Allow to override rancher provider settings

cluster-autoscaler/cloudprovider/rancher/README.md

@@ -10,6 +10,12 @@ The `cluster-autoscaler` for Rancher needs a configuration file to work by
 using `--cloud-config` parameter. An up-to-date example can be found in
 [examples/config.yaml](./examples/config.yaml).
 
+### Configuration via environment variables
+In order to override URL, token or clustername use following environment variables:
+ - RANCHER_URL
+ - RANCHER_TOKEN
+ - RANCHER_CLUSTER_NAME
+
 ### Permissions
 
 The Rancher server account provided in the `cloud-config` requires the

cluster-autoscaler/cloudprovider/rancher/rancher_config.go

@@ -23,6 +23,12 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
+const (
+	envUrl          = "RANCHER_URL"
+	envClusterName  = "RANCHER_CLUSTER_NAME"
+	envClusterToken = "RANCHER_TOKEN"
+)
+
 type cloudConfig struct {
 	URL               string `yaml:"url"`
 	Token             string `yaml:"token"`
@@ -31,6 +37,22 @@ type cloudConfig struct {
 	ClusterAPIVersion string `yaml:"clusterAPIVersion"`
 }
 
+func overrideFromEnv(c *cloudConfig) *cloudConfig {
+	url := os.Getenv(envUrl)
+	cName := os.Getenv(envClusterName)
+	token := os.Getenv(envClusterToken)
+	if url != "" {
+		c.URL = url
+	}
+	if cName != "" {
+		c.ClusterName = cName
+	}
+	if token != "" {
+		c.Token = token
+	}
+	return c
+}
+
 func newConfig(file string) (*cloudConfig, error) {
 	b, err := os.ReadFile(file)
 	if err != nil {
@@ -42,5 +64,7 @@ func newConfig(file string) (*cloudConfig, error) {
 		return nil, fmt.Errorf("unable to unmarshal config file: %w", err)
 	}
 
+	config = overrideFromEnv(config)
+
 	return config, nil
 }

cluster-autoscaler/cloudprovider/rancher/rancher_config_test.go

@@ -16,7 +16,10 @@ limitations under the License.
 
 package rancher
 
-import "testing"
+import (
+	"os"
+	"testing"
+)
 
 func TestNewConfig(t *testing.T) {
 	cfg, err := newConfig("./examples/config.yaml")
@@ -40,3 +43,25 @@ func TestNewConfig(t *testing.T) {
 		t.Fatal("expected cluster namespace to be set")
 	}
 }
+
+func TestEnvOverride(t *testing.T) {
+	expectedUrl := "http://rancher-site.com"
+	overrideToken := "token:changed"
+	overrideClusterName := "cluster-changed"
+	os.Setenv(envUrl, expectedUrl)
+	os.Setenv(envClusterToken, overrideToken)
+	os.Setenv(envClusterName, overrideClusterName)
+	cfg, err := newConfig("./examples/config.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.URL != expectedUrl {
+		t.Fatal("expected url to be set")
+	}
+	if cfg.Token != overrideToken {
+		t.Fatal("expected token to be set")
+	}
+	if cfg.ClusterName != overrideClusterName {
+		t.Fatal("expected cluster name to be set")
+	}
+}