libfsoresource: implement resource registration after registration was lost

In a few cases it can happen that the fsousage daemon dies. When it comes back again all
registrations are lost. Especially when using shadow resources this will let the usage
daemon wait for ever for the resource to register again. The AbstractDBusResource will
now watch if the usage bus disappears and then register the resource again when it comes
back.

In a stable system this case should never happen but when it happens it is better when the
system can solve this simple problem on its own.

1 files changed, 50 insertions, 7 deletions

diff --git a/libfsoresource/fsoresource/dbusresource.vala b/libfsoresource/fsoresource/dbusresource.vala
index f24dc18e..103c68cf 100644
--- a/libfsoresource/fsoresource/dbusresource.vala
+++ b/libfsoresource/fsoresource/dbusresource.vala
@@ -30,12 +30,45 @@ public abstract class AbstractDBusResource : FreeSmartphone.Resource, FsoFramewo
     private FreeSmartphone.Usage usage;
     private string name;
     private ObjectPath path;
+    private FsoFramework.DBusServiceNotifier dbusnotifier;
+    private bool resourceRegistrationPending = false;
+    private bool resourceRegistered = false;
+
+    private void onUsageServiceAppearing( string busname )
+    {
+        if (busname != FsoFramework.Usage.ServiceDBusName)
+            return;
+
+        if ( !resourceRegistered && !resourceRegistrationPending )
+        {
+            assert( logger.debug( @"$busname service appeared. Registering resource '$name' ..." ) );
+
+            resourceRegistrationPending = true;
+            Idle.add( () => { registerWithUsage(); return false; });
+        }
+    }
+
+    private void onUsageServiceDisappearing( string busname )
+    {
+        if (busname != FsoFramework.Usage.ServiceDBusName)
+            return;
+
+        resourceRegistered = false;
+    }
 
     public AbstractDBusResource( string name, FsoFramework.Subsystem subsystem )
     {
         this.name = name;
         this.subsystem = subsystem as FsoFramework.DBusSubsystem;
         this.path = new ObjectPath( "%s/%s".printf( FsoFramework.Resource.ServicePathPrefix, name ) );
+
+        this.dbusnotifier = new FsoFramework.DBusServiceNotifier();
+        this.dbusnotifier.notifyAppearing( FsoFramework.Usage.ServiceDBusName, onUsageServiceAppearing );
+        this.dbusnotifier.notifyDisappearing( FsoFramework.Usage.ServiceDBusName, onUsageServiceDisappearing );
+
+        resourceRegistrationPending = true;
+        resourceRegistered = false;
+
         Idle.add( () => {
             registerWithUsage();
             return false;
@@ -57,21 +90,31 @@ public abstract class AbstractDBusResource : FreeSmartphone.Resource, FsoFramewo
             conn.register_object<FreeSmartphone.Resource>( this.path, this );
             usage = yield conn.get_proxy<FreeSmartphone.Usage>( FsoFramework.Usage.ServiceDBusName, FsoFramework.Usage.ServicePathPrefix );
             yield usage.register_resource( name, path );
+
             logger.info( "Ok. Registered with org.freesmartphone.ousaged" );
-            return;
+
+            resourceRegistered = true;
         }
         catch ( Error e1 )
         {
             logger.error( @"Could not register $name with ousaged: $(e1.message); trying to enable the resource unconditionally" );
         }
-        try
-        {
-            yield enableResource();
-        }
-        catch ( Error e2 )
+
+#if 0
+        // FIXME why do we enable the resource here when fsouage does not told us to do so?
+        if ( resourceRegistered )
         {
-            logger.error( @"Can't enable the resource: $(e2.message)" );
+            try
+            {
+                yield enableResource();
+            }
+            catch ( Error e2 )
+            {
+                logger.error( @"Can't enable the resource: $(e2.message)" );
+            }
         }
+#endif
+        resourceRegistrationPending = false;
     }
 
     /**