[cmd/opampsupervisor] feat: Support environment variable expansion in supervisor config

.chloggen/opamp_supervisor_env_vars.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# 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. filelogreceiver)
+component: cmd/opampsupervisor
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Support environment variable expansion in the OpAMP supervisor config.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36269]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

cmd/opampsupervisor/go.mod

@@ -14,6 +14,9 @@ require (
 	github.com/stretchr/testify v1.9.0
 	go.opentelemetry.io/collector/config/configopaque v1.19.0
 	go.opentelemetry.io/collector/config/configtls v1.19.0
+	go.opentelemetry.io/collector/confmap v1.19.0
+	go.opentelemetry.io/collector/confmap/provider/envprovider v1.19.0
+	go.opentelemetry.io/collector/confmap/provider/fileprovider v1.19.0
 	go.opentelemetry.io/collector/semconv v0.113.0
 	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.0
@@ -25,9 +28,10 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/fsnotify/fsnotify v1.8.0 // indirect
-	github.com/go-viper/mapstructure/v2 v2.0.0-alpha.1 // indirect
+	github.com/go-viper/mapstructure/v2 v2.2.1 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/gorilla/websocket v1.5.1 // indirect
+	github.com/knadh/koanf/providers/confmap v0.1.0 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect

cmd/opampsupervisor/supervisor/config/config.go

@@ -4,6 +4,7 @@
 package config
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net/http"
@@ -13,18 +14,18 @@ import (
 	"runtime"
 	"time"
 
-	"github.com/knadh/koanf/parsers/yaml"
-	"github.com/knadh/koanf/providers/file"
-	"github.com/knadh/koanf/v2"
 	"github.com/open-telemetry/opamp-go/protobufs"
 	"go.opentelemetry.io/collector/config/configtls"
+	"go.opentelemetry.io/collector/confmap"
+	"go.opentelemetry.io/collector/confmap/provider/envprovider"
+	"go.opentelemetry.io/collector/confmap/provider/fileprovider"
 	"go.uber.org/zap/zapcore"
 )
 
 // Supervisor is the Supervisor config file format.
 type Supervisor struct {
-	Server       OpAMPServer
-	Agent        Agent
+	Server       OpAMPServer  `mapstructure:"server"`
+	Agent        Agent        `mapstructure:"agent"`
 	Capabilities Capabilities `mapstructure:"capabilities"`
 	Storage      Storage      `mapstructure:"storage"`
 	Telemetry    Telemetry    `mapstructure:"telemetry"`
@@ -36,18 +37,29 @@ func Load(configFile string) (Supervisor, error) {
 		return Supervisor{}, errors.New("path to config file cannot be empty")
 	}
 
-	k := koanf.New("::")
-	if err := k.Load(file.Provider(configFile), yaml.Parser()); err != nil {
+	resolverSettings := confmap.ResolverSettings{
+		URIs: []string{configFile},
+		ProviderFactories: []confmap.ProviderFactory{
+			fileprovider.NewFactory(),
+			envprovider.NewFactory(),
+		},
+		ConverterFactories: []confmap.ConverterFactory{},
+		DefaultScheme:      "env",
+	}
+
+	resolver, err := confmap.NewResolver(resolverSettings)
+	if err != nil {
 		return Supervisor{}, err
 	}
 
-	decodeConf := koanf.UnmarshalConf{
-		Tag: "mapstructure",
+	conf, err := resolver.Resolve(context.Background())
+	if err != nil {
+		return Supervisor{}, err
 	}
 
 	cfg := DefaultSupervisor()
-	if err := k.UnmarshalWithConf("", &cfg, decodeConf); err != nil {
-		return Supervisor{}, fmt.Errorf("cannot parse %s: %w", configFile, err)
+	if err = conf.Unmarshal(&cfg); err != nil {
+		return Supervisor{}, err
 	}
 
 	if err := cfg.Validate(); err != nil {
@@ -120,8 +132,8 @@ func (c Capabilities) SupportedCapabilities() protobufs.AgentCapabilities {
 }
 
 type OpAMPServer struct {
-	Endpoint   string
-	Headers    http.Header
+	Endpoint   string                 `mapstructure:"endpoint"`
+	Headers    http.Header            `mapstructure:"headers"`
 	TLSSetting configtls.ClientConfig `mapstructure:"tls,omitempty"`
 }
 
@@ -150,7 +162,7 @@ func (o OpAMPServer) Validate() error {
 }
 
 type Agent struct {
-	Executable              string
+	Executable              string           `mapstructure:"executable"`
 	OrphanDetectionInterval time.Duration    `mapstructure:"orphan_detection_interval"`
 	Description             AgentDescription `mapstructure:"description"`
 	ConfigApplyTimeout      time.Duration    `mapstructure:"config_apply_timeout"`