Allow to override rancher provider settings

Currently it is only possible to set provider settings over yaml file.

This commit introduces env variables to override URL, token and cluster name.

If particular environment variable is set it overrides value supplied in yaml file.

Signed-off-by: Dinar Valeev <k0da@opensuse.org>
Co-authored-by: Donovan Muller <donovan.muller@absa.africa>

Author: k0da

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")
+	}
+}