Add support for HTTP request body as file

Resolves #391

CONFIGURATION.md

@@ -129,7 +129,11 @@ The other placeholders are specified separately.
   [ ip_protocol_fallback: <boolean> | default = true ]
 
   # The body of the HTTP request used in probe.
-  body: [ <string> ]
+  [ body: <string> ]
+
+  # Read the HTTP request body from from a file.
+  # It is mutually exclusive with `body`.
+  [ body_file: <filename> ]
 
 ```
 

config/config.go

@@ -218,6 +218,7 @@ type HTTPProbe struct {
 	FailIfHeaderMatchesRegexp    []HeaderMatch           `yaml:"fail_if_header_matches,omitempty"`
 	FailIfHeaderNotMatchesRegexp []HeaderMatch           `yaml:"fail_if_header_not_matches,omitempty"`
 	Body                         string                  `yaml:"body,omitempty"`
+	BodyFile                     string                  `yaml:"body_file,omitempty"`
 	HTTPClientConfig             config.HTTPClientConfig `yaml:"http_client_config,inline"`
 	Compression                  string                  `yaml:"compression,omitempty"`
 	BodySizeLimit                units.Base2Bytes        `yaml:"body_size_limit,omitempty"`
@@ -330,6 +331,10 @@ func (s *HTTPProbe) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		s.HTTPClientConfig.FollowRedirects = !*s.NoFollowRedirects
 	}
 
+	if s.Body != "" && s.BodyFile != "" {
+		return errors.New("body and body_file must not both be set")
+	}
+
 	for key, value := range s.Headers {
 		switch textproto.CanonicalMIMEHeaderKey(key) {
 		case "Accept-Encoding":

prober/http.go

@@ -27,6 +27,7 @@ import (
 	"net/http/httptrace"
 	"net/textproto"
 	"net/url"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -408,6 +409,17 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
 		body = strings.NewReader(httpConfig.Body)
 	}
 
+	// If a body file is configured, add its content to the request.
+	if httpConfig.BodyFile != "" {
+		body_file, err := os.Open(httpConfig.BodyFile)
+		if err != nil {
+			level.Error(logger).Log("msg", "Error creating request", "err", err)
+			return
+		}
+		defer body_file.Close()
+		body = body_file
+	}
+
 	request, err := http.NewRequest(httpConfig.Method, targetURL.String(), body)
 	if err != nil {
 		level.Error(logger).Log("msg", "Error creating request", "err", err)

prober/http_test.go

@@ -1431,3 +1431,39 @@ func TestBody(t *testing.T) {
 		t.Fatalf("Body test failed unexpectedly.")
 	}
 }
+
+func TestBodyFile(t *testing.T) {
+	body := "Test Body"
+	tmpBodyFile, err := os.CreateTemp("", "body.txt")
+	if err != nil {
+		t.Fatalf("Error creating body tempfile: %s", err)
+	}
+	if _, err := tmpBodyFile.Write([]byte(body)); err != nil {
+		t.Fatalf("Error writing body tempfile: %s", err)
+	}
+	if err := tmpBodyFile.Close(); err != nil {
+		t.Fatalf("Error closing body tempfie: %s", err)
+	}
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		b, err := ioutil.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("Body file test failed unexpectedly.")
+		}
+		if string(b) != body {
+			t.Fatalf("Body file test failed unexpectedly.")
+		}
+	}))
+	defer ts.Close()
+
+	registry := prometheus.NewRegistry()
+	testCTX, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	result := ProbeHTTP(testCTX, ts.URL, config.Module{Timeout: time.Second, HTTP: config.HTTPProbe{
+		IPProtocolFallback: true,
+		BodyFile:           tmpBodyFile.Name(),
+	}}, registry, log.NewNopLogger())
+	if !result {
+		t.Fatalf("Body file test failed unexpectedly.")
+	}
+}