t8y2/dbx · error

pattern is required

Error message

pattern is required

What it means

setPolicy requires a pattern string (the regex a queue/exchange name is matched against to apply the policy). The library throws this when the pattern param is absent or whitespace-only, because a policy without a match pattern can never apply to any resource.

Source

Thrown at agents/drivers/rabbitmq/operations.go:1055

		"pattern":    stringOrEmpty(policy, "pattern"),
		"applyTo":    stringOrEmpty(policy, "apply-to"),
		"priority":   longOrDefault(policy, "priority", 0),
		"definition": definition,
	}
}

func (s *server) setPolicy(params jsonObject) (any, error) {
	vhost, err := permissionVhost(params)
	if err != nil {
		return nil, err
	}
	name, err := policyName(params)
	if err != nil {
		return nil, err
	}
	pattern := stringOrEmpty(params, "pattern")
	if strings.TrimSpace(pattern) == "" {
		return nil, errors.New("pattern is required")
	}
	definition := objectOrNil(params, "definition")
	if definition == nil {
		return nil, errors.New("definition is required")
	}
	connection, err := s.requireConnectionConfig(params)
	if err != nil {
		return nil, err
	}
	body := jsonObject{
		"pattern":    pattern,
		"apply-to":   stringOrDefault(params, "applyTo", "queues"),
		"priority":   intOrDefault(params, "priority", 0),
		"definition": definition,
	}
	if _, err := managementSend(connection, http.MethodPut,
		"/api/policies/"+urlEncodeVhost(vhost)+"/"+urlEncodePathSegment(name), body); err != nil {
		return nil, err

View on GitHub (pinned to c0390bff16)

Solutions

1. Add a pattern regex, e.g. ".*" to match all queues
2. Provide a targeted pattern such as "^orders\\." for name-prefixed queues
3. Validate params include non-empty pattern before dispatch

Example fix

// before
{ "op": "setPolicy", "name": "ha", "definition": { "ha-mode": "all" } }
// after
{ "op": "setPolicy", "name": "ha", "pattern": ".*", "definition": { "ha-mode": "all" } }

if (typeof params.pattern !== "string" || !params.pattern.trim()) throw new Error("pattern is required");

function hasPattern(p) { return typeof p.pattern === "string" && p.pattern.trim().length > 0; }

try { await agent.dispatch("setPolicy", params); } catch (e) { if (/pattern is required/.test(e.message)) { params.pattern = ".*"; await agent.dispatch("setPolicy", params); } else throw e; }

When it happens

Trigger: Dispatching setPolicy with name and definition but no pattern, or pattern:"" / whitespace.

Common situations: Config-driven policy provisioning where the pattern field was omitted; YAML/JSON templating that dropped empty strings; misunderstanding pattern as optional like in some RabbitMQ UIs.

Understand the failure class

Background: Missing required parameter errors: what 'X is required' and 'the required X param is missing' mean, and how to fix them — this error's family across 27 libraries.

Related errors

• definition is required
• virtual_host is required
• all_vhosts is only supported for list operations
• user name is required
• Not connected. Call connect first.

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/e55e366c6747975d. Report an issue: GitHub.