review

internal/adhoc/adhoc.go

@@ -139,7 +139,7 @@ func NewHandler(opts HandlerOpts) (*Handler, error) {
 		tenantCh:                     opts.TenantCh,
 		runnerFactory:                opts.runnerFactory,
 		grpcAdhocChecksClientFactory: opts.grpcAdhocChecksClientFactory,
-		proberFactory:                prober.NewProberFactory(opts.K6Runner, ""),
+		proberFactory:                prober.NewProberFactory(opts.K6Runner, 0),
 		api: apiInfo{
 			conn: opts.Conn,
 		},

internal/prober/http/http.go

@@ -264,16 +264,23 @@ func augmentHttpHeaders(check *sm.Check, reservedHeaders http.Header) {
 	for _, header := range check.Settings.Http.Headers {
 		name, _ := strToHeaderNameValue(header)
 
-		_, present := reservedHeaders[strings.ToLower(name)]
+		_, present := reservedHeaders[http.CanonicalHeaderKey(name)]
 		if present {
 			continue // users can't override reserved headers with their own values
 		}
 
 		headers = append(headers, header)
 	}
 
-	for header, values := range reservedHeaders {
-		headers = append(headers, fmt.Sprintf("%s:%s", header, strings.Join(values, ",")))
+	for key, values := range reservedHeaders {
+		var b strings.Builder
+		for _, value := range values {
+			b.Reset()
+			b.WriteString(key)
+			b.WriteRune(':')
+			b.WriteString(value)
+			headers = append(headers, b.String())
+		}
 	}
 
 	check.Settings.Http.Headers = headers

internal/prober/http/http_test.go

@@ -46,7 +46,7 @@ func TestNewProber(t *testing.T) {
 			},
 			expected: Prober{
 				config: getDefaultModule().
-					addHttpHeader("x-sm-id", "3-3"). // is checkId twice since probeId is unavailable here
+					addHttpHeader("X-Sm-Id", "3-3"). // is checkId twice since probeId is unavailable here
 					getConfigModule(),
 			},
 			ExpectError: false,
@@ -80,7 +80,7 @@ func TestNewProber(t *testing.T) {
 				config: getDefaultModule().
 					addHttpHeader("uSeR-aGeNt", "test-user-agent").
 					addHttpHeader("some-header", "some-value").
-					addHttpHeader("x-sm-id", "5-5").
+					addHttpHeader("X-Sm-Id", "5-5").
 					getConfigModule(),
 			},
 			ExpectError: false,
@@ -94,7 +94,7 @@ func TestNewProber(t *testing.T) {
 			// origin identifier for http requests is checkId-probeId; testing with checkId twice in the absence of probeId
 			checkId := testcase.input.Id
 			reservedHeaders := http.Header{}
-			reservedHeaders["x-sm-id"] = []string{fmt.Sprintf("%d-%d", checkId, checkId)}
+			reservedHeaders.Add("x-sm-id", fmt.Sprintf("%d-%d", checkId, checkId))
 
 			actual, err := NewProber(ctx, testcase.input, logger, reservedHeaders)
 			require.Equal(t, &testcase.expected, &actual)

internal/prober/multihttp/multihttp.go

@@ -105,7 +105,7 @@ func augmentHttpHeaders(check *sm.Check, reservedHeaders http.Header) {
 	for _, entry := range check.Settings.Multihttp.Entries {
 		heads := entry.Request.Headers
 		for _, headerPtr := range heads {
-			_, present := reservedHeaders[strings.ToLower(headerPtr.Name)]
+			_, present := reservedHeaders[http.CanonicalHeaderKey(headerPtr.Name)]
 
 			if present {
 				continue // users can't override reserved headers with their own values

internal/prober/multihttp/multihttp_test.go

@@ -116,7 +116,7 @@ func TestNewProber(t *testing.T) {
 			var runner noopRunner
 			checkId := tc.check.Id
 			reservedHeaders := http.Header{}
-			reservedHeaders["x-sm-id"] = []string{fmt.Sprintf("%d-%d", checkId, checkId)}
+			reservedHeaders.Add("x-sm-id", fmt.Sprintf("%d-%d", checkId, checkId))
 
 			p, err := NewProber(ctx, tc.check, logger, runner, reservedHeaders)
 			if tc.expectFailure {
@@ -127,7 +127,7 @@ func TestNewProber(t *testing.T) {
 			requestHeaders := tc.check.Settings.Multihttp.Entries[0].Request.Headers
 			require.Equal(t, len(requestHeaders), 1) // reserved header is present
 
