Add keepalive support for auth requests (#8219)

* Add keepalive support for auth requests

* Fix typo

* Address PR comments

* Log warning when auth-url contains variable in its host:port
* Generate upstream name without replacing dots to underscores in server name
* Add comment in the nginx template when the keepalive upstream block is referenced

* Workaround for auth_request module ignores keepalive in upstream block

* The `auth_request` module does not support HTTP keepalives in upstream block:
  https://trac.nginx.org/nginx/ticket/1579
* As a workaround we use ngx.location.capture but unfortunately it does not
  support HTTP/2 so `use-http2` configuration parameter is needed.

* Handle PR comments

* Address PR comments

* Handle invalid values for int parameters

* Handle PR comments

* Fix e2e test

internal/ingress/annotations/authreq/main_test.go

@@ -243,6 +243,71 @@ func TestCacheDurationAnnotations(t *testing.T) {
 	}
 }
 
+func TestKeepaliveAnnotations(t *testing.T) {
+	ing := buildIngress()
+
+	data := map[string]string{}
+	ing.SetAnnotations(data)
+
+	tests := []struct {
+		title                string
+		url                  string
+		keepaliveConnections string
+		keepaliveRequests    string
+		keepaliveTimeout     string
+		expectedConnections  int
+		expectedRequests     int
+		expectedTimeout      int
+	}{
+		{"all set", "http://goog.url", "5", "500", "50", 5, 500, 50},
+		{"no annotation", "http://goog.url", "", "", "", defaultKeepaliveConnections, defaultKeepaliveRequests, defaultKeepaliveTimeout},
+		{"default for connections", "http://goog.url", "x", "500", "50", defaultKeepaliveConnections, 500, 50},
+		{"default for requests", "http://goog.url", "5", "x", "50", 5, defaultKeepaliveRequests, 50},
+		{"default for invalid timeout", "http://goog.url", "5", "500", "x", 5, 500, defaultKeepaliveTimeout},
+		{"variable in host", "http://$host:5000/a/b", "5", "", "", 0, defaultKeepaliveRequests, defaultKeepaliveTimeout},
+		{"variable in path", "http://goog.url:5000/$path", "5", "", "", 5, defaultKeepaliveRequests, defaultKeepaliveTimeout},
+		{"negative connections", "http://goog.url", "-2", "", "", 0, defaultKeepaliveRequests, defaultKeepaliveTimeout},
+		{"negative requests", "http://goog.url", "5", "-1", "", 0, -1, defaultKeepaliveTimeout},
+		{"negative timeout", "http://goog.url", "5", "", "-1", 0, defaultKeepaliveRequests, -1},
+		{"negative request and timeout", "http://goog.url", "5", "-2", "-3", 0, -2, -3},
+	}
+
+	for _, test := range tests {
+		data[parser.GetAnnotationWithPrefix("auth-url")] = test.url
+		data[parser.GetAnnotationWithPrefix("auth-keepalive")] = test.keepaliveConnections
+		data[parser.GetAnnotationWithPrefix("auth-keepalive-timeout")] = test.keepaliveTimeout
+		data[parser.GetAnnotationWithPrefix("auth-keepalive-requests")] = test.keepaliveRequests
+
+		i, err := NewParser(&resolver.Mock{}).Parse(ing)
+		if err != nil {
+			t.Errorf("%v: unexpected error: %v", test.title, err)
+			continue
+		}
+
+		u, ok := i.(*Config)
+		if !ok {
+			t.Errorf("%v: expected an External type", test.title)
+			continue
+		}
+
+		if u.URL != test.url {
+			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.url, u.URL)
+		}
+
+		if u.KeepaliveConnections != test.expectedConnections {
+			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.expectedConnections, u.KeepaliveConnections)
+		}
+
+		if u.KeepaliveRequests != test.expectedRequests {
+			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.expectedRequests, u.KeepaliveRequests)
+		}
+
+		if u.KeepaliveTimeout != test.expectedTimeout {
+			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.expectedTimeout, u.KeepaliveTimeout)
+		}
+	}
+}
+
 func TestParseStringToCacheDurations(t *testing.T) {
 
 	tests := []struct {