Separate thread mutex, add test

src/Common/SystemLogBase.cpp

@@ -214,7 +214,7 @@ SystemLogBase<LogElement>::SystemLogBase(
 template <typename LogElement>
 void SystemLogBase<LogElement>::startup()
 {
-    std::lock_guard lock(queue->mutex);
+    std::lock_guard lock(thread_mutex);
     saving_thread = std::make_unique<ThreadFromGlobalPool>([this] { savingThreadFunction(); });
 }
 

src/Common/SystemLogBase.h

@@ -67,6 +67,7 @@ public:
     virtual void savingThreadFunction() = 0;
 
 protected:
+    std::mutex thread_mutex;
     std::unique_ptr<ThreadFromGlobalPool> saving_thread;
 
     bool is_shutdown = false;
@@ -93,10 +94,10 @@ public:
     Index pop(std::vector<LogElement>& output, bool& should_prepare_tables_anyway, bool& exit_this_thread);
     void confirm(Index to_flush_end);
 
+private:
     /// Data shared between callers of add()/flush()/shutdown(), and the saving thread
     std::mutex mutex;
 
-private:
     Poco::Logger * log;
 
     // Queue is bounded. But its size is quite large to not block in all normal cases.

src/Interpreters/SystemLog.cpp

@@ -358,7 +358,7 @@ template <typename LogElement>
 void SystemLog<LogElement>::stopFlushThread()
 {
     {
-        std::lock_guard lock(queue->mutex);
+        std::lock_guard lock(thread_mutex);
 
         if (!saving_thread || !saving_thread->joinable())
             return;

src/Interpreters/SystemLog.h

@@ -124,6 +124,7 @@ protected:
 
     using ISystemLog::is_shutdown;
     using ISystemLog::saving_thread;
+    using ISystemLog::thread_mutex;
     using Base::queue;
 
 private:

tests/queries/0_stateless/02813_starting_in_text_log.reference

@@ -0,0 +1 @@
+1

tests/queries/0_stateless/02813_starting_in_text_log.sql

@@ -0,0 +1,2 @@
+SYSTEM FLUSH LOGS;
+SELECT count() > 0 FROM system.text_log WHERE event_date >= yesterday() AND message LIKE '%Application: Starting ClickHouse%';