Fix: Interpolate variables into MultiHTTP request bodies (#713)

Update the MultiHTTP script template to interpolate variables in the body using JS. Uses string.replace() to swap the variable placeholders with the variable value.
grafana · May 30, 2024 · bac84cb · bac84cb
1 parent 67934ee
commit bac84cb
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Showing 3 changed files with 92 additions and 8 deletions.
diff --git a/internal/prober/multihttp/script.go b/internal/prober/multihttp/script.go
@@ -105,6 +105,44 @@ func buildBody(body *sm.HttpRequestBody) string {
 	}
 }
 
+func interpolateBodyVariables(bodyVarName string, body *sm.HttpRequestBody) []string {
+	switch {
+	case body == nil || len(body.Payload) == 0:
+		return nil
+
+	default:
+		var buf strings.Builder
+
+		matches := userVariables.FindAllString(string(body.Payload), -1)
+		parsedMatches := make(map[string]struct{})
+		out := make([]string, 0, len(matches))
+
+		// For every instance of ${variable} in the body,
+		// this block returns {bodyVarName}.replace('${variable}', vars['variable'])
+		for _, m := range matches {
+			if _, found := parsedMatches[m]; found {
+				continue
+			}
+
+			buf.Reset()
+			buf.WriteString(bodyVarName)
+			buf.WriteString(".replace('")
+			buf.WriteString(m)
+			buf.WriteString("', vars['")
+			// writing the variable name from between ${ and }
+			for i := 2; i < len(m)-1; i++ {
+				buf.WriteByte(m[i])
+			}
+			buf.WriteString("'])")
+			out = append(out, buf.String())
+
+			parsedMatches[m] = struct{}{}
+		}
+
+		return out
+	}
+}
+
 func buildHeaders(headers []*sm.HttpHeader, body *sm.HttpRequestBody) string {
 	var buf strings.Builder
 
@@ -387,12 +425,13 @@ func settingsToScript(settings *sm.MultiHttpSettings) ([]byte, error) {
 	tmpl, err := template.
 		New("").
 		Funcs(template.FuncMap{
-			"buildBody":        buildBody,
-			"buildChecks":      buildChecks,
-			"buildHeaders":     buildHeaders,
-			"buildUrl":         performVariableExpansion,
-			"buildQueryParams": buildQueryParams,
-			"buildVars":        buildVars,
+			"buildBody":           buildBody,
+			"buildChecks":         buildChecks,
+			"buildHeaders":        buildHeaders,
+			"buildUrl":            performVariableExpansion,
+			"buildQueryParams":    buildQueryParams,
+			"buildVars":           buildVars,
+			"interpolateBodyVars": interpolateBodyVariables,
 		}).
 		ParseFS(templateFS, "*.tmpl")
 	if err != nil {

diff --git a/internal/prober/multihttp/script.tmpl b/internal/prober/multihttp/script.tmpl
@@ -69,6 +69,7 @@ function assertHeader(headers, name, matcher) {
 
 export default function() {
 	let response;
+	let body;
 	let url;
 	let currentCheck;
 	let match;
@@ -87,9 +88,14 @@ export default function() {
 	{{ range $queries }}{{ . }};
 	{{ end -}}
 	{{- $method := .Request.Method.String }}
-	{{- $body := buildBody .Request.Body }}
+
+	body = {{ buildBody .Request.Body }};
+	{{- $bodyVars := interpolateBodyVars "body" .Request.Body }}
+	{{ range $bodyVars }}{{ . }};
+	{{ end -}}
+
 	{{- $headers := buildHeaders .Request.Headers .Request.Body }}
-	response = http.request('{{ $method }}', url.toString(), {{ $body }}, {
+	response = http.request('{{ $method }}', url.toString(), body, {
 		// TODO(mem): build params out of options for the check
 		tags: {
 		  name: '{{ $idx }}', // TODO(mem): give the user some control over this?

diff --git a/internal/prober/multihttp/script_test.go b/internal/prober/multihttp/script_test.go
@@ -342,6 +342,45 @@ func TestBuildBody(t *testing.T) {
 	}
 }
 
+func TestInterpolateBodyVariables(t *testing.T) {
+	t.Parallel()
+
+	type input struct {
+		body *sm.HttpRequestBody
+	}
+
+	testcases := map[string]struct {
+		input    input
+		expected []string
+	}{
+		"no variables": {
+			input:    input{body: &sm.HttpRequestBody{Payload: []byte("test")}},
+			expected: []string{},
+		},
+		"basic": {
+			input: input{body: &sm.HttpRequestBody{Payload: []byte("test ${variable1}")}},
+			expected: []string{
+				"body.replace('${variable1}', vars['variable1'])",
+			},
+		},
+		"several variables with repeats": {
+			input: input{body: &sm.HttpRequestBody{Payload: []byte("${variable1} is ${variable1} fun ${variable2} ok ${variable3}")}},
+			expected: []string{
+				"body.replace('${variable1}', vars['variable1'])",
+				"body.replace('${variable2}', vars['variable2'])",
+				"body.replace('${variable3}', vars['variable3'])",
+			},
+		},
+	}
+	for name, tc := range testcases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			actual := interpolateBodyVariables("body", tc.input.body)
+			require.Equal(t, tc.expected, actual)
+		})
+	}
+}
+
 func TestAssertionConditionName(t *testing.T) {
 	testcases := map[string]struct {
 		condition sm.MultiHttpEntryAssertionConditionVariant