[sound-juicer] Retry query if MusicBrainz is busy

[Phillip Wood <pwood src gnome org>]

commit 9482097d44ebcbff4f928314b5f7ebe75a6d8b79
Author: Phillip Wood <phillip wood dunelm org uk>
Date:   Tue Apr 5 11:48:42 2016 +0100

    Retry query if MusicBrainz is busy
    
    Recently MusicBrainz has been returning error 503 for some queries when
    it is overloaded. This causes the lookup to fail. If it’s busy wait a
    while and retry the query. To avoid overloading MusicBrainz even more we
    limit the number of retries to 4 and wait 4 seconds for the first retry,
    a further 11 seconds for the second and then 30 seconds between
    subsequent retries.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764940
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764941

 libjuicer/sj-metadata-musicbrainz5.c |   50 ++++++++++++++++++++++-----------
 1 files changed, 33 insertions(+), 17 deletions(-)
---
diff --git a/libjuicer/sj-metadata-musicbrainz5.c b/libjuicer/sj-metadata-musicbrainz5.c
index 7245e8d..ed31b8f 100644
--- a/libjuicer/sj-metadata-musicbrainz5.c
+++ b/libjuicer/sj-metadata-musicbrainz5.c
@@ -198,24 +198,39 @@ query_musicbrainz (SjMetadataMusicbrainz5  *self,
 {
   Mb5Metadata metadata;
   char *inc[] = { "inc" };
+  gint64 delay = 4 * G_USEC_PER_SEC;
+  int count = 0;
   SjMetadataMusicbrainz5Private *priv = GET_PRIVATE (self);
   gint64 t;
 
-  if (g_cancellable_set_error_if_cancelled (cancellable, error))
-    return NULL;
+  while (TRUE) {
+    if (g_cancellable_set_error_if_cancelled (cancellable, error))
+      return NULL;
 
-  t = g_get_monotonic_time ();
-  while (t - last_query_time < G_USEC_PER_SEC) {
-    g_usleep (t - last_query_time + G_USEC_PER_SEC);
     t = g_get_monotonic_time ();
+    while (t - last_query_time < G_USEC_PER_SEC) {
+      g_usleep (t - last_query_time + G_USEC_PER_SEC);
+      t = g_get_monotonic_time ();
+    }
+
+    if (includes == NULL)
+      metadata = mb5_query_query (priv->mb, entity, id, "",
+                                  0, NULL, NULL);
+    else
+      metadata = mb5_query_query (priv->mb, entity, id, "",
+                                  1, inc, &includes);
+
+    if (metadata != NULL || ++count == 5 ||
+        mb5_query_get_lasthttpcode (priv->mb) != 503)
+      break;
+
+    g_usleep (delay);
+    if (delay < 30 * G_USEC_PER_SEC) {
+      delay *= 45; /* Increase delay by ~2√2 */
+      delay /= 16; /* Gives 4, 11, 30 */
+    }
   }
 
-  if (includes == NULL)
-    metadata = mb5_query_query (priv->mb, entity, id, "",
-                                0, NULL, NULL);
-  else
-    metadata = mb5_query_query (priv->mb, entity, id, "",
-                                1, inc, &includes);
   if (metadata == NULL)
     print_musicbrainz_query_error (self, entity, id);
 
@@ -963,6 +978,7 @@ mb5_list_albums (SjMetadata    *metadata,
   SjMetadataMusicbrainz5 *self;
   SjMetadataMusicbrainz5Private *priv;
   GList *albums = NULL;
+  Mb5Metadata disc_md;
   Mb5ReleaseList releases;
   Mb5Release release;
   const char *discid = NULL;
@@ -998,15 +1014,15 @@ mb5_list_albums (SjMetadata    *metadata,
   if (g_cancellable_set_error_if_cancelled (cancellable, error))
     goto free_url;
 
-  releases = mb5_query_lookup_discid(priv->mb, discid);
-
-  if (releases == NULL) {
-    print_musicbrainz_query_error (self, "discid", discid);
+  disc_md = query_musicbrainz (self, "discid", discid, NULL, cancellable, error);
+  if (disc_md == NULL) {
     if (url != NULL)
       *url = tmp_url;
     goto free_discid;
   }
 
+  releases = mb5_disc_get_releaselist (mb5_metadata_get_disc (disc_md));
+
   if (mb5_release_list_size (releases) == 0)
     return NULL;
 
@@ -1092,14 +1108,14 @@ artist-rels";
   }
   if (url != NULL)
     *url = tmp_url;
-  mb5_release_list_delete (releases);
+  mb5_metadata_delete (disc_md);
   discid_free (disc);
   return albums;
 
 
  free_releases:
   g_list_free_full (albums, (GDestroyNotify) album_details_free);
-  mb5_release_list_delete (releases);
+  mb5_metadata_delete (disc_md);
  free_url:
   g_free (tmp_url);
  free_discid: