     int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual bool AsyncGetVar(const std::string& ep,
+  virtual VarHandlePtr AsyncGetVar(const std::string& ep,
                                    const platform::DeviceContext& ctx,
                                    const framework::Scope& scope,
                                    const std::string& var_name,
                                    int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual bool AsyncPrefetchVar(const std::string& ep,
-                                const platform::DeviceContext& ctx,
-                                const framework::Scope& scope,
-                                const std::string& in_var_name,
+  virtual VarHandlePtr AsyncPrefetchVar(
+      const std::string& ep, const platform::DeviceContext& ctx,
+      const framework::Scope& scope, const std::string& in_var_name,
       const std::string& out_var_name,
       int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual void AsyncSendBatchBarrier(const std::string& ep,
-                                     int64_t time_out = FLAGS_rpc_deadline) = 0;
+  virtual VarHandlePtr AsyncSendBatchBarrier(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual void AsyncSendFetchBarrier(const std::string& ep,
-                                     int64_t time_out = FLAGS_rpc_deadline) = 0;
+  virtual VarHandlePtr AsyncSendFetchBarrier(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual void AsyncCheckpointNotify(const std::string& ep,
-                                     const std::string& dir,
+  virtual VarHandlePtr AsyncCheckpointNotify(
+      const std::string& ep, const std::string& dir,
       int64_t time_out = FLAGS_rpc_deadline) = 0;
 
-  virtual void AsyncSendComplete(const std::string& ep,
-                                 int64_t time_out = FLAGS_rpc_deadline) = 0;
+  virtual VarHandlePtr AsyncSendComplete(
+      const std::string& ep, int64_t time_out = FLAGS_rpc_deadline) = 0;
 
   // Complete tells all the pserver instances that finishe the training,
   // the pserver can reduce it's barrier count, and continue to train

paddle/fluid/operators/distributed/varhandle_test.cc

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include <unistd.h>
+#include <string>
+#include <thread>  // NOLINT
+
+#include "google/protobuf/text_format.h"
+#include "gtest/gtest.h"
+#include "paddle/fluid/operators/distributed/request_handler.h"
+
+using paddle::operators::distributed::VarHandlePtr;
+using paddle::operators::distributed::VarHandle;
+
+void WaitTrue(VarHandlePtr s) { EXPECT_TRUE(s->Wait()); }
+
+void WaitFalse(VarHandlePtr s) { EXPECT_FALSE(s->Wait()); }
+
+TEST(VarHandle, Run) {
+  std::vector<VarHandlePtr> a;
+  for (int i = 0; i < 12; i++) {
+    VarHandlePtr s(new VarHandle("", "", "", nullptr, nullptr));
+    a.push_back(s);
+  }
+
+  std::vector<std::unique_ptr<std::thread>> t;
+  for (int i = 0; i < 6; i++) {
+    t.emplace_back(new std::thread(WaitFalse, a[i]));
+  }
+
+  for (int i = 0; i < 6; i++) {
+    a[i]->Finish(false);
+    t[i]->join();
+  }
+
+  for (int i = 6; i < 12; i++) {
+    t.emplace_back(new std::thread(WaitTrue, a[i]));
+  }
+
+  for (int i = 6; i < 12; i++) {
+    a[i]->Finish(true);
+    t[i]->join();
+  }
+}

paddle/fluid/operators/prefetch_op.cc

@@ -44,16 +44,20 @@ class PrefetchOp : public framework::OperatorBase {
     distributed::RPCClient* rpc_client =
         distributed::RPCClient::GetInstance<RPCCLIENT_T>();
 
+    std::vector<distributed::VarHandlePtr> rets;
     for (size_t i = 0; i < ins.size(); i++) {
       if (NeedSend(scope, ins[i])) {
         VLOG(3) << "sending " << ins[i] << " to " << epmap[i] << " to get "
                 << outs[i] << " back";
-        rpc_client->AsyncPrefetchVar(epmap[i], ctx, scope, ins[i], outs[i]);
+        rets.push_back(rpc_client->AsyncPrefetchVar(epmap[i], ctx, scope,
+                                                    ins[i], outs[i]));
       } else {
         VLOG(3) << "don't send no-initialied variable: " << ins[i];
       }
     }
-    PADDLE_ENFORCE(rpc_client->Wait(), "internal error in RPCClient");
+    for (size_t i = 0; i < rets.size(); i++) {
+      PADDLE_ENFORCE(rets[i]->Wait(), "internal error in RPCClient");
+    }
   }
 };
 

paddle/fluid/operators/recv_op.cc

@@ -44,12 +44,15 @@ class RecvOp : public framework::OperatorBase {
     distributed::RPCClient* rpc_client =
         distributed::RPCClient::GetInstance<RPCCLIENT_T>();
 
+    std::vector<distributed::VarHandlePtr> rets;
     for (size_t i = 0; i < outs.size(); i++) {
       VLOG(3) << "getting " << outs[i] << " from " << epmap[i];
-      rpc_client->AsyncGetVar(epmap[i], ctx, scope, outs[i]);
+      rets.push_back(rpc_client->AsyncGetVar(epmap[i], ctx, scope, outs[i]));
     }
     if (sync_mode) {
-      PADDLE_ENFORCE(rpc_client->Wait(), "internal error in RPCClient");
+      for (size_t i = 0; i < rets.size(); i++) {
+        PADDLE_ENFORCE(rets[i]->Wait(), "internal error in RPCClient");
+      }
     }
   }
 };

paddle/fluid/operators/send_op.cc

@@ -15,6 +15,7 @@ limitations under the License. */
 #include <future>  // NOLINT
 #include <ostream>
 
+#include "paddle/fluid/framework/blocking_queue.h"
 #include "paddle/fluid/framework/data_type.h"
 #include "paddle/fluid/framework/lod_tensor.h"
 #include "paddle/fluid/framework/op_registry.h"
@@ -45,18 +46,19 @@ class SendOp : public framework::OperatorBase {
     distributed::RPCClient* rpc_client =
         distributed::RPCClient::GetInstance<RPCCLIENT_T>();
 
+    std::vector<distributed::VarHandlePtr> rets;
     for (size_t i = 0; i < ins.size(); i++) {
       if (NeedSend(scope, ins[i])) {
         VLOG(3) << "sending " << ins[i] << " to " << epmap[i];
-        // TODO(Yancey1989): we need to use an IO threadpool which has
-        // a larger number of threads than the computing threadpool.
-        rpc_client->AsyncSendVar(epmap[i], ctx, scope, ins[i]);
+        rets.push_back(rpc_client->AsyncSendVar(epmap[i], ctx, scope, ins[i]));
       } else {
         VLOG(3) << "don't send no-initialied variable: " << ins[i];
       }
     }
     if (sync_send) {
-      PADDLE_ENFORCE(rpc_client->Wait(), "internal error in RPCClient");
+      for (size_t i = 0; i < rets.size(); i++) {
+        PADDLE_ENFORCE(rets[i]->Wait(), "internal error in RPCClient");
+      }
     }
   }
 };