add method available_services to ServiceRegistry, returns all services considered up for the supplied role

rethinkstuff/__init__.py

@@ -161,3 +161,11 @@ class ServiceRegistry(object):
         except r.ReqlNonExistenceError:
             return None
 
+    def available_services(self, role):
+        try:
+            result = self.r.table('services').filter({"role":role}).filter(
+                lambda svc: r.now().sub(svc["last_heartbeat"]) < 3 * svc["heartbeat_interval"]   #.default(20.0)
+            ).order_by("load").run()
+            return result
+        except r.ReqlNonExistenceError:
+            return []

tests/test_rethinker.py

@@ -151,3 +151,16 @@ def test_service_registry(r):
     assert svcreg.available_service("no-such-role") == None
     assert svcreg.available_service("yes-such-role") == None
 
+    svc0 = {
+        "role": "yes-such-role",
+        "load": 100.0,
+        "heartbeat_interval": 0.2,
+    }
+    svc1 = {
+        "role": "yes-such-role",
+        "load": 200.0,
+        "heartbeat_interval": 0.2,
+    }
+    svc0 = svcreg.heartbeat(svc0)
+    svc1 = svcreg.heartbeat(svc1)
+    assert len(svcreg.available_services("yes-such-role")) == 2