loolwsd: notify clients of shutdown

Change-Id: I8dbe5752e8e36e2a1f6dee05f5f355f5a7b4d1b6
Reviewed-on: https://gerrit.libreoffice.org/31001
Reviewed-by: Ashod Nakashian <ashnakash@gmail.com>
Tested-by: Ashod Nakashian <ashnakash@gmail.com>

loolwsd/Admin.cpp

@@ -149,7 +149,7 @@ bool AdminRequestHandler::adminCommandHandler(const std::vector<char>& payload)
     else if (tokens[0] == "shutdown")
     {
         LOG_INF("Shutdown requested by admin.");
-        ShutdownFlag = true;
+        SigUtil::requestShutdown();
         return false;
     }
     else if (tokens[0] == "set" && tokens.count() > 1)

loolwsd/DocumentBroker.cpp

@@ -582,6 +582,7 @@ void DocumentBroker::alertAllUsers(const std::string& msg)
 {
     Util::assertIsLocked(_mutex);
 
+    LOG_DBG("Alerting all users: " << msg);
     for (auto& it : _sessions)
     {
         try

loolwsd/LOOLWSD.cpp

@@ -1971,7 +1971,7 @@ int LOOLWSD::main(const std::vector<std::string>& /*args*/)
     while (!TerminationFlag && !ShutdownFlag)
     {
         UnitWSD::get().invokeTest();
-        if (TerminationFlag)
+        if (TerminationFlag || SigUtil::handleShutdownRequest())
         {
             break;
         }
@@ -2078,7 +2078,6 @@ int LOOLWSD::main(const std::vector<std::string>& /*args*/)
     // and wait until sockets close.
     LOG_INF("Stopping server socket listening. ShutdownFlag: " <<
             ShutdownFlag << ", TerminationFlag: " << TerminationFlag);
-    Util::alertAllUsers("close: shutdown");
 
     srv.stop();
     srv2.stop();

loolwsd/common/SigUtil.cpp

@@ -54,6 +54,8 @@ std::atomic<bool> TerminationFlag(false);
 std::atomic<bool> ShutdownFlag(false);
 std::mutex SigHandlerTrap;
 
+static std::atomic<bool> ShutdownRequestFlag(false);
+
 namespace SigUtil
 {
     const char *signalName(const int signo)
@@ -125,7 +127,7 @@ namespace SigUtil
             Log::signalLog(" Shutdown signal received: ");
             Log::signalLog(signalName(signal));
             Log::signalLog("\n");
-            ShutdownFlag = true;
+            SigUtil::requestShutdown();
         }
         else
         {
@@ -242,6 +244,24 @@ namespace SigUtil
         strncpy(FatalGdbString, streamStr.c_str(), sizeof(FatalGdbString));
     }
 
+    void requestShutdown()
+    {
+        ShutdownRequestFlag = true;
+    }
+
+    bool handleShutdownRequest()
+    {
+        if (ShutdownRequestFlag)
+        {
+            LOG_INF("Shutdown requested. Initiating WSD shutdown.");
+            Util::alertAllUsers("close: shutdown");
+            ShutdownFlag = true;
+            return true;
+        }
+
+        return false;
+    }
+
     bool killChild(const int pid)
     {
         LOG_DBG("Killing PID: " << pid);

loolwsd/common/SigUtil.hpp

@@ -37,6 +37,21 @@ namespace SigUtil
     /// Trap all fatal signals to assist debugging.
     void setFatalSignals();
 
+    /// Requests the server to initiate graceful shutdown.
+    /// Shutting down is a multi-stage process, because
+    /// it can be requested via signals.
+    /// Since we need to notify clients, we can't
+    /// invoke the sockets while in a signal handler.
+    /// This flags the server to notify clients first
+    /// then flags for shutdown.
+    void requestShutdown();
+
+    /// Checks for shutdown request and,
+    /// after notifying clients, flags for
+    /// shutting down.
+    /// Returns true if shutdown is requested.
+    bool handleShutdownRequest();
+
     /// Kills a child process and returns true when
     /// child pid is removed from the process table
     /// after a certain (short) timeout.