Use selectable event to terminate logger thread (#848)

settingThread of Logger select DB change with 1000ms timeout. It causes up to 1 second wait while destroy the logger instance. The 1 second wait is not necessary and can be replaced by SelectableEvent

common/logger.cpp

@@ -44,19 +44,21 @@ void Logger::terminateSettingThread()
 
     if (m_settingThread)
     {
-        m_runSettingThread = false;
+        m_stopEvent->notify();
 
         m_settingThread->join();
 
         m_settingThread = nullptr;
+
+        m_stopEvent = nullptr;
     }
 }
 
 void Logger::restartSettingThread()
 {
     terminateSettingThread();
 
-    m_runSettingThread = true;
+    m_stopEvent = std::make_unique<SelectableEvent>(0);
 
     m_settingThread.reset(new std::thread(&Logger::settingThread, this));
 }
@@ -195,8 +197,9 @@ void Logger::settingThread()
     auto table = std::make_shared<SubscriberStateTable>(&db, CFG_LOGGER_TABLE_NAME);
     selectables.emplace(CFG_LOGGER_TABLE_NAME, table);
     select.addSelectable(table.get());
+    select.addSelectable(m_stopEvent.get());
 
-    while (m_runSettingThread)
+    while (1)
     {
 
         Selectable *selectable = nullptr;
@@ -216,6 +219,11 @@ void Logger::settingThread()
             continue;
         }
 
+        if (selectable == m_stopEvent.get())
+        {
+            break;
+        }
+
         KeyOpFieldsValuesTuple koValues;
         SubscriberStateTable *subscriberStateTable = NULL;
         subscriberStateTable = dynamic_cast<SubscriberStateTable *>(selectable);

common/logger.h

@@ -10,6 +10,7 @@
 #include <functional>
 
 #include "concurrentmap.h"
+#include "selectableevent.h"
 
 namespace swss {
 
@@ -161,7 +162,7 @@ class Logger
     std::atomic<Output> m_output = { SWSS_SYSLOG };
     std::unique_ptr<std::thread> m_settingThread;
     std::mutex m_mutex;
-    volatile bool m_runSettingThread = true;
+    std::unique_ptr<SelectableEvent> m_stopEvent;
 };
 
 }