From 4b3a2ce5a691ea4a3aa400d9ef157484b638982c Mon Sep 17 00:00:00 2001
From: shuke <37901441+shuke987@users.noreply.github.com>
Date: Tue, 14 Jun 2022 12:48:33 +0800
Subject: [PATCH] modify cached_gc_safe_point to atomic to prevent more request
 to PD (#5079)

ref pingcap/tiflash#4928
---
 dbms/src/Storages/Transaction/PDTiKVClient.cpp | 4 ++--
 dbms/src/Storages/Transaction/PDTiKVClient.h   | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/dbms/src/Storages/Transaction/PDTiKVClient.cpp b/dbms/src/Storages/Transaction/PDTiKVClient.cpp
index 5a4b751fd9c..a06f1a3ae64 100644
--- a/dbms/src/Storages/Transaction/PDTiKVClient.cpp
+++ b/dbms/src/Storages/Transaction/PDTiKVClient.cpp
@@ -22,7 +22,7 @@ namespace ErrorCodes
 extern const int LOGICAL_ERROR;
 }
 
-Timestamp PDClientHelper::cached_gc_safe_point = 0;
-std::chrono::time_point<std::chrono::system_clock> PDClientHelper::safe_point_last_update_time;
+std::atomic<Timestamp> PDClientHelper::cached_gc_safe_point = 0;
+std::atomic<std::chrono::time_point<std::chrono::system_clock>> PDClientHelper::safe_point_last_update_time;
 
 } // namespace DB
diff --git a/dbms/src/Storages/Transaction/PDTiKVClient.h b/dbms/src/Storages/Transaction/PDTiKVClient.h
index 4986c28f4ac..e5801cc7fae 100644
--- a/dbms/src/Storages/Transaction/PDTiKVClient.h
+++ b/dbms/src/Storages/Transaction/PDTiKVClient.h
@@ -29,6 +29,8 @@
 #include <Storages/Transaction/Types.h>
 #include <common/logger_useful.h>
 
+#include <atomic>
+
 // We define a shared ptr here, because TMTContext / SchemaSyncer / IndexReader all need to
 // `share` the resource of cluster.
 using KVClusterPtr = std::shared_ptr<pingcap::kv::Cluster>;
@@ -49,7 +51,7 @@ struct PDClientHelper
         {
             // In case we cost too much to update safe point from PD.
             std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
-            const auto duration = std::chrono::duration_cast<std::chrono::seconds>(now - safe_point_last_update_time);
+            const auto duration = std::chrono::duration_cast<std::chrono::seconds>(now - safe_point_last_update_time.load());
             const auto min_interval = std::max(Int64(1), safe_point_update_interval_seconds); // at least one second
             if (duration.count() < min_interval)
                 return cached_gc_safe_point;
@@ -73,8 +75,8 @@ struct PDClientHelper
     }
 
 private:
-    static Timestamp cached_gc_safe_point;
-    static std::chrono::time_point<std::chrono::system_clock> safe_point_last_update_time;
+    static std::atomic<Timestamp> cached_gc_safe_point;
+    static std::atomic<std::chrono::time_point<std::chrono::system_clock>> safe_point_last_update_time;
 };