FIX: distributed cache failing to clear certain values sometimes

this makes the cache resilient to cross machine / forking concerns

lib/distributed_cache.rb

@@ -24,7 +24,7 @@ class DistributedCache
       begin
         current = @subscribers[i]
 
-        next if payload["origin"] == current.object_id
+        next if payload["origin"] == current.identity
         next if current.key != payload["hash_key"]
 
         hash = current.hash(message.site_id)
@@ -61,7 +61,7 @@ class DistributedCache
   end
 
   def self.publish(hash, message)
-    message[:origin] = hash.object_id
+    message[:origin] = hash.identity
     message[:hash_key] = hash.key
     DiscourseBus.publish(channel_name, message, { user_ids: [-1] })
   end
@@ -92,6 +92,11 @@ class DistributedCache
     @data = {}
   end
 
+  def identity
+    # fork resilient / multi machine identity
+    (@seed_id ||= SecureRandom.hex) + "#{Process.pid}"
+  end
+
   def []=(k,v)
     k = k.to_s if Symbol === k
     DistributedCache.set(self, k, v)