OStatus/FeedSub: tweaked PuSH feed garbage collection so other plugins can declare usage of a low-level feed or an OStatus profile besides profile subscriptions & group memberships.

SubMirror: redid add-mirror frontend to accept a feed URL, then pass that on to OStatus, instead of pulling from your subscriptions.
Profile: tweaked subscriberCount() so it doesn't subtract 1 for foreign profiles who aren't subscribed to themselves; instead excludes the self-subscription in the count query.
Memcached_DataObject: tweak to avoid extra error spew in the DB error raising

Work in progress: tweaking feedsub garbage collection so we can count other uses

3 files changed, 74 insertions, 19 deletions

diff --git a/plugins/OStatus/OStatusPlugin.php b/plugins/OStatus/OStatusPlugin.php
index 70971c5b3..3b073a5d1 100644
--- a/plugins/OStatus/OStatusPlugin.php
+++ b/plugins/OStatus/OStatusPlugin.php
@@ -480,6 +480,24 @@ class OStatusPlugin extends Plugin
     }
 
     /**
+     * Tell the FeedSub infrastructure whether we have any active OStatus
+     * usage for the feed; if not it'll be able to garbage-collect the
+     * feed subscription.
+     * 
+     * @param FeedSub $feedsub
+     * @param integer $count in/out
+     * @return mixed hook return code
+     */
+    function onFeedSubSubscriberCount($feedsub, &$count)
+    {
+        $oprofile = Ostatus_profile::staticGet('feeduri', $feedsub->uri);
+        if ($oprofile) {
+            $count += $oprofile->subscriberCount();
+        }
+        return true;
+    }
+
+    /**
      * When about to subscribe to a remote user, start a server-to-server
      * PuSH subscription if needed. If we can't establish that, abort.
      *
diff --git a/plugins/OStatus/classes/FeedSub.php b/plugins/OStatus/classes/FeedSub.php
index b10509dae..9cd35e29c 100644
--- a/plugins/OStatus/classes/FeedSub.php
+++ b/plugins/OStatus/classes/FeedSub.php
@@ -255,6 +255,9 @@ class FeedSub extends Memcached_DataObject
     /**
      * Send a PuSH unsubscription request to the hub for this feed.
      * The hub will later send us a confirmation POST to /main/push/callback.
+     * Warning: this will cancel the subscription even if someone else in
+     * the system is using it. Most callers will want garbageCollect() instead,
+     * which confirms there's no uses left.
      *
      * @return bool true on success, false on failure
      * @throws ServerException if feed state is not valid
@@ -275,6 +278,33 @@ class FeedSub extends Memcached_DataObject
         return $this->doSubscribe('unsubscribe');
     }
 
+    /**
+     * Check if there are any active local uses of this feed, and if not then
+     * make sure it's inactive, unsubscribing if necessary.
+     *
+     * @return boolean true if the subscription is now inactive, false if still active.
+     */
+    public function garbageCollect()
+    {
+        if ($this->sub_state == '' || $this->sub_state == 'inactive') {
+            // No active PuSH subscription, we can just leave it be.
+            return true;
+        } else {
+            // PuSH subscription is either active or in an indeterminate state.
+            // Check if we're out of subscribers, and if so send an unsubscribe.
+            $count = 0;
+            Event::handle('FeedSubSubscriberCount', array($this, &$count));
+
+            if ($count) {
+                common_log(LOG_INFO, __METHOD__ . ': ok, ' . $count . ' user(s) left for ' . $this->uri);
+                return false;
+            } else {
+                common_log(LOG_INFO, __METHOD__ . ': unsubscribing, no users left for ' . $this->uri);
+                return $this->unsubscribe();
+            }
+        }
+    }
+
     protected function doSubscribe($mode)
     {
         $orig = clone($this);
diff --git a/plugins/OStatus/classes/Ostatus_profile.php b/plugins/OStatus/classes/Ostatus_profile.php
index 5d3f37cd0..2d7c632e6 100644
--- a/plugins/OStatus/classes/Ostatus_profile.php
+++ b/plugins/OStatus/classes/Ostatus_profile.php
@@ -215,22 +215,13 @@ class Ostatus_profile extends Memcached_DataObject
     }
 
     /**
-     * Send a PuSH unsubscription request to the hub for this feed.
-     * The hub will later send us a confirmation POST to /main/push/callback.
+     * Check if this remote profile has any active local subscriptions, and
+     * if not drop the PuSH subscription feed.
      *
      * @return bool true on success, false on failure
-     * @throws ServerException if feed state is not valid
      */
     public function unsubscribe() {
-        $feedsub = FeedSub::staticGet('uri', $this->feeduri);
-        if (!$feedsub || $feedsub->sub_state == '' || $feedsub->sub_state == 'inactive') {
-            // No active PuSH subscription, we can just leave it be.
-            return true;
-        } else {
-            // PuSH subscription is either active or in an indeterminate state.
-            // Send an unsubscribe.
-            return $feedsub->unsubscribe();
-        }
+        $this->garbageCollect();
     }
 
     /**
@@ -241,19 +232,35 @@ class Ostatus_profile extends Memcached_DataObject
      */
     public function garbageCollect()
     {
+        $feedsub = FeedSub::staticGet('uri', $this->feeduri);
+        return $feedsub->garbageCollect();
+    }
+
+    /**
+     * Check if this remote profile has any active local subscriptions, so the
+     * PuSH subscription layer can decide if it can drop the feed.
+     *
+     * This gets called via the FeedSubSubscriberCount event when running
+     * FeedSub::garbageCollect().
+     *
+     * @return int
+     */
+    public function subscriberCount()
+    {
         if ($this->isGroup()) {
             $members = $this->localGroup()->getMembers(0, 1);
             $count = $members->N;
         } else {
             $count = $this->localProfile()->subscriberCount();
         }
-        if ($count == 0) {
-            common_log(LOG_INFO, "Unsubscribing from now-unused remote feed $this->feeduri");
-            $this->unsubscribe();
-            return true;
-        } else {
-            return false;
-        }
+        common_log(LOG_INFO, __METHOD__ . " SUB COUNT BEFORE: $count");
+
+        // Other plugins may be piggybacking on OStatus without having
+        // an active group or user-to-user subscription we know about.
+        Event::handle('Ostatus_profileSubscriberCount', array($this, &$count));
+        common_log(LOG_INFO, __METHOD__ . " SUB COUNT AFTER: $count");
+
+        return $count;
     }
 
     /**