Bug 685986 - ESourceRegistry: Wait for signals after creating sources

e_source_registry_create_sources_sync() now waits for "object-added"
signals from its GDBusObjectManagerClient before returning.  This allows
the newly-created ESources to be obtained immediately after the function
returns.  Prior to this there was a small delay before the newly-created
ESources became available through the ESourceRegistry API.

There is a caveat to this.  If any of the scratch ESources reference a
parent UID which is not presently exported by the registry service, the
registry service will refuse to export the newly-created ESource until
its parent becomes available.

In this scenario, to avoid waiting forever for an "object-added" signal
that isn't coming, we place a limit on the wait time (two seconds).  If
this time limit expires, we return from the function regardless.

diff --git a/libedataserver/e-source-registry.c b/libedataserver/e-source-registry.c
index 5664135..32feabb 100644 (file)
--- a/libedataserver/e-source-registry.c
+++ b/libedataserver/e-source-registry.c
@@ -95,6 +95,7 @@
 
 typedef struct _AsyncContext AsyncContext;
 typedef struct _AuthContext AuthContext;
+typedef struct _CreateContext CreateContext;
 typedef struct _SourceClosure SourceClosure;
 typedef struct _ThreadClosure ThreadClosure;
 
@@ -135,6 +136,13 @@ struct _AuthContext {
        GError **error;
 };
 
+/* Used in e_source_registry_create_sources_sync() */
+struct _CreateContext {
+       GHashTable *pending_uids;
+       GMainContext *main_context;
+       GMainLoop *main_loop;
+};
+
 struct _SourceClosure {
        ESourceRegistry *registry;
        ESource *source;
@@ -223,6 +231,37 @@ auth_context_free (AuthContext *auth_context)
        g_slice_free (AuthContext, auth_context);
 }
 
+static CreateContext *
+create_context_new (void)
+{
+       CreateContext *create_context;
+
+       create_context = g_slice_new0 (CreateContext);
+
+       create_context->pending_uids = g_hash_table_new_full (
+               (GHashFunc) g_str_hash,
+               (GEqualFunc) g_str_equal,
+               (GDestroyNotify) g_free,
+               (GDestroyNotify) NULL);
+
+       create_context->main_context = g_main_context_new ();
+
+       create_context->main_loop = g_main_loop_new (
+               create_context->main_context, FALSE);
+
+       return create_context;
+}
+
+static void
+create_context_free (CreateContext *create_context)
+{
+       g_main_loop_unref (create_context->main_loop);
+       g_main_context_unref (create_context->main_context);
+       g_hash_table_unref (create_context->pending_uids);
+
+       g_slice_free (CreateContext, create_context);
+}
+
 static void
 source_closure_free (SourceClosure *closure)
 {
@@ -569,6 +608,9 @@ source_registry_add_source (ESourceRegistry *registry,
 {
        const gchar *uid;
 
+       /* This is called in the manager thread during initialization
+        * and in response to "object-added" signals from the manager. */
+
        uid = e_source_get_uid (source);
        g_return_if_fail (uid != NULL);
 
@@ -593,28 +635,16 @@ source_registry_add_source (ESourceRegistry *registry,
        g_mutex_unlock (registry->priv->sources_lock);
 
        source_registry_sources_insert (registry, source);
-
-       g_signal_emit (registry, signals[SOURCE_ADDED], 0, source);
-}
-
-static void
-source_registry_remove_source (ESourceRegistry *registry,
-                               ESource *source)
-{
-       g_object_ref (source);
-
-       if (source_registry_sources_remove (registry, source))
-               g_signal_emit (registry, signals[SOURCE_REMOVED], 0, source);
-
-       g_object_unref (source);
 }
 
 static gboolean
 source_registry_object_added_idle_cb (gpointer user_data)
 {
        SourceClosure *closure = user_data;
+       ESourceRegistry *registry = closure->registry;
+       ESource *source = closure->source;
 
-       source_registry_add_source (closure->registry, closure->source);
+       g_signal_emit (registry, signals[SOURCE_ADDED], 0, source);
 
        return FALSE;
 }
@@ -633,6 +663,10 @@ source_registry_object_added_cb (GDBusObjectManager *object_manager,
        source = source_registry_new_source (registry, dbus_object);
        g_return_if_fail (source != NULL);
 
+       /* Add the new ESource to our internal hash table so it can be
+        * obtained through e_source_registry_ref_source() immediately. */
+       source_registry_add_source (registry, source);
+
        /* Schedule a callback on the ESourceRegistry's GMainContext. */
 
        closure = g_slice_new0 (SourceClosure);
@@ -654,8 +688,13 @@ static gboolean
 source_registry_object_removed_idle_cb (gpointer user_data)
 {
        SourceClosure *closure = user_data;
+       ESourceRegistry *registry = closure->registry;
+       ESource *source = closure->source;
 
-       source_registry_remove_source (closure->registry, closure->source);
+       /* Removing the ESource won't finalize it because the
+        * SourceClosure itself still holds a reference on it. */
+       if (source_registry_sources_remove (registry, source))
+               g_signal_emit (registry, signals[SOURCE_REMOVED], 0, source);
 
        return FALSE;
 }
@@ -2002,6 +2041,49 @@ source_registry_create_sources_thread (GSimpleAsyncResult *simple,
                g_simple_async_result_take_error (simple, error);
 }
 
+/* Helper for e_source_registry_create_sources_sync() */
+static gboolean
+source_registry_create_sources_main_loop_quit_cb (gpointer user_data)
+{
+       GMainLoop *main_loop = user_data;
+
+       g_main_loop_quit (main_loop);
+
+       return FALSE;
+}
+
+/* Helper for e_source_registry_create_sources_sync() */
+static void
+source_registry_create_sources_object_added_cb (GDBusObjectManager *object_manager,
+                                                GDBusObject *dbus_object,
+                                                CreateContext *create_context)
+{
+       EDBusObject *e_dbus_object;
+       EDBusSource *e_dbus_source;
+       const gchar *uid;
+
+       e_dbus_object = E_DBUS_OBJECT (dbus_object);
+       e_dbus_source = e_dbus_object_get_source (e_dbus_object);
+       uid = e_dbus_source_get_uid (e_dbus_source);
+
+       g_hash_table_remove (create_context->pending_uids, uid);
+
+       /* The hash table will be empty when all of the expected
+        * GDBusObjects have been added to the GDBusObjectManager. */
+       if (g_hash_table_size (create_context->pending_uids) == 0) {
+               GSource *idle_source;
+
+               idle_source = g_idle_source_new ();
+               g_source_set_callback (
+                       idle_source,
+                       source_registry_create_sources_main_loop_quit_cb,
+                       g_main_loop_ref (create_context->main_loop),
+                       (GDestroyNotify) g_main_loop_unref);
+               g_source_attach (idle_source, create_context->main_context);
+               g_source_unref (idle_source);
+       }
+}
+
 /**
  * e_source_registry_create_sources_sync:
  * @registry: an #ESourceRegistry
@@ -2026,9 +2108,11 @@ e_source_registry_create_sources_sync (ESourceRegistry *registry,
                                        GCancellable *cancellable,
                                        GError **error)
 {
+       CreateContext *create_context;
        GVariantBuilder builder;
        GVariant *variant;
        GList *link;
+       gulong object_added_id;
        gboolean success;
 
        g_return_val_if_fail (E_IS_SOURCE_REGISTRY (registry), FALSE);
@@ -2037,15 +2121,21 @@ e_source_registry_create_sources_sync (ESourceRegistry *registry,
        for (link = list_of_sources; link != NULL; link = g_list_next (link))
                g_return_val_if_fail (E_IS_SOURCE (link->data), FALSE);
 
+       create_context = create_context_new ();
+       g_main_context_push_thread_default (create_context->main_context);
+
        g_variant_builder_init (&builder, G_VARIANT_TYPE_ARRAY);
 
        for (link = list_of_sources; link != NULL; link = g_list_next (link)) {
                ESource *source;
-               const gchar *uid;
                gchar *source_data;
+               gchar *uid;
 
                source = E_SOURCE (link->data);
-               uid = e_source_get_uid (source);
+               uid = e_source_dup_uid (source);
+
+               /* Takes ownership of the UID string. */
+               g_hash_table_add (create_context->pending_uids, uid);
 
                source_data = e_source_to_string (source, NULL);
                g_variant_builder_add (&builder, "{ss}", uid, source_data);
@@ -2054,6 +2144,14 @@ e_source_registry_create_sources_sync (ESourceRegistry *registry,
 
        variant = g_variant_builder_end (&builder);
 
+       /* Use G_CONNECT_AFTER so source_registry_object_added_cb()
+        * runs first and actually adds the ESource to the internal
+        * hash table before we go quitting our main loop. */
+       object_added_id = g_signal_connect_after (
+               registry->priv->dbus_object_manager, "object-added",
+               G_CALLBACK (source_registry_create_sources_object_added_cb),
+               create_context);
+
        /* This function sinks the floating GVariant reference. */
        success = e_dbus_source_manager_call_create_sources_sync (
                registry->priv->dbus_source_manager,
@@ -2061,6 +2159,31 @@ e_source_registry_create_sources_sync (ESourceRegistry *registry,
 
        g_variant_builder_clear (&builder);
 
+       /* Wait for an "object-added" signal for each created ESource.
+        * But also set a short timeout to avoid getting stuck here in
+        * case the registry service adds sources to its orphan table,
+        * which prevents them from being exported over D-Bus. */
+       if (success) {
+               GSource *timeout_source;
+
+               timeout_source = g_timeout_source_new_seconds (2);
+               g_source_set_callback (
+                       timeout_source,
+                       source_registry_create_sources_main_loop_quit_cb,
+                       g_main_loop_ref (create_context->main_loop),
+                       (GDestroyNotify) g_main_loop_unref);
+               g_source_attach (timeout_source, create_context->main_context);
+               g_source_unref (timeout_source);
+
+               g_main_loop_run (create_context->main_loop);
+       }
+
+       g_signal_handler_disconnect (
+               registry->priv->dbus_object_manager, object_added_id);
+
+       g_main_context_pop_thread_default (create_context->main_context);
+       create_context_free (create_context);
+
        return success;
 }