Adds a flag to control if the prog label is emitted by exporters.

Returns the emission of the prometheus prog label, unless activated by this
flag.  Varz also changes behaviour.  The other push exporters are not modified
as the prog label is intrinsic to their formats (at the moment.)

Fixes #59

exporter/export.go

@@ -28,15 +28,16 @@ var (
 // Exporter manages the export of metrics to passive and active collectors.
 type Exporter struct {
 	store       *metrics.Store
-	hostname    string
+	o           Options
 	pushTargets []pushOptions
 }
 
 // Options contains the required and optional parameters for constructing an
 // Exporter.
 type Options struct {
-	Store    *metrics.Store
-	Hostname string // Not required, uses os.Hostname if zero.
+	Store         *metrics.Store
+	Hostname      string // Not required, uses os.Hostname if zero.
+	OmitProgLabel bool   // If true, don't emit the prog label that identifies the source program in variable exports.
 }
 
 // New creates a new Exporter.
@@ -52,7 +53,7 @@ func New(o Options) (*Exporter, error) {
 			return nil, fmt.Errorf("Error getting hostname: %s\n", err)
 		}
 	}
-	e := &Exporter{store: o.Store, hostname: hostname}
+	e := &Exporter{store: o.Store, o: o}
 
 	if *collectdSocketPath != "" {
 		o := pushOptions{"unix", *collectdSocketPath, metricToCollectd, collectdExportTotal, collectdExportSuccess}
@@ -100,7 +101,7 @@ func (e *Exporter) writeSocketMetrics(c net.Conn, f formatter, exportTotal *expv
 			lc := make(chan *metrics.LabelSet)
 			go m.EmitLabelSets(lc)
 			for l := range lc {
-				line := f(e.hostname, m, l)
+				line := f(e.o.Hostname, m, l)
 				n, err := fmt.Fprint(c, line)
 				glog.V(2).Infof("Sent %d bytes\n", n)
 				if err == nil {

exporter/json_test.go

@@ -95,7 +95,7 @@ func TestHandleJSON(t *testing.T) {
 			for _, metric := range tc.metrics {
 				ms.Add(metric)
 			}
-			o := Options{ms, "gunstar"}
+			o := Options{ms, "gunstar", false}
 			e, err := New(o)
 			if err != nil {
 				t.Fatalf("couldn't make exporter: %s", err)

exporter/prometheus.go

@@ -53,21 +53,24 @@ func (e *Exporter) HandlePrometheusMetrics(w http.ResponseWriter, r *http.Reques
 				if m.Source != "" {
 					fmt.Fprintf(w, "# %s defined at %s\n", noHyphens(m.Name), m.Source)
 				}
-				line := metricToPrometheus(e.hostname, m, l)
+				line := metricToPrometheus(e.o, m, l)
 				fmt.Fprint(w, line)
 			}
 			m.RUnlock()
 		}
 	}
 }
 
-func metricToPrometheus(hostname string, m *metrics.Metric, l *metrics.LabelSet) string {
+func metricToPrometheus(options Options, m *metrics.Metric, l *metrics.LabelSet) string {
 	var s []string
 	for k, v := range l.Labels {
 		// Prometheus quotes the value of each label=value pair.
 		s = append(s, fmt.Sprintf("%s=%q", k, v))
 	}
 	sort.Strings(s)
+	if !options.OmitProgLabel {
+		s = append(s, fmt.Sprintf("prog=\"%s\"", m.Program))
+	}
 	return fmt.Sprintf(prometheusFormat,
 		noHyphens(m.Name),
 		strings.Join(s, ","),

exporter/prometheus_test.go

@@ -137,7 +137,7 @@ func TestHandlePrometheus(t *testing.T) {
 			for _, metric := range tc.metrics {
 				ms.Add(metric)
 			}
-			o := Options{ms, "gunstar"}
+			o := Options{ms, "gunstar", true}
 			e, err := New(o)
 			if err != nil {
 				t.Fatalf("couldn't make exporter: %s", err)

exporter/varz.go

@@ -33,22 +33,24 @@ func (e *Exporter) HandleVarz(w http.ResponseWriter, r *http.Request) {
 			lc := make(chan *metrics.LabelSet)
 			go m.EmitLabelSets(lc)
 			for l := range lc {
-				line := metricToVarz(e.hostname, m, l)
+				line := metricToVarz(e.o, m, l)
 				fmt.Fprint(w, line)
 			}
 			m.RUnlock()
 		}
 	}
 }
 
-func metricToVarz(hostname string, m *metrics.Metric, l *metrics.LabelSet) string {
+func metricToVarz(o Options, m *metrics.Metric, l *metrics.LabelSet) string {
 	var s []string
 	for k, v := range l.Labels {
 		s = append(s, fmt.Sprintf("%s=%s", k, v))
 	}
 	sort.Strings(s)
-	s = append(s, fmt.Sprintf("prog=%s", m.Program))
-	s = append(s, fmt.Sprintf("instance=%s", hostname))
+	if !o.OmitProgLabel {
+		s = append(s, fmt.Sprintf("prog=%s", m.Program))
+	}
+	s = append(s, fmt.Sprintf("instance=%s", o.Hostname))
 	return fmt.Sprintf(varzFormat,
 		m.Name,
 		strings.Join(s, ","),

exporter/varz_test.go

@@ -59,7 +59,7 @@ func TestHandleVarz(t *testing.T) {
 			for _, metric := range tc.metrics {
 				ms.Add(metric)
 			}
-			o := Options{ms, "gunstar"}
+			o := Options{ms, "gunstar", false}
 			e, err := New(o)
 			if err != nil {
 				t.Fatalf("couldn't make exporter: %s", err)

main.go

@@ -54,14 +54,17 @@ var (
 	port  = flag.String("port", "3903", "HTTP port to listen on.")
 	progs = flag.String("progs", "", "Name of the directory containing mtail programs")
 
+	// Compiler behaviour flags
 	oneShot        = flag.Bool("one_shot", false, "Run the contents of the provided logs until EOF and exit.")
 	oneShotMetrics = flag.Bool("one_shot_metrics", false, "Dump metrics (to stdout) after one shot mode.")
 	compileOnly    = flag.Bool("compile_only", false, "Compile programs only, do not load the virtual machine.")
 	dumpAst        = flag.Bool("dump_ast", false, "Dump AST of programs after parse (to INFO log).")
 	dumpAstTypes   = flag.Bool("dump_ast_types", false, "Dump AST of programs with type annotation after typecheck (to INFO log).")
 	dumpBytecode   = flag.Bool("dump_bytecode", false, "Dump bytecode of programs (to INFO log).")
 
+	// Runtime behaviour flags
 	syslogUseCurrentYear = flag.Bool("syslog_use_current_year", true, "Patch yearless timestamps with the present year.")
+	emitProgLabel        = flag.Bool("emit_prog_label", true, "Emit the 'prog' label in variable exports.")
 )
 
 func init() {
@@ -108,6 +111,7 @@ func main() {
 		DumpAstTypes:         *dumpAstTypes,
 		DumpBytecode:         *dumpBytecode,
 		SyslogUseCurrentYear: *syslogUseCurrentYear,
+		OmitProgLabel:        !*emitProgLabel,
 		BuildInfo:            buildInfo(),
 	}
 	m, err := mtail.New(o)

mtail/mtail.go

@@ -200,6 +200,7 @@ type Options struct {
 	DumpBytecode         bool
 	SyslogUseCurrentYear bool
 	OmitMetricSource     bool
+	OmitProgLabel        bool
 
 	BuildInfo string
 
@@ -226,7 +227,7 @@ func New(o Options) (*MtailServer, error) {
 		return nil, err
 	}
 
-	m.e, err = exporter.New(exporter.Options{Store: m.store})
+	m.e, err = exporter.New(exporter.Options{Store: m.store, OmitProgLabel: o.OmitProgLabel})
 	if err != nil {
 		return nil, err
 	}