#2021 add HEAD support - minimal (#2360)

docs/rest_api.rst

@@ -7,7 +7,7 @@ Patroni has a rich REST API, which is used by Patroni itself during the leader r
 
 Health check endpoints
 ----------------------
-For all health check ``GET`` requests Patroni returns a JSON document with the status of the node, along with the HTTP status code. If you don't want or don't need the JSON document, you might consider using the ``OPTIONS`` method instead of ``GET``.
+For all health check ``GET`` requests Patroni returns a JSON document with the status of the node, along with the HTTP status code. If you don't want or don't need the JSON document, you might consider using the ``HEAD`` or ``OPTIONS`` method instead of ``GET``.
 
 - The following requests to Patroni REST API will return HTTP status code **200** only when the Patroni node is running as the primary with leader lock:
 

extras/confd/templates/haproxy.tmpl

@@ -18,14 +18,14 @@ listen stats
 
 listen master
 	bind *:5000
-	option httpchk OPTIONS /master
+	option httpchk HEAD /master
 	http-check expect status 200
 	default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
 {{range gets "/members/*"}}	server {{base .Key}} {{$data := json .Value}}{{base (replace (index (split $data.conn_url "/") 2) "@" "/" -1)}} maxconn 100 check port {{index (split (index (split $data.api_url "/") 2) ":") 1}}
 {{end}}
 listen replicas
 	bind *:5001
-	option httpchk OPTIONS /replica
+	option httpchk HEAD /replica
 	http-check expect status 200
 	default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
 {{range gets "/members/*"}}	server {{base .Key}} {{$data := json .Value}}{{base (replace (index (split $data.conn_url "/") 2) "@" "/" -1)}} maxconn 100 check port {{index (split (index (split $data.api_url "/") 2) ":") 1}}

patroni/api.py

@@ -38,6 +38,7 @@ class RestApiHandler(BaseHTTPRequestHandler):
         self.log_request(status_code)
 
     def _write_response(self, status_code, body, content_type='text/html', headers=None):
+        # TODO: try-catch ConnectionResetError: [Errno 104] Connection reset by peer and log it in DEBUG level
         self.send_response(status_code)
         headers = headers or {}
         if content_type:
@@ -185,6 +186,9 @@ class RestApiHandler(BaseHTTPRequestHandler):
     def do_OPTIONS(self):
         self.do_GET(write_status_code_only=True)
 
+    def do_HEAD(self):
+        self.do_GET(write_status_code_only=True)
+
     def do_GET_liveness(self):
         self._write_status_code_only(200)
 

tests/test_api.py

@@ -286,6 +286,9 @@ class TestRestApiHandler(unittest.TestCase):
     def test_do_OPTIONS(self):
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'OPTIONS / HTTP/1.0'))
 
+    def test_do_HEAD(self):
+        self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'HEAD / HTTP/1.0'))
+
     def test_do_GET_liveness(self):
         self.assertIsNotNone(MockRestApiServer(RestApiHandler, 'GET /liveness HTTP/1.0'))