diff --git a/cpp/src/scheduler/JobMgr.cpp b/cpp/src/scheduler/JobMgr.cpp
index 25a4932f03..bf22f7be2e 100644
--- a/cpp/src/scheduler/JobMgr.cpp
+++ b/cpp/src/scheduler/JobMgr.cpp
@@ -66,12 +66,10 @@ JobMgr::worker_function() {
         }
 
         auto tasks = build_task(job);
-        auto disk_list = res_mgr_->GetDiskResources();
-        if (!disk_list.empty()) {
-            if (auto disk = disk_list[0].lock()) {
-                for (auto& task : tasks) {
-                    disk->task_table().Put(task);
-                }
+        // disk resources NEVER be empty.
+        if (auto disk = res_mgr_->GetDiskResources()[0].lock()) {
+            for (auto& task : tasks) {
+                disk->task_table().Put(task);
             }
         }
     }
diff --git a/cpp/src/scheduler/ResourceMgr.cpp b/cpp/src/scheduler/ResourceMgr.cpp
index 3ea8a56ef8..d9da1f16bf 100644
--- a/cpp/src/scheduler/ResourceMgr.cpp
+++ b/cpp/src/scheduler/ResourceMgr.cpp
@@ -104,6 +104,10 @@ ResourceMgr::Connect(const std::string& name1, const std::string& name2, Connect
 void
 ResourceMgr::Clear() {
     std::lock_guard<std::mutex> lck(resources_mutex_);
+    if (running_) {
+        ENGINE_LOG_ERROR << "ResourceMgr is running, cannot clear.";
+        return;
+    }
     disk_resources_.clear();
     cpu_resources_.clear();
     gpu_resources_.clear();
diff --git a/cpp/src/scheduler/task/SearchTask.cpp b/cpp/src/scheduler/task/SearchTask.cpp
index 20962d8a10..ad8038a1f5 100644
--- a/cpp/src/scheduler/task/SearchTask.cpp
+++ b/cpp/src/scheduler/task/SearchTask.cpp
@@ -34,6 +34,7 @@ static constexpr size_t PARALLEL_REDUCE_BATCH = 1000;
 
 std::mutex XSearchTask::merge_mutex_;
 
+// TODO(wxyu): remove unused code
 // bool
 // NeedParallelReduce(uint64_t nq, uint64_t topk) {
 //    server::ServerConfig &config = server::ServerConfig::GetInstance();