feat(tasks): implement atomic claims and leases

backend-api/internal/config/config.go

@@ -15,10 +15,16 @@ const (
 	AssetDirectoryEnvironment = "CMROUBAO_ASSET_DIR"
 	TLSCertificateEnvironment = "CMROUBAO_TLS_CERT_FILE"
 	TLSPrivateKeyEnvironment  = "CMROUBAO_TLS_KEY_FILE"
+	ClaimLeaseEnvironment     = "CMROUBAO_CLAIM_LEASE"
+	RunningLeaseEnvironment   = "CMROUBAO_RUNNING_LEASE"
+	ReadinessTTLEnvironment   = "CMROUBAO_READINESS_TTL"
 
 	defaultHTTPAddress    = "127.0.0.1:8080"
 	defaultDatabasePath   = "var/cmroubao.db"
 	defaultAssetDirectory = "var/assets"
+	defaultClaimLease     = 10 * time.Minute
+	defaultRunningLease   = 90 * time.Second
+	defaultReadinessTTL   = 2 * time.Minute
 )
 
 type LookupEnvironment func(string) (string, bool)
@@ -35,6 +41,9 @@ type Config struct {
 	IdleTimeout       time.Duration
 	ShutdownTimeout   time.Duration
 	MaxHeaderBytes    int
+	ClaimLease        time.Duration
+	RunningLease      time.Duration
+	ReadinessTTL      time.Duration
 }
 
 func Load(lookup LookupEnvironment) (Config, error) {
@@ -98,6 +107,36 @@ func Load(lookup LookupEnvironment) (Config, error) {
 				" must use loopback unless TLS is configured",
 		)
 	}
+	claimLease, err := durationEnvironment(
+		lookup,
+		ClaimLeaseEnvironment,
+		defaultClaimLease,
+		time.Minute,
+		30*time.Minute,
+	)
+	if err != nil {
+		return Config{}, err
+	}
+	runningLease, err := durationEnvironment(
+		lookup,
+		RunningLeaseEnvironment,
+		defaultRunningLease,
+		30*time.Second,
+		10*time.Minute,
+	)
+	if err != nil {
+		return Config{}, err
+	}
+	readinessTTL, err := durationEnvironment(
+		lookup,
+		ReadinessTTLEnvironment,
+		defaultReadinessTTL,
+		30*time.Second,
+		10*time.Minute,
+	)
+	if err != nil {
+		return Config{}, err
+	}
 
 	return Config{
 		HTTPAddress:       httpAddress,
@@ -111,9 +150,34 @@ func Load(lookup LookupEnvironment) (Config, error) {
 		IdleTimeout:       60 * time.Second,
 		ShutdownTimeout:   10 * time.Second,
 		MaxHeaderBytes:    1 << 20,
+		ClaimLease:        claimLease,
+		RunningLease:      runningLease,
+		ReadinessTTL:      readinessTTL,
 	}, nil
 }
 
+func durationEnvironment(
+	lookup LookupEnvironment,
+	name string,
+	defaultValue time.Duration,
+	minimum time.Duration,
+	maximum time.Duration,
+) (time.Duration, error) {
+	value, exists := lookup(name)
+	if !exists {
+		return defaultValue, nil
+	}
+	value = strings.TrimSpace(value)
+	duration, err := time.ParseDuration(value)
+	if err != nil || duration < minimum || duration > maximum {
+		return 0, errors.New(
+			name + " must be a duration between " +
+				minimum.String() + " and " + maximum.String(),
+		)
+	}
+	return duration, nil
+}
+
 func cleanOptionalPath(value string) string {
 	if value == "" {
 		return ""