Add metrics for GitHub API rate limit (#312)

github/github.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/bradleyfalzon/ghinstallation"
 	"github.com/google/go-github/v33/github"
+	"github.com/summerwind/actions-runner-controller/github/metrics"
 	"golang.org/x/oauth2"
 )
 
@@ -34,15 +35,9 @@ type Client struct {
 
 // NewClient creates a Github Client
 func (c *Config) NewClient() (*Client, error) {
-	var (
-		httpClient *http.Client
-		client     *github.Client
-	)
-	githubBaseURL := "https://github.com/"
+	var transport http.RoundTripper
 	if len(c.Token) > 0 {
-		httpClient = oauth2.NewClient(context.Background(), oauth2.StaticTokenSource(
-			&oauth2.Token{AccessToken: c.Token},
-		))
+		transport = oauth2.NewClient(context.Background(), oauth2.StaticTokenSource(&oauth2.Token{AccessToken: c.Token})).Transport
 	} else {
 		tr, err := ghinstallation.NewKeyFromFile(http.DefaultTransport, c.AppID, c.AppInstallationID, c.AppPrivateKey)
 		if err != nil {
@@ -55,9 +50,13 @@ func (c *Config) NewClient() (*Client, error) {
 			}
 			tr.BaseURL = githubAPIURL
 		}
-		httpClient = &http.Client{Transport: tr}
+		transport = tr
 	}
+	transport = metrics.Transport{Transport: transport}
+	httpClient := &http.Client{Transport: transport}
 
+	var client *github.Client
+	var githubBaseURL string
 	if len(c.EnterpriseURL) > 0 {
 		var err error
 		client, err = github.NewEnterpriseClient(c.EnterpriseURL, c.EnterpriseURL, httpClient)
@@ -67,6 +66,7 @@ func (c *Config) NewClient() (*Client, error) {
 		githubBaseURL = fmt.Sprintf("%s://%s%s", client.BaseURL.Scheme, client.BaseURL.Host, strings.TrimSuffix(client.BaseURL.Path, "api/v3/"))
 	} else {
 		client = github.NewClient(httpClient)
+		githubBaseURL = "https://github.com/"
 	}
 
 	return &Client{

github/metrics/transport.go

@@ -0,0 +1,63 @@
+// Package metrics provides monitoring of the GitHub related metrics.
+//
+// This depends on the metrics exporter of kubebuilder.
+// See https://book.kubebuilder.io/reference/metrics.html for details.
+package metrics
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+func init() {
+	metrics.Registry.MustRegister(metricRateLimit, metricRateLimitRemaining)
+}
+
+var (
+	// https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting
+	metricRateLimit = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name: "github_rate_limit",
+			Help: "The maximum number of requests you're permitted to make per hour",
+		},
+	)
+	metricRateLimitRemaining = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Name: "github_rate_limit_remaining",
+			Help: "The number of requests remaining in the current rate limit window",
+		},
+	)
+)
+
+const (
+	// https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting
+	headerRateLimit          = "X-RateLimit-Limit"
+	headerRateLimitRemaining = "X-RateLimit-Remaining"
+)
+
+// Transport wraps a transport with metrics monitoring
+type Transport struct {
+	Transport http.RoundTripper
+}
+
+func (t Transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	resp, err := t.Transport.RoundTrip(req)
+	if resp != nil {
+		parseResponse(resp)
+	}
+	return resp, err
+}
+
+func parseResponse(resp *http.Response) {
+	rateLimit, err := strconv.Atoi(resp.Header.Get(headerRateLimit))
+	if err == nil {
+		metricRateLimit.Set(float64(rateLimit))
+	}
+	rateLimitRemaining, err := strconv.Atoi(resp.Header.Get(headerRateLimitRemaining))
+	if err == nil {
+		metricRateLimitRemaining.Set(float64(rateLimitRemaining))
+	}
+}

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/onsi/ginkgo v1.8.0
 	github.com/onsi/gomega v1.5.0
+	github.com/prometheus/client_golang v0.9.2
 	github.com/stretchr/testify v1.4.0 // indirect
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
 	k8s.io/api v0.0.0-20190918155943-95b840bb6a1f