Documentation
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Overview ¶
Package idempotency adds optional, dependency-free dedupe to a babelqueue consumer: it wraps a babelqueue.Handler so a message whose meta.id was already processed is skipped instead of run again (ADR-0022). It is the Go mirror of the PHP BabelQueue\Idempotency helper.
It lives in the core module (zero dependencies, stdlib only) rather than a transport submodule, so it ships with every consumer.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Wrap ¶
func Wrap(store Store, handler babelqueue.Handler) babelqueue.Handler
Wrap returns handler decorated so a message whose meta.id was already processed successfully is skipped. It composes with the App's ack-on-return / retry-on-error contract:
- an already-seen id → returns nil, so the runtime acks it and the broker stops redelivering;
- the handler returns an error → the id is left unmarked and the error propagates, so retry / dead-letter still apply and a later delivery runs the handler again;
- a message with no usable meta.id runs unchanged (fail-open).
Register it like any handler: app.Handle(urn, idempotency.Wrap(store, handler)).
Types ¶
type InMemoryStore ¶
type InMemoryStore struct {
// contains filtered or unexported fields
}
InMemoryStore is a process-local, goroutine-safe Store backed by a map. It is suitable for tests and single-process consumers; it is not shared across workers and not persistent — use a Redis- or database-backed store for production fleets.
func NewInMemoryStore ¶
func NewInMemoryStore() *InMemoryStore
NewInMemoryStore returns an empty in-memory store.
func (*InMemoryStore) Forget ¶
func (s *InMemoryStore) Forget(_ context.Context, messageID string) error
Forget implements Store.
type Store ¶
type Store interface {
// Seen reports whether this message id has already been processed (remembered).
Seen(ctx context.Context, messageID string) (bool, error)
// Remember records this message id as processed.
Remember(ctx context.Context, messageID string) error
// Forget drops a message id from the store (manual eviction; a backend may also
// expire ids on its own TTL).
Forget(ctx context.Context, messageID string) error
}
Store is a pluggable record of message ids that have already been processed, keyed on the envelope's meta.id (the canonical per-message identity). The reference InMemoryStore is for tests / single-process consumers; production backends (Redis, a database table) implement the same three methods.
The contract is "seen-set" dedupe: it answers "was this id processed?", not "what did it return" — queue handlers have no response to replay. It provides post-success dedupe under at-least-once + idempotent handlers (error-handling.md §1), not exactly-once and not in-flight concurrency locking. A transactional / outbox mode is a documented future direction (ADR-