feat(agent): UPDATE_TIMEOUT and DOCKER_CONFIG settings (#7)

internal/agent/config/config.go

@@ -2,10 +2,14 @@
 package config
 
 import (
+	"encoding/json"
 	"errors"
+	"fmt"
 	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
+	"time"
 )
 
 var masterKeyPattern = regexp.MustCompile(`^sha256:[0-9a-f]{64}$`)
@@ -17,8 +21,17 @@ type Config struct {
 	Token     string // AGENT_TOKEN, shown once when the agent was added
 	SelfID    string // SELF_ID, defaults to the hostname (= container ID prefix)
 	LogLevel  string // LOG_LEVEL, default info
+
+	// UpdateTimeout bounds one update job (UPDATE_TIMEOUT, default 5m).
+	UpdateTimeout time.Duration
+	// DockerConfig is the directory holding config.json with registry
+	// credentials (DOCKER_CONFIG). Empty means anonymous registry access.
+	DockerConfig string
 }
 
+// defaultUpdateTimeout is used when UPDATE_TIMEOUT is unset.
+const defaultUpdateTimeout = 5 * time.Minute
+
 // Load reads and validates the agent configuration. It fails fast so a
 // misconfigured agent never starts dialling.
 func Load() (*Config, error) {
@@ -28,6 +41,9 @@ func Load() (*Config, error) {
 		Token:     os.Getenv("AGENT_TOKEN"),
 		SelfID:    os.Getenv("SELF_ID"),
 		LogLevel:  os.Getenv("LOG_LEVEL"),
+
+		UpdateTimeout: defaultUpdateTimeout,
+		DockerConfig:  os.Getenv("DOCKER_CONFIG"),
 	}
 	switch {
 	case cfg.MasterURL == "":
@@ -41,6 +57,18 @@ func Load() (*Config, error) {
 	case cfg.Token == "":
 		return nil, errors.New("AGENT_TOKEN is required")
 	}
+	if v := os.Getenv("UPDATE_TIMEOUT"); v != "" {
+		d, err := time.ParseDuration(v)
+		if err != nil || d <= 0 {
+			return nil, fmt.Errorf("UPDATE_TIMEOUT must be a positive duration such as 5m, got %q", v)
+		}
+		cfg.UpdateTimeout = d
+	}
+	if cfg.DockerConfig != "" {
+		if err := checkDockerConfig(cfg.DockerConfig); err != nil {
+			return nil, err
+		}
+	}
 	if cfg.SelfID == "" {
 		cfg.SelfID, _ = os.Hostname()
 	}
@@ -49,3 +77,17 @@ func Load() (*Config, error) {
 	}
 	return cfg, nil
 }
+
+// checkDockerConfig fails when DOCKER_CONFIG is set but its config.json is
+// missing or not JSON, so a typo does not silently turn into anonymous pulls.
+func checkDockerConfig(dir string) error {
+	path := filepath.Join(dir, "config.json")
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Errorf("DOCKER_CONFIG: read %s: %w", path, err)
+	}
+	if !json.Valid(raw) {
+		return fmt.Errorf("DOCKER_CONFIG: %s is not valid JSON", path)
+	}
+	return nil
+}