Test node_exporter for file descriptor leaks

node_exporter_test.go

@@ -0,0 +1,98 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+	"os/exec"
+	"testing"
+	"time"
+
+	"github.com/prometheus/procfs"
+)
+
+func TestFileDescriptorLeak(t *testing.T) {
+	const (
+		binary  = "./node_exporter"
+		address = "localhost:9100"
+	)
+
+	if _, err := os.Stat(binary); err != nil {
+		t.Skipf("node_exporter binary not available, try to run `make build` first: %s", err)
+	}
+	if _, err := procfs.NewStat(); err != nil {
+		t.Skipf("proc filesystem is not available, but currently required to read number of open file descriptors: %s", err)
+	}
+
+	errc := make(chan error)
+	exporter := exec.Command(binary, "-web.listen-address", address)
+	go func() {
+		if err := exporter.Run(); err != nil {
+			errc <- fmt.Errorf("execution of node_exporter failed: %s", err)
+		} else {
+			errc <- nil
+		}
+	}()
+
+	select {
+	case err := <-errc:
+		t.Fatal(err)
+	case <-time.After(100 * time.Millisecond):
+	}
+
+	go func(pid int, url string) {
+		if err := queryExporter(url); err != nil {
+			errc <- err
+			return
+		}
+		proc, err := procfs.NewProc(pid)
+		if err != nil {
+			errc <- err
+			return
+		}
+		fdsBefore, err := proc.FileDescriptors()
+		if err != nil {
+			errc <- err
+			return
+		}
+		for i := 0; i < 5; i++ {
+			if err := queryExporter(url); err != nil {
+				errc <- err
+				return
+			}
+		}
+		fdsAfter, err := proc.FileDescriptors()
+		if err != nil {
+			errc <- err
+			return
+		}
+		if want, have := len(fdsBefore), len(fdsAfter); want != have {
+			errc <- fmt.Errorf("want %d open file descriptors after metrics scrape, have %d", want, have)
+		}
+		errc <- nil
+	}(exporter.Process.Pid, fmt.Sprintf("http://%s/metrics", address))
+
+	select {
+	case err := <-errc:
+		if exporter.Process != nil {
+			exporter.Process.Kill()
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func queryExporter(url string) error {
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	if err := resp.Body.Close(); err != nil {
+		return err
+	}
+	if want, have := resp.StatusCode, http.StatusOK; want != have {
+		return fmt.Errorf("want /metrics status code %d, have %d", want, have)
+	}
+	return nil
+}