roachprod: use yaml for creating the cluster config

currently a template is used to generate the yaml for the
prometheus cluster config. this is error-prone and adding new
parameters also becomes risky.
with this change, we are using go yaml to generate the yaml

Fixes: cockroachdb#124320
Epic: none

pkg/roachprod/promhelperclient/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
         "//pkg/util/httputil",
         "@com_github_cockroachdb_errors//:errors",
         "@com_google_cloud_go_storage//:storage",
+        "@in_gopkg_yaml_v2//:yaml_v2",
         "@org_golang_google_api//idtoken",
         "@org_golang_google_api//option",
         "@org_golang_x_oauth2//:oauth2",
@@ -26,6 +27,7 @@ go_test(
     deps = [
         "//pkg/roachprod/logger",
         "@com_github_stretchr_testify//require",
+        "@in_gopkg_yaml_v2//:yaml_v2",
         "@org_golang_google_api//idtoken",
         "@org_golang_x_oauth2//:oauth2",
     ],

pkg/roachprod/promhelperclient/client.go

@@ -23,13 +23,13 @@ import (
 	"os"
 	"strconv"
 	"strings"
-	"text/template"
 
 	"github.com/cockroachdb/cockroach/pkg/roachprod/logger"
 	"github.com/cockroachdb/cockroach/pkg/util/httputil"
 	"github.com/cockroachdb/errors"
 	"golang.org/x/oauth2"
 	"google.golang.org/api/idtoken"
+	"gopkg.in/yaml.v2"
 )
 
 const (
@@ -150,38 +150,29 @@ func getUrl(promUrl, clusterName string) string {
 	return fmt.Sprintf("%s/%s/%s/%s", promUrl, resourceVersion, resourceName, clusterName)
 }
 
-// ccParams are the params for the clusterConfFileTemplate
-type ccParams struct {
-	Targets []string
-	Labels  []string
+// CCParams are the params for the cluster configs
+type CCParams struct {
+	Targets []string          `yaml:"targets"`
+	Labels  map[string]string `yaml:"labels"`
 }
 
-const clusterConfFileTemplate = `- targets:
-{{range $val := .Targets}}  - {{$val}}
-{{end}}  labels:
-{{range $val := .Labels}}    {{$val}}
-{{end}}
-`
-
 // createClusterConfigFile creates the cluster config file per node
 func buildCreateRequest(nodes map[int]string, insecure bool) (io.Reader, error) {
-	buffer := bytes.NewBufferString("---\n")
+	configs := make([]*CCParams, 0)
 	for i, n := range nodes {
-		params := &ccParams{
+		params := &CCParams{
 			Targets: []string{n},
-			Labels:  make([]string, 0),
-		}
-		params.Labels = append(params.Labels,
-			fmt.Sprintf("node: \"%s\"", strconv.Itoa(i)),
-			"tenant: system",
-		)
-		t := template.Must(template.New("start").Parse(clusterConfFileTemplate))
-		if err := t.Execute(buffer, params); err != nil {
-			return nil, err
+			Labels:  make(map[string]string, 0),
 		}
+		params.Labels["node"] = strconv.Itoa(i)
+		params.Labels["tenant"] = "system"
+		configs = append(configs, params)
 	}
-
-	b, err := json.Marshal(&instanceConfigRequest{Config: buffer.String(), Insecure: insecure})
+	cb, err := yaml.Marshal(&configs)
+	if err != nil {
+		return nil, err
+	}
+	b, err := json.Marshal(&instanceConfigRequest{Config: string(cb), Insecure: insecure})
 	if err != nil {
 		return nil, err
 	}

pkg/roachprod/promhelperclient/client_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"golang.org/x/oauth2"
 	"google.golang.org/api/idtoken"
+	"gopkg.in/yaml.v2"
 )
 
 func TestUpdatePrometheusTargets(t *testing.T) {
@@ -57,8 +58,19 @@ func TestUpdatePrometheusTargets(t *testing.T) {
 			require.Equal(t, getUrl(promUrl, "c1"), url)
 			ir, err := getInstanceConfigRequest(io.NopCloser(body))
 			require.Nil(t, err)
-			// TODO (bhaskar): check for the correct yaml
 			require.NotNil(t, ir.Config)
+			configs := make([]*CCParams, 0)
+			require.Nil(t, yaml.UnmarshalStrict([]byte(ir.Config), &configs))
+			require.Equal(t, 2, len(configs))
+			for _, c := range configs {
+				if c.Labels["node"] == "1" {
+					require.Equal(t, "n1", c.Targets[0])
+				} else {
+					require.Equal(t, "n3", c.Targets[0])
+					require.Equal(t, "3", c.Labels["node"])
+				}
+				c.Labels["tenant"] = "system"
+			}
 			return &http.Response{
 				StatusCode: 200,
 			}, nil