Enable HAProxy HTTP Health Checks

Ceph radosgw supports [0] the swift health check endpoint
"/swift/healthcheck". This change adds the haproxy
configuration [1] necessary to take the response of "GET
/swift/healthcheck" into account when determining the health
of a radosgw service.

For testing, I verified that:
- HAProxy starts and responds to requests normally with this
  configuration.
- Servers with status != 2xx or 3xx are removed from the
  backend.
- Servers that take too long to respond are also removed
  from the backend. The default timeout value is 2s.

[0] https://tracker.ceph.com/issues/11682
[1] https://www.haproxy.com/documentation/hapee/2-0r1/onepage/#4.2-option%20httpchk

Closes-Bug: 1946280
Change-Id: I82634255ca3423fec3fc15c1e714dcb31db5da7a
(cherry picked from commit 31a4584169)

hooks/ceph_radosgw_context.py

@@ -22,6 +22,7 @@ from charmhelpers.contrib.openstack import context
 from charmhelpers.contrib.hahelpers.cluster import (
     determine_api_port,
     determine_apache_port,
+    https,
 )
 from charmhelpers.core.host import (
     cmp_pkgrevno,
@@ -68,12 +69,13 @@ class HAProxyContext(context.HAProxyContext):
     def __call__(self):
         ctxt = super(HAProxyContext, self).__call__()
         port = utils.listen_port()
+        service = 'cephradosgw-server'
 
         # Apache ports
         a_cephradosgw_api = determine_apache_port(port, singlenode_mode=True)
 
         port_mapping = {
-            'cephradosgw-server': [port, a_cephradosgw_api]
+            service: [port, a_cephradosgw_api]
         }
 
         ctxt['cephradosgw_bind_port'] = determine_api_port(
@@ -82,7 +84,16 @@ class HAProxyContext(context.HAProxyContext):
         )
 
         # for haproxy.conf
+        backend_options = {
+            service: [{
+                'option': 'httpchk GET /swift/healthcheck',
+            }]
+        }
+
         ctxt['service_ports'] = port_mapping
+        ctxt['backend_options'] = backend_options
+        ctxt['https'] = https()
+
         return ctxt
 
 

unit_tests/test_ceph_radosgw_context.py

@@ -63,7 +63,11 @@ class HAProxyContextTests(CharmTestCase):
         self.determine_api_port.return_value = 70
         expect = {
             'cephradosgw_bind_port': 70,
-            'service_ports': {'cephradosgw-server': [80, 70]}
+            'service_ports': {'cephradosgw-server': [80, 70]},
+            'backend_options': {'cephradosgw-server': [{
+                'option': 'httpchk GET /swift/healthcheck',
+            }]},
+            'https': False
         }
         self.assertEqual(expect, haproxy_context())