exporter: allow to specify the path to ccache

Signed-off-by: VirtualTam <[email protected]>

cmd/ccache_exporter/main.go

@@ -29,9 +29,15 @@ const (
 
 func main() {
 	listenAddr := flag.String("listenAddr", DefaultListenAddr, "Listen on this address")
+	ccacheBinaryPath := flag.String("ccacheBinaryPath", ccache.DefaultBinaryPath, "Path to the ccache binary")
 	flag.Parse()
 
-	collector := ccache.NewCollector()
+	wrapper, err := ccache.NewBinaryWrapper(*ccacheBinaryPath)
+	if err != nil {
+		log.Fatal(err)
+	}
+	collector := ccache.NewCollector(wrapper)
+
 	prometheus.MustRegister(collector)
 
 	http.Handle("/metrics", promhttp.Handler())

collector.go

@@ -6,7 +6,6 @@ package ccache
 
 import (
 	"log"
-	"os/exec"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -16,6 +15,8 @@ const (
 )
 
 type collector struct {
+	wrapper Wrapper
+
 	call                     *prometheus.Desc
 	callHit                  *prometheus.Desc
 	cacheHitRatio            *prometheus.Desc
@@ -31,8 +32,9 @@ type collector struct {
 
 // NewCollector initializes and returns a Prometheus collector for ccache
 // metrics.
-func NewCollector() *collector {
+func NewCollector(w Wrapper) *collector {
 	return &collector{
+		wrapper: w,
 		call: prometheus.NewDesc(
 			prometheus.BuildFQName(namespace, "", "call_total"),
 			"Cache calls (total)",
@@ -120,13 +122,13 @@ func (c *collector) Describe(ch chan<- *prometheus.Desc) {
 
 // Collect gathers metrics from ccache.
 func (c *collector) Collect(ch chan<- prometheus.Metric) {
-	out, err := exec.Command("ccache", "-s").Output()
+	out, err := c.wrapper.ShowStats()
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	stats := Statistics{}
-	stats.Parse(string(out[:]))
+	stats.Parse(string(out))
 
 	// counters
 	ch <- prometheus.MustNewConstMetric(

wrapper.go

@@ -0,0 +1,53 @@
+// Copyright 2018 VirtualTam.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package ccache
+
+import "os/exec"
+
+const (
+	DefaultBinaryPath = "/usr/bin/ccache"
+)
+
+// Wrapper exposes supported ccache commands.
+type Wrapper interface {
+	ShowStats() (string, error)
+	Version() (string, error)
+}
+
+// BinaryWrapper runs ccache commands locally.
+type BinaryWrapper struct {
+	path string
+}
+
+func (w *BinaryWrapper) exec(option string) (string, error) {
+	out, err := exec.Command(w.path, option).Output()
+
+	if err != nil {
+		return "", err
+	}
+
+	return string(out[:]), nil
+}
+
+// ShowStats returns the result of ``ccache --show-stats''.
+func (w *BinaryWrapper) ShowStats() (string, error) {
+	return w.exec("--show-stats")
+}
+
+// Version returns the result of ``ccache --version''.
+func (w *BinaryWrapper) Version() (string, error) {
+	return w.exec("--version")
+}
+
+// NewBinaryWrapper ensures the ccache executable exists and can be invoked, and
+// returns an initialized BinaryWrapper.
+func NewBinaryWrapper(path string) (*BinaryWrapper, error) {
+	err := exec.Command(path, "-s").Run()
+	if err != nil {
+		return &BinaryWrapper{}, err
+	}
+
+	return &BinaryWrapper{path: path}, nil
+}