Set cluster_name var in logs vars separately and not in init (#2777)

If we set the `cluster_name` field in log variables (extran fields that are
printed in logs), inside the `init` function of `log` package, we would
un necessarily be calling k8s api even from the places where we don't have to
do anything with the k8s api.
To fix this, this commit introduces a new function that can be used to setup
that field in the logs vars and that function will only be called from the
places where we need the logs to have to the `cluster_name` field, for example
`kanctl`, `controller` and `repository-controller`.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

cmd/controller/main.go

@@ -17,8 +17,11 @@ package main
 
 import (
 	"github.com/kanisterio/kanister/pkg/kancontroller"
+	"github.com/kanisterio/kanister/pkg/log"
 )
 
 func main() {
+	log.SetupClusterNameInLogVars()
+
 	kancontroller.Execute()
 }

cmd/kanctl/main.go

@@ -17,6 +17,7 @@ package main
 
 import (
 	"github.com/kanisterio/kanister/pkg/kanctl"
+	"github.com/kanisterio/kanister/pkg/log"
 )
 
 func init() {
@@ -25,5 +26,7 @@ func init() {
 }
 
 func main() {
+	log.SetupClusterNameInLogVars()
+
 	kanctl.Execute()
 }

cmd/reposervercontroller/main.go

@@ -68,6 +68,8 @@ func main() {
 	flag.StringVar(&probeAddr, "health-probe-bind-address", ":8081", "The address the probe endpoint binds to.")
 	logLevel := getLogLevel()
 
+	log.SetupClusterNameInLogVars()
+
 	opts := zap.Options{
 		Level: logLevel,
 	}

pkg/log/log.go

@@ -93,7 +93,11 @@ func initEnvVarFields() {
 			envVarFields = field.Add(envVarFields, strings.ToLower(e), ev)
 		}
 	}
+}
 
+// SetupClusterNameInLogVars sets up the `cluster_name` field in `envVarFields`
+// so that it can be printed with the logs.
+func SetupClusterNameInLogVars() {
 	if clsName, err := config.GetClusterName(nil); err == nil {
 		envVarFields = field.Add(envVarFields, "cluster_name", clsName)
 	}