From 80097f0752acb645c3be64e17410ada9e57db905 Mon Sep 17 00:00:00 2001
From: hzq <seuhezhiqiang@163.com>
Date: Wed, 6 Sep 2023 09:04:28 +0800
Subject: [PATCH] [fix](fragment mgr) Do not cancel queries when upgrading
 cluster. #23924

---
 be/src/runtime/fragment_mgr.cpp | 37 +++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/be/src/runtime/fragment_mgr.cpp b/be/src/runtime/fragment_mgr.cpp
index 4c8d4edf7e..8e347be172 100644
--- a/be/src/runtime/fragment_mgr.cpp
+++ b/be/src/runtime/fragment_mgr.cpp
@@ -991,22 +991,33 @@ void FragmentMgr::cancel_worker() {
             }
 
             const auto& running_fes = ExecEnv::GetInstance()->get_running_frontends();
-            for (const auto& q : _query_ctx_map) {
-                auto itr = running_fes.find(q.second->coord_addr);
-                if (itr != running_fes.end()) {
-                    // We use conservative strategy.
-                    // 1. If same process uuid, do not cancel
-                    // 2. If fe has zero process uuid, do not cancel
-                    // 3. If query's process uuid is zero, do not cancel
-                    if (q.second->get_fe_process_uuid() == itr->second.info.process_uuid ||
-                        itr->second.info.process_uuid == 0 ||
-                        q.second->get_fe_process_uuid() == 0) {
+
+            // We use a very conservative cancel strategy.
+            // 0. If there are no running frontends, do not cancel any queries.
+            // 1. If query's process uuid is zero, do not cancel
+            // 2. If same process uuid, do not cancel
+            // 3. If fe has zero process uuid, do not cancel
+            if (running_fes.empty()) {
+                LOG_EVERY_N(WARNING, 10)
+                        << "Could not find any running frontends, maybe we are upgrading? "
+                        << "We will not cancel any running queries in this situation.";
+            } else {
+                for (const auto& q : _query_ctx_map) {
+                    if (q.second->get_fe_process_uuid() == 0) {
                         continue;
                     }
-                }
 
-                // Coorninator of this query has already dead.
-                queries_to_cancel.push_back(q.first);
+                    auto itr = running_fes.find(q.second->coord_addr);
+                    if (itr != running_fes.end()) {
+                        if (q.second->get_fe_process_uuid() == itr->second.info.process_uuid ||
+                            itr->second.info.process_uuid == 0) {
+                            continue;
+                        }
+                    }
+
+                    // Coorninator of this query has already dead.
+                    queries_to_cancel.push_back(q.first);
+                }
             }
         }