t8y2/dbx · error

encode subscription group config: %w

Error message

encode subscription group config: %w

What it means

writeSubscriptionGroupConfig marshals the subscriptionGroupConfig struct to build the UPDATE_AND_CREATE_SUBSCRIPTION_GROUP command body. If json.Marshal fails it wraps the error as "encode subscription group config". This is a client-side serialization problem: the config struct contains a value json cannot encode (e.g. an unsupported type like a channel or func, or an invalid value such as a NaN float).

Source

Thrown at agents/drivers/rocketmq/consumers.go:626

func fetchSubscriptionGroupConfigs(ctx context.Context, address string) (map[string]*subscriptionGroupConfig, error) {
	response, err := invokeRemotingWithClient(ctx, address,
		remoting.NewRequest(remoting.GetAllSubscriptionGroupConfig, nil))
	if err != nil {
		return nil, err
	}
	var wrapper struct {
		SubscriptionGroupTable map[string]*subscriptionGroupConfig `json:"subscriptionGroupTable"`
	}
	if err := json.Unmarshal(repairRocketMQJSON(response.Body), &wrapper); err != nil {
		return nil, fmt.Errorf("decode subscription groups: %w", err)
	}
	return wrapper.SubscriptionGroupTable, nil
}

func writeSubscriptionGroupConfig(ctx context.Context, address string, config *subscriptionGroupConfig) error {
	body, err := json.Marshal(config)
	if err != nil {
		return fmt.Errorf("encode subscription group config: %w", err)
	}
	command := remoting.NewRequest(remoting.UpdateAndCreateSubscriptionGroup, nil)
	command.Body = body
	_, err = invokeRemotingWithClient(ctx, address, command)
	return err
}

func ensureMutationCoverage(action, resource string, attempted, succeeded int, lastErr error) error {
	if attempted <= 0 {
		return fmt.Errorf("no RocketMQ master brokers available to %s %s", action, resource)
	}
	if succeeded == attempted {
		return nil
	}
	message := fmt.Sprintf("failed to %s %s on all masters: %d of %d succeeded", action, resource, succeeded, attempted)
	if lastErr != nil {
		return fmt.Errorf("%s: %w", message, lastErr)
	}

View on GitHub (pinned to c0390bff16)

Solutions

1. Inspect the wrapped %w cause to find which field failed to marshal
2. Check recent additions to subscriptionGroupConfig for custom MarshalJSON implementations or unsupported types
3. Validate numeric fields for NaN/Inf before calling the write API
4. Add json tags to any newly added struct fields so they encode as plain JSON
5. Test the config with json.Marshal(config) in isolation before invoking the broker command

Example fix

// before
if err := json.Marshal(config); err != nil { /* fails on custom type */ }
// after
type subscriptionGroupConfig struct {
    GroupName    string  `json:"groupName"`
    ConsumeTimeoutMinutes float64 `json:"consumeTimeoutMin"` // plain field, custom MarshalJSON removed
}

if _, err := json.Marshal(config); err != nil {
    return fmt.Errorf("subscription group config not serializable: %w", err)
}

if err := writeSubscriptionGroupConfig(ctx, address, cfg); err != nil {
    var encErr *json.UnsupportedTypeError
    if errors.As(err, &encErr) {
        log.Printf("unsupported field type in config: %v", encErr.Value)
    }
    return err
}

When it happens

Trigger: Calling alterSubscriptionGroupConfig with a subscriptionGroupConfig populated with values that json.Marshal cannot serialize — practically rare since the struct fields are basic types; most likely when a custom field type with a broken MarshalJSON returning an error was added.

Common situations: A developer extends subscriptionGroupConfig with a field of a type whose MarshalJSON method errors, or passes a config built programmatically containing an invalid float (NaN/Inf).

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• decode ACL list: %w
• decode consumer status: %w
• decode consumer stats: %w
• decode subscription groups: %w
• invalid params: %w

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/11017f2892e189e0. Report an issue: GitHub.