Merge pull request #4 from cloudflare/allow_dynamic_target

Allow OpenTSDB URL to be set at scrape time
cloudflare · Jun 29, 2017 · 7ba7191 · 7ba7191
2 parents 4c033e2 + 96f3290
commit 7ba7191
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Showing 2 changed files with 39 additions and 27 deletions.
diff --git a/main.go b/main.go
@@ -12,25 +12,27 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/log"
 )
 
-const applicationName = "opentsdb_exporter"
+const (
+	applicationName = "opentsdb_exporter"
+	metricsRoute    = "/metrics"
+	probeRoute      = "/opentsdb"
+)
 
 var (
 	nameSanitiser = strings.NewReplacer("tsd.", "opentsdb_", ".", "_", "-", "_")
 	revision      = "unknown"
+
+	versionString = fmt.Sprintf("%s %s (%s)", applicationName, revision, runtime.Version())
+	showVersion   = flag.Bool("version", false, "Print version information.")
+	listenAddress = flag.String("web.listen-address", ":9250", "Address to listen on for web interface and telemetry.")
+	timeout       = flag.Duration("opentsdb.timeout", 5*time.Second, "Timeout for HTTP requests to OpenTSDB.")
 )
 
 func main() {
-	var (
-		versionString = fmt.Sprintf("%s %s (%s)", applicationName, revision, runtime.Version())
-		showVersion   = flag.Bool("version", false, "Print version information.")
-		listenAddress = flag.String("web.listen-address", ":9250", "Address to listen on for web interface and telemetry.")
-		metricsPath   = flag.String("web.telemetry-path", "/metrics", "Path under which to expose metrics.")
-		url           = flag.String("opentsdb.url", "http://localhost:4242", "HTTP URL for OpenTSDB server to monitor.")
-		timeout       = flag.Duration("opentsdb.timeout", 5*time.Second, "Timeout for HTTP requests to OpenTSDB.")
-	)
 
 	flag.Parse()
 
@@ -41,16 +43,15 @@ func main() {
 
 	log.Infoln("Starting", versionString)
 
-	exporter := newExporter(*url, *timeout)
-	prometheus.MustRegister(exporter)
-
-	http.Handle(*metricsPath, prometheus.Handler())
+	http.Handle(metricsRoute, promhttp.Handler())
+	http.HandleFunc("/opentsdb", handler)
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte(`<html>
 		<head><title>OpenTSDB Exporter</title></head>
 		<body>
 		<h1>` + versionString + `</h1>
-		<p><a href='` + *metricsPath + `'>Metrics</a></p>
+		<p><a href='` + metricsRoute + `'>Metrics</a></p>
+		<p><a href='` + probeRoute + `?target=http://opentsdb.localhost'>Example OpenTSDB probe</a></p>
 		</body>
 		</html>`))
 	})
@@ -65,26 +66,37 @@ func main() {
 	log.Fatal(s.ListenAndServe())
 }
 
-type exporter struct {
-	url     string
+type collector struct {
+	target  string
 	timeout time.Duration
 }
 
-func newExporter(url string, timeout time.Duration) *exporter {
-	return &exporter{url, timeout}
+func handler(w http.ResponseWriter, r *http.Request) {
+	target := r.URL.Query().Get("target")
+	if target == "" {
+		http.Error(w, "'target' parameter must be specified", 400)
+		return
+	}
+
+	log.Debugf("Scraping target %q", target)
+	registry := prometheus.NewRegistry()
+	registry.MustRegister(&collector{target: target, timeout: *timeout})
+
+	h := promhttp.HandlerFor(registry, promhttp.HandlerOpts{})
+	h.ServeHTTP(w, r)
 }
 
-func (e *exporter) Collect(ch chan<- prometheus.Metric) {
-	metrics, err := e.queryOpenTSDB()
+func (c *collector) Collect(ch chan<- prometheus.Metric) {
+	metrics, err := c.queryOpenTSDB()
 	if err != nil {
-		log.Errorf("Error scraping target %s: %s", e.url, err)
+		log.Errorf("Error scraping target %s: %s", c.target, err)
 		ch <- prometheus.NewInvalidMetric(prometheus.NewDesc("api_error", "Error scraping target", nil, nil), err)
 		return
 	}
 	for _, m := range *metrics {
 		value, err := m.Value.Float64()
 		if err != nil {
-			log.Errorf("Error scraping target %s: %s", e.url, err)
+			log.Errorf("Error scraping target %s: %s", c.target, err)
 			ch <- prometheus.NewInvalidMetric(prometheus.NewDesc("api_error", "Error scraping target", nil, nil), err)
 			return
 		}
@@ -109,17 +121,17 @@ func (e *exporter) Collect(ch chan<- prometheus.Metric) {
 	}
 }
 
-func (e *exporter) Describe(ch chan<- *prometheus.Desc) {
+func (c *collector) Describe(ch chan<- *prometheus.Desc) {
 	// Copied from https://github.com/prometheus/snmp_exporter/blob/bc4b0a4db1e22c5379f7fdb3f314dbb58a48c637/collector.go#L118
 	ch <- prometheus.NewDesc("dummy", "dummy", nil, nil)
 }
 
-func (e *exporter) queryOpenTSDB() (m *metrics, err error) {
+func (c *collector) queryOpenTSDB() (m *metrics, err error) {
 	client := &http.Client{
-		Timeout: e.timeout,
+		Timeout: c.timeout,
 	}
 
-	resp, err := client.Get(e.url + "/api/stats")
+	resp, err := client.Get(c.target + "/api/stats")
 	if err != nil {
 		return m, err
 	}

diff --git a/main_test.go b/main_test.go
@@ -38,7 +38,7 @@ func TestHappyPath(t *testing.T) {
 	}))
 	defer ts.Close()
 
-	e := newExporter(ts.URL, 5*time.Second)
+	e := &collector{target: ts.URL, timeout: 5 * time.Second}
 	ch := make(chan prometheus.Metric)
 	go e.Collect(ch)