bgsave: add unit testing hooks for after bgsave fork & pre exit.

Signed-off-by: Michael Meeks <michael.meeks@collabora.com>
Change-Id: I35a2ec185762138dc85db39df3e7644c60acfddc

common/Unit.hpp

@@ -524,6 +524,10 @@ public:
     /// Post fork hook - just before we init the child kit
     virtual void postFork();
 
+    /// Called just after and before bg save process events
+    virtual void postBackgroundSaveFork() {}
+    virtual void preBackgroundSaveExit() {}
+
     /// Kit got a message
     virtual bool filterKitMessage(WebSocketHandler *, std::string &/* message */ )
     {

kit/Kit.cpp

@@ -1425,6 +1425,8 @@ bool Document::forkToSave(const std::function<void()> &childSave, int viewId)
         childSocket.reset();
         // now we just have a single socket to our parent
 
+        UnitKit::get().postBackgroundSaveFork();
+
         // Hard drop our previous connections to coolwsd and shared wakeups.x
         KitSocketPoll::cleanupChildProcess();
 

kit/KitWebSocket.cpp

@@ -209,6 +209,7 @@ void BgSaveChildWebSocketHandler::handleMessage(const std::vector<char>& data)
 void BgSaveChildWebSocketHandler::onDisconnect()
 {
     LOG_TRC("Disconnected background web socket to parent kit");
+    UnitKit::get().preBackgroundSaveExit();
     Util::forcedExit(EX_OK);
 }