Add API route /health (#1079)

close #119

features/patroni_api.feature

@@ -8,6 +8,8 @@ Scenario: check API requests on a stand-alone server
 	Then I receive a response code 200
 	And I receive a response state running
 	And I receive a response role master
+	When I issue a GET request to http://127.0.0.1:8008/health
+	Then I receive a response code 200
 	When I issue a GET request to http://127.0.0.1:8008/replica
 	Then I receive a response code 503
 	When I run patronictl.py reinit batman postgres0 --force

patroni/api.py

@@ -102,6 +102,8 @@ class RestApiHandler(BaseHTTPRequestHandler):
             status_code = replica_status_code
         elif 'read-only' in path:
             status_code = 200 if primary_status_code == 200 else replica_status_code
+        elif 'health' in path:
+            status_code = 200 if response.get('state') == 'running' else 503
         elif cluster:  # dcs is available
             is_synchronous = cluster.is_synchronous_mode() and cluster.sync \
                     and cluster.sync.sync_standby == patroni.postgresql.name

tests/test_api.py

@@ -154,6 +154,8 @@ class TestRestApiHandler(unittest.TestCase):
             MockRestApiServer(RestApiHandler, 'GET /replica')
         with patch.object(RestApiHandler, 'get_postgresql_status', Mock(return_value={'role': 'master'})):
             MockRestApiServer(RestApiHandler, 'GET /replica')
+        with patch.object(RestApiHandler, 'get_postgresql_status', Mock(return_value={'state': 'running'})):
+            MockRestApiServer(RestApiHandler, 'GET /health')
         MockRestApiServer(RestApiHandler, 'GET /master')
         MockPatroni.dcs.cluster.sync.sync_standby = MockPostgresql.name
         MockPatroni.dcs.cluster.is_synchronous_mode = Mock(return_value=True)