added code from http://gist.github.com/389006

lib/delayed/backend/couch_mapper.rb

@@ -35,10 +35,15 @@ class Job < ::CouchRest::ExtendedDocument
         property :last_error
         timestamps!
 
-        view_by :priority, :run_at
         view_by :locked_by
+        view_by(:locked_at, :run_at,
+          :map => "function(doc){" +
+          " if(doc['couchrest-type'] == 'Job' && doc.run_at) {" +
+          " var locked_at = doc.locked_at || '';" +
+          " emit([locked_at, doc.run_at], null);}" +
+          " }")
 
-        save_callback :before, :set_default_run_at
+        set_callback :save, :before, :set_default_run_at
 
         def self.after_fork
           ::CouchRest.server = CouchRest.new('http://localhost:5984')
@@ -50,18 +55,21 @@ def self.db_time_now
         end
 
         def self.find_available(worker_name, limit = 5, max_run_time = Worker.max_run_time)
-
+          by_locked_at_and_run_at :start_key => [''], :end_key => ['', db_time_now], :limit => limit
         end
 
         # When a worker is exiting, make sure we don't have any locked jobs.
         def self.clear_locks!(worker_name)
-
+          docs = by_locked_by :startkey => [worker_name], :endkey => [worker_name, {}]
+          docs.each { |doc| doc.locked_by, doc.locked_at = nil, nil; }
+          database.bulk_save docs
         end
 
         # Lock this job for this worker.
         # Returns true if we have the lock, false otherwise.
         def lock_exclusively!(max_run_time, worker = worker_name)
-
+          locked_at, locked_by = self.class.db_time_now, worker
+          save
         end
 
         def self.delete_all