Fix Hetzner Robot SD decoding with non HTTP 2xx (#7872)

* Fix Hetzner Robot SD trying to decode response when a non 2xx HTTP code was returned

Signed-off-by: Lukas Kämmerling <lukas.kaemmerling@hetzner-cloud.de>

discovery/hetzner/robot.go

@@ -26,7 +26,8 @@ import (
 	"time"
 
 	"github.com/go-kit/kit/log"
-	config_util "github.com/prometheus/common/config"
+	"github.com/pkg/errors"
+	"github.com/prometheus/common/config"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/discovery/refresh"
 	"github.com/prometheus/prometheus/discovery/targetgroup"
@@ -54,7 +55,7 @@ func newRobotDiscovery(conf *SDConfig, logger log.Logger) (*robotDiscovery, erro
 		endpoint: conf.robotEndpoint,
 	}
 
-	rt, err := config_util.NewRoundTripperFromConfig(conf.HTTPClientConfig, "hetzner_sd", false, false)
+	rt, err := config.NewRoundTripperFromConfig(conf.HTTPClientConfig, "hetzner_sd", false, false)
 	if err != nil {
 		return nil, err
 	}
@@ -70,10 +71,16 @@ func (d *robotDiscovery) refresh(ctx context.Context) ([]*targetgroup.Group, err
 	if err != nil {
 		return nil, err
 	}
+
 	defer func() {
 		io.Copy(ioutil.Discard, resp.Body)
 		resp.Body.Close()
 	}()
+
+	if resp.StatusCode/100 != 2 {
+		return nil, errors.Errorf("non 2xx status '%d' response during hetzner service discovery with role robot", resp.StatusCode)
+	}
+
 	var servers serversList
 	err = json.NewDecoder(resp.Body).Decode(&servers)
 	if err != nil {

discovery/hetzner/robot_test.go

@@ -37,7 +37,6 @@ func (s *robotSDTestSuite) SetupTest(t *testing.T) {
 func TestRobotSDRefresh(t *testing.T) {
 	suite := &robotSDTestSuite{}
 	suite.SetupTest(t)
-
 	cfg := DefaultSDConfig
 	cfg.HTTPClientConfig.BasicAuth = &config.BasicAuth{Username: robotTestUsername, Password: robotTestPassword}
 	cfg.robotEndpoint = suite.Mock.Endpoint()
@@ -84,3 +83,19 @@ func TestRobotSDRefresh(t *testing.T) {
 		})
 	}
 }
+
+func TestRobotSDRefreshHandleError(t *testing.T) {
+	suite := &robotSDTestSuite{}
+	suite.SetupTest(t)
+	cfg := DefaultSDConfig
+	cfg.robotEndpoint = suite.Mock.Endpoint()
+
+	d, err := newRobotDiscovery(&cfg, log.NewNopLogger())
+	testutil.Ok(t, err)
+
+	targetGroups, err := d.refresh(context.Background())
+	testutil.NotOk(t, err)
+	testutil.Equals(t, "non 2xx status '401' response during hetzner service discovery with role robot", err.Error())
+
+	testutil.Equals(t, 0, len(targetGroups))
+}