Opamp Bridge can read env variables on config generation (#2578)

* call os.expandenv in loadfromfile to substitute environment variable values in the yaml config

* add tests to confirm headers can be parsed from env variables

* undo this change i didnt intend

* rm dupe call

* add changelog

Author: jdcrouse

.chloggen/bridge-config-env-variables.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. operator, target allocator, github action)
+component: opamp bridge
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Added env variable parsing to opamp bridge config loading
+
+# One or more tracking issues related to the change
+issues: [2577]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

cmd/operator-opamp-bridge/config/config.go

@@ -269,7 +269,8 @@ func LoadFromFile(cfg *Config, configFile string) error {
 	if err != nil {
 		return err
 	}
-	if err = yaml.Unmarshal(yamlFile, cfg); err != nil {
+	envExpandedYaml := []byte(os.ExpandEnv(string(yamlFile)))
+	if err = yaml.Unmarshal(envExpandedYaml, cfg); err != nil {
 		return fmt.Errorf("error unmarshaling YAML: %w", err)
 	}
 	return nil

cmd/operator-opamp-bridge/config/config_test.go

@@ -16,6 +16,7 @@ package config
 
 import (
 	"fmt"
+	"os"
 	"testing"
 	"time"
 
@@ -25,7 +26,8 @@ import (
 
 func TestLoad(t *testing.T) {
 	type args struct {
-		file string
+		file         string
+		envVariables map[string]string
 	}
 	tests := []struct {
 		name    string
@@ -136,13 +138,19 @@ func TestLoad(t *testing.T) {
 			name: "base case with headers",
 			args: args{
 				file: "./testdata/agentwithheaders.yaml",
+				envVariables: map[string]string{
+					"MY_ENV_VAR_1": "my-env-variable-1-value",
+					"MY_ENV_VAR_2": "my-env-variable-2-value",
+				},
 			},
 			want: &Config{
 				RootLogger: logr.Discard(),
 				Endpoint:   "ws://127.0.0.1:4320/v1/opamp",
 				Headers: map[string]string{
-					"authentication": "access-12345-token",
-					"my-header-key":  "my-header-value",
+					"authentication":    "access-12345-token",
+					"my-header-key":     "my-header-value",
+					"my-env-variable-1": "my-env-variable-1-value",
+					"my-env-variable-2": "my-env-variable-2-value",
 				},
 				Capabilities: map[Capability]bool{
 					AcceptsRemoteConfig:            true,
@@ -164,6 +172,12 @@ func TestLoad(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			if tt.args.envVariables != nil {
+				for key, value := range tt.args.envVariables {
+					err := os.Setenv(key, value)
+					assert.NoError(t, err)
+				}
+			}
 			got := NewConfig(logr.Discard())
 			err := LoadFromFile(got, tt.args.file)
 			if !tt.wantErr(t, err, fmt.Sprintf("Load(%v)", tt.args.file)) {
@@ -173,7 +187,6 @@ func TestLoad(t *testing.T) {
 			got.ClusterConfig = tt.want.ClusterConfig
 			got.RootLogger = tt.want.RootLogger
 			assert.Equalf(t, tt.want, got, "Load(%v)", tt.args.file)
-
 		})
 	}
 }

cmd/operator-opamp-bridge/config/testdata/agentwithheaders.yaml

@@ -2,6 +2,8 @@ endpoint: ws://127.0.0.1:4320/v1/opamp
 headers:
   authentication: "access-12345-token"
   my-header-key: "my-header-value"
+  my-env-variable-1: "${MY_ENV_VAR_1}"
+  my-env-variable-2: "$MY_ENV_VAR_2"
 capabilities:
   AcceptsRemoteConfig: true
   ReportsEffectiveConfig: true