-			require.Equal(t, requestHeaders[0].Name, "x-sm-id")
+			require.Equal(t, requestHeaders[0].Name, "X-Sm-Id")
 			require.Equal(t, requestHeaders[0].Value, fmt.Sprintf("%d-%d", checkId, checkId))
 
 			require.NoError(t, err)

internal/prober/prober.go

@@ -35,14 +35,14 @@ type ProberFactory interface {
 }
 
 type proberFactory struct {
-	runner               k6runner.Runner
-	checkProbeIdentifier string
+	runner  k6runner.Runner
+	probeId int64
 }
 
-func NewProberFactory(runner k6runner.Runner, checkProbeIdentifier string) ProberFactory {
+func NewProberFactory(runner k6runner.Runner, probeId int64) ProberFactory {
 	return proberFactory{
-		runner:               runner,
-		checkProbeIdentifier: checkProbeIdentifier,
+		runner:  runner,
+		probeId: probeId,
 	}
 }
 
@@ -53,17 +53,13 @@ func (f proberFactory) New(ctx context.Context, logger zerolog.Logger, check mod
 		err    error
 	)
 
-	reservedHeaders := http.Header{}
-	if f.checkProbeIdentifier != "" {
-		reservedHeaders["x-sm-id"] = []string{f.checkProbeIdentifier} // avoiding Add() to bypass canonicalization of the key
-	}
-
 	switch checkType := check.Type(); checkType {
 	case sm.CheckTypePing:
 		p, err = icmp.NewProber(check.Check)
 		target = check.Target
 
 	case sm.CheckTypeHttp:
+		reservedHeaders := f.getReservedHeaders(&check)
 		p, err = httpProber.NewProber(ctx, check.Check, logger, reservedHeaders)
 		target = check.Target
 
@@ -89,6 +85,7 @@ func (f proberFactory) New(ctx context.Context, logger zerolog.Logger, check mod
 
 	case sm.CheckTypeMultiHttp:
 		if f.runner != nil {
+			reservedHeaders := f.getReservedHeaders(&check)
 			p, err = multihttp.NewProber(ctx, check.Check, logger, f.runner, reservedHeaders)
 			target = check.Target
 		} else {
@@ -105,3 +102,14 @@ func (f proberFactory) New(ctx context.Context, logger zerolog.Logger, check mod
 
 	return p, target, err
 }
+
+// Build reserved HTTP request headers for applicable checks.
+func (f proberFactory) getReservedHeaders(check *model.Check) http.Header {
+	reservedHeaders := http.Header{}
+	if f.probeId != 0 {
+		checkProbeIdentifier := fmt.Sprintf("%d-%d", check.GlobalID(), f.probeId)
+		reservedHeaders.Add("x-sm-id", checkProbeIdentifier)
+	}
+
+	return reservedHeaders
+}

internal/scraper/scraper.go

@@ -114,14 +114,13 @@ func (d *probeData) Tenant() model.GlobalID {
 func New(ctx context.Context, check model.Check, publisher pusher.Publisher, probe sm.Probe, logger zerolog.Logger,
 	scrapeCounter Incrementer, errorCounter IncrementerVec, k6runner k6runner.Runner, labelsLimiter LabelsLimiter,
 ) (*Scraper, error) {
-	checkProbeIdentifier := fmt.Sprintf("%d-%d", check.Id, probe.Id)
 	return NewWithOpts(ctx, check, ScraperOpts{
 		Probe:         probe,
 		Publisher:     publisher,
 		Logger:        logger,
 		ScrapeCounter: scrapeCounter,
 		ErrorCounter:  errorCounter,
-		ProbeFactory:  prober.NewProberFactory(k6runner, checkProbeIdentifier),
+		ProbeFactory:  prober.NewProberFactory(k6runner, probe.Id),
 		LabelsLimiter: labelsLimiter,
 	})
 }