Heartbeat support options for lightweight checks (#32987)

Fixes #32457 by adding support for this HTTP verb

Co-authored-by: debadair <debadair@elastic.co>
Co-authored-by: Xiao, Lowry <fenxiao@ebay.com>

heartbeat/docs/monitors/monitor-http.asciidoc

@@ -133,8 +133,8 @@ Example configuration:
 
 Under `check.request`, specify these options:
 
-*`method`*:: The HTTP method to use. Valid values are `"HEAD"`, `"GET"` and
-`"POST"`.
+*`method`*:: The HTTP method to use. Valid values are `"HEAD"`, `"GET"`, `"POST"` and
+`"OPTIONS"`.
 *`headers`*:: A dictionary of additional HTTP headers to send. By default heartbeat
 will set the 'User-Agent' header to identify itself.
 *`body`*:: Optional request body content.

heartbeat/monitors/active/http/config.go

@@ -137,7 +137,7 @@ func (r *responseConfig) Validate() error {
 // Validate validates of the requestParameters object is valid or not
 func (r *requestParameters) Validate() error {
 	switch strings.ToUpper(r.Method) {
-	case "HEAD", "GET", "POST":
+	case "HEAD", "GET", "POST", "OPTIONS":
 	default:
 		return fmt.Errorf("HTTP method '%v' not supported", r.Method)
 	}

heartbeat/tests/system/config/heartbeat.yml.j2

@@ -33,6 +33,9 @@ heartbeat.monitors:
     {% endfor %}
   {% endif -%}
 
+  {%- if monitor.check_request_method is defined %}
+  check.request.method: {{monitor.check_request_method}}
+  {% endif -%}
 
   {%- if monitor.check_response_json is defined %}
   check.response.json:

heartbeat/tests/system/heartbeat.py

@@ -26,7 +26,20 @@ def do_GET(self):
 
                 self.wfile.write(bytes(content, "utf-8"))
 
+        # set up a HTTPHandler that supports OPTIONS method as well
+        class HTTPHandlerEnabledOPTIONS(HTTPHandler):
+            def do_OPTIONS(self):
+                self.send_response(status_code)
+                self.send_header('Access-Control-Allow-Credentials', 'true')
+                self.send_header('Access-Control-Allow-Origin', '*')
+                self.send_header('Access-Control-Allow-Methods', 'HEAD, GET, POST, OPTIONS')
+                self.end_headers()
+
+        # initialize http server based on if it needs to support OPTIONS method
         server = http.server.HTTPServer(('localhost', 0), HTTPHandler)
+        # setup enable_options_method as False if it's not set
+        if kwargs.get("enable_options_method", False):
+            server = http.server.HTTPServer(('localhost', 0), HTTPHandlerEnabledOPTIONS)
 
         thread = threading.Thread(target=server.serve_forever)
         thread.start()

heartbeat/tests/system/test_monitor.py

@@ -67,6 +67,44 @@ def test_http_with_hosts_config(self, status_code):
             raise unittest.SkipTest
         self.assert_fields_are_documented(output[0])
 
+    @parameterized.expand([
+        # enable_options_method
+        (lambda enable_options: True, 200),
+        (lambda enable_options: False, 501),
+    ])
+    def test_http_check_with_options_method(self, enable_options, status_code):
+        """
+        Test http server if it supports OPTIONS method check
+        """
+        # get enable_options value from parameterized decorator
+        enable_options = enable_options(enable_options)
+        status_code = int(status_code)
+        server = self.start_server("hello world", status_code,
+                                   enable_options_method=enable_options)
+
+        self.render_http_config_with_options_method(
+            ["localhost:{}".format(server.server_port)])
+
+        proc = self.start_beat()
+        self.wait_until(lambda: self.log_contains("heartbeat is running"))
+
+        self.wait_until(
+            lambda: self.output_has(lines=1))
+
+        proc.check_kill_and_wait()
+
+        server.shutdown()
+        output = self.read_output()
+        assert status_code == output[0]["http.response.status_code"]
+        if enable_options:
+            # make sure OPTIONS is in the allowed methods from the response
+            assert -1 != output[0]["http.response.headers.Access-Control-Allow-Methods"].find("OPTIONS")
+
+        if os.name == "nt":
+            # Currently skipped on Windows as fields.yml not generated
+            raise unittest.SkipTest
+        self.assert_fields_are_documented(output[0])
+
     def test_http_delayed(self):
         """
         Ensure that the HTTP monitor consumes the whole body.
@@ -143,3 +181,12 @@ def render_http_config_with_hosts(self, urls):
                 "hosts": urls,
             }]
         )
+
+    def render_http_config_with_options_method(self, urls):
+        self.render_config_template(
+            monitors=[{
+                "type": "http",
+                "hosts": urls,
+                "check_request_method": "OPTIONS",
+            }]
+        )