Heartbeat: control network throttling in synthetics (#28462)

* Heartbeat: control network throttling in synthetics

* Update heartbeat/docs/monitors/monitor-browser.asciidoc

Co-authored-by: Andrew Cholakian <andrew@andrewvc.com>

Co-authored-by: Andrew Cholakian <andrew@andrewvc.com>

heartbeat/docs/monitors/monitor-browser.asciidoc

@@ -164,7 +164,7 @@ Example configuration:
 ==== `ignore_https_errors`
 
 Set this option to `true` to disable TLS/SSL validation in the synthetics browser. This is useful for testing
-sites that use self-signed certs. This option can also be used to test certs from non-standard CAs, 
+sites that use self-signed certs. This option can also be used to test certs from non-standard CAs,
 though you will no longer get errors if there is anything wrong with the certificate.
 
 
@@ -175,6 +175,34 @@ though you will no longer get errors if there is anything wrong with the certifi
 Set this option to `true` to enable the normally disabled chromium sandbox.
 Defaults to false.
 
+[float]
+[[monitor-browser-throttling]]
+==== `throttling`
+
+Set this option to control the network throttling. By default, all journeys are
+run with 5Mbps download, 3Mbps upload and 20ms latency which emulates a standard
+Cabel connection.
+
+Users can control the throttling parameters, Below is an example of emulating a
+3G connection with 1.6Mbps download, 750Kbps upload and 150ms round trip time.
+
+[source,yaml]
+-------------------------------------------------------------------------------
+- type: browser
+  schedule: '@every 1m'
+  throttling: "1.6d/0.75u/150l"
+-------------------------------------------------------------------------------
+
+Network throttling can be completely disabled by passing `false`
+
+[source,yaml]
+-------------------------------------------------------------------------------
+- type: browser
+  schedule: '@every 1m'
+  throttling: false
+-------------------------------------------------------------------------------
+
+
 [float]
 [[monitor-browser-filter-journeys]]
 ==== `filter_journeys`

x-pack/heartbeat/monitors/browser/config.go

@@ -29,6 +29,7 @@ type Config struct {
 	// Id is optional for lightweight checks but required for browsers
 	Id                string                        `config:"id"`
 	Sandbox           bool                          `config:"sandbox"`
+	Throttling        interface{}                   `config:"throttling"`
 	Screenshots       string                        `config:"screenshots"`
 	SyntheticsArgs    []string                      `config:"synthetics_args"`
 	FilterJourneys    synthexec.FilterJourneyConfig `config:"filter_journeys"`

x-pack/heartbeat/monitors/browser/suite.go

@@ -85,6 +85,16 @@ func (s *Suite) extraArgs() []string {
 	if s.suiteCfg.Screenshots != "" {
 		extraArgs = append(extraArgs, "--screenshots", s.suiteCfg.Screenshots)
 	}
+	if s.suiteCfg.Throttling != nil {
+		switch t := s.suiteCfg.Throttling.(type) {
+		case bool:
+			if !t {
+				extraArgs = append(extraArgs, "--no-throttling")
+			}
+		case string:
+			extraArgs = append(extraArgs, "--throttling", fmt.Sprintf("%v", s.suiteCfg.Throttling))
+		}
+	}
 
 	return extraArgs
 }

x-pack/heartbeat/monitors/browser/suite_test.go

@@ -142,6 +142,21 @@ func TestExtraArgs(t *testing.T) {
 			&Config{Sandbox: true},
 			[]string{"--sandbox"},
 		},
+		{
+			"throttling truthy",
+			&Config{Throttling: true},
+			nil,
+		},
+		{
+			"disable throttling",
+			&Config{Throttling: false},
+			[]string{"--no-throttling"},
+		},
+		{
+			"override throttling",
+			&Config{Throttling: "10d/3u/20l"},
+			[]string{"--throttling", "10d/3u/20l"},
+		},
 		{
 			"ignore_https_errors",
 			&Config{IgnoreHTTPSErrors: true},