Fix Uyuni SD initialization (#9924)

* Fix Uyuni SD initialization

The change prevents null pointer exception during SD initialization.

Signed-off-by: Witek Bedyk <witold.bedyk@suse.com>

config/config_test.go

@@ -227,7 +227,6 @@ var expectedConf = &Config{
 			},
 		},
 		{
-
 			JobName: "service-x",
 
 			HonorTimestamps: true,
@@ -954,7 +953,7 @@ var expectedConf = &Config{
 			Scheme:           DefaultScrapeConfig.Scheme,
 			ServiceDiscoveryConfigs: discovery.Configs{
 				&uyuni.SDConfig{
-					Server:          kubernetesSDHostURL(),
+					Server:          "https://localhost:1234",
 					Username:        "gopher",
 					Password:        "hole",
 					Entitlement:     "monitoring_entitled",
@@ -1434,6 +1433,10 @@ var expectedErrors = []struct {
 		filename: "empty_scrape_config_action.bad.yml",
 		errMsg:   "relabel action cannot be empty",
 	},
+	{
+		filename: "uyuni_no_server.bad.yml",
+		errMsg:   "Uyuni SD configuration requires server host",
+	},
 }
 
 func TestBadConfigs(t *testing.T) {

config/testdata/uyuni_no_server.bad.yml

@@ -0,0 +1,4 @@
+scrape_configs:
+  - job_name: uyuni
+    uyuni_sd_configs:
+      - server:

discovery/uyuni/uyuni.go

@@ -62,7 +62,7 @@ func init() {
 
 // SDConfig is the configuration for Uyuni based service discovery.
 type SDConfig struct {
-	Server           config.URL              `yaml:"server"`
+	Server           string                  `yaml:"server"`
 	Username         string                  `yaml:"username"`
 	Password         config.Secret           `yaml:"password"`
 	HTTPClientConfig config.HTTPClientConfig `yaml:",inline"`
@@ -122,11 +122,11 @@ func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	if err != nil {
 		return err
 	}
-	if c.Server.URL == nil {
+	if c.Server == "" {
 		return errors.New("Uyuni SD configuration requires server host")
 	}
 
-	_, err = url.Parse(c.Server.String())
+	_, err = url.Parse(c.Server)
 	if err != nil {
 		return errors.Wrap(err, "Uyuni Server URL is not valid")
 	}
@@ -199,8 +199,10 @@ func getEndpointInfoForSystems(
 
 // NewDiscovery returns a uyuni discovery for the given configuration.
 func NewDiscovery(conf *SDConfig, logger log.Logger) (*Discovery, error) {
-	var apiURL *url.URL
-	*apiURL = *conf.Server.URL
+	apiURL, err := url.Parse(conf.Server)
+	if err != nil {
+		return nil, err
+	}
 	apiURL.Path = path.Join(apiURL.Path, uyuniXMLRPCAPIPath)
 
 	rt, err := config.NewRoundTripperFromConfig(conf.HTTPClientConfig, "uyuni_sd")

discovery/uyuni/uyuni_test.go

@@ -0,0 +1,58 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package uyuni
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus/prometheus/discovery/targetgroup"
+)
+
+func testUpdateServices(respHandler http.HandlerFunc) ([]*targetgroup.Group, error) {
+	// Create a test server with mock HTTP handler.
+	ts := httptest.NewServer(respHandler)
+	defer ts.Close()
+
+	conf := SDConfig{
+		Server: ts.URL,
+	}
+
+	md, err := NewDiscovery(&conf, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return md.refresh(context.Background())
+}
+
+func TestUyuniSDHandleError(t *testing.T) {
+	var (
+		errTesting  = "unable to login to Uyuni API: request error: bad status code - 500"
+		respHandler = func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Header().Set("Content-Type", "application/xml")
+			io.WriteString(w, ``)
+		}
+	)
+	tgs, err := testUpdateServices(respHandler)
+
+	require.EqualError(t, err, errTesting)
+	require.Equal(t, len(tgs), 0)
+}