From 9066b74f58ad7163dfc0ad8ef912cc50264997d1 Mon Sep 17 00:00:00 2001
From: WangXi <wangxi16@baidu.com>
Date: Mon, 15 Mar 2021 10:54:51 +0800
Subject: [PATCH] c_gen_nccl_id add SocketServer to persit server (#31589)

---
 .../operators/collective/c_gen_nccl_id_op.cc  |  3 ++-
 paddle/fluid/platform/gen_comm_id_helper.cc   | 18 +++++++++++++++++
 paddle/fluid/platform/gen_comm_id_helper.h    | 20 +++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/paddle/fluid/operators/collective/c_gen_nccl_id_op.cc b/paddle/fluid/operators/collective/c_gen_nccl_id_op.cc
index 485a6d7ec4..1592d809f9 100644
--- a/paddle/fluid/operators/collective/c_gen_nccl_id_op.cc
+++ b/paddle/fluid/operators/collective/c_gen_nccl_id_op.cc
@@ -75,7 +75,8 @@ class CGenNCCLIdOp : public framework::OperatorBase {
       platform::SendBroadCastCommID(endpoint_list, &nccl_ids);
     } else {
       std::string endpoint = Attr<std::string>("endpoint");
-      platform::RecvBroadCastCommID(endpoint, &nccl_ids);
+      int server_fd = platform::SocketServer::GetInstance(endpoint).socket();
+      platform::RecvBroadCastCommID(server_fd, endpoint, &nccl_ids);
     }
 
     CopyNCCLIDToVar(nccl_ids, func, scope);
diff --git a/paddle/fluid/platform/gen_comm_id_helper.cc b/paddle/fluid/platform/gen_comm_id_helper.cc
index ffe82371b1..f38603e80f 100644
--- a/paddle/fluid/platform/gen_comm_id_helper.cc
+++ b/paddle/fluid/platform/gen_comm_id_helper.cc
@@ -36,6 +36,8 @@ limitations under the License. */
 namespace paddle {
 namespace platform {
 
+std::once_flag SocketServer::init_flag_;
+
 constexpr char COMM_HEAD[] = "_pd_gen_comm_id_";
 
 // Check system calls, such as socket, bind.
@@ -330,6 +332,22 @@ void RecvBroadCastCommID(int server_fd, std::string endpoint,
   CloseSocket(client);
 }
 
+SocketServer& SocketServer::GetInstance(const std::string& end_point) {
+  static SocketServer instance;
+  std::call_once(init_flag_, [&]() {
+    instance.server_fd_ = CreateListenSocket(end_point);
+    instance.end_point_ = end_point;
+  });
+  PADDLE_ENFORCE_NE(instance.server_fd_, -1,
+                    platform::errors::Unavailable(
+                        "listen socket failed with end_point=%s", end_point));
+  PADDLE_ENFORCE_EQ(instance.end_point_, end_point,
+                    platform::errors::InvalidArgument(
+                        "old end_point=%s must equal with new end_point=%s",
+                        instance.end_point_, end_point));
+  return instance;
+}
+
 /// template instantiation
 #define INSTANT_TEMPLATE(Type)                                              \
   template void SendBroadCastCommID<Type>(std::vector<std::string> servers, \
diff --git a/paddle/fluid/platform/gen_comm_id_helper.h b/paddle/fluid/platform/gen_comm_id_helper.h
index 6014a2b4ff..c51c5ac6c8 100644
--- a/paddle/fluid/platform/gen_comm_id_helper.h
+++ b/paddle/fluid/platform/gen_comm_id_helper.h
@@ -17,6 +17,8 @@ limitations under the License. */
 #if defined(PADDLE_WITH_NCCL) || defined(PADDLE_WITH_RCCL) || \
     defined(PADDLE_WITH_XPU_BKCL)
 #include <functional>
+#include <memory>
+#include <mutex>
 #include <string>
 #include <vector>
 
@@ -39,6 +41,24 @@ void RecvBroadCastCommID(std::string endpoint,
 template <typename CommUniqueId>
 void RecvBroadCastCommID(int server_fd, std::string endpoint,
                          std::vector<CommUniqueId>* nccl_ids);
+
+class SocketServer {
+ public:
+  SocketServer() = default;
+
+  ~SocketServer() { CloseSocket(server_fd_); }
+
+  int socket() const { return server_fd_; }
+
+  static SocketServer& GetInstance(const std::string& end_point);
+
+ private:
+  int server_fd_{-1};
+  std::string end_point_;
+
+  static std::once_flag init_flag_;
+};
+
 }  // namespace platform
 }  // namespace paddle
 
-- 
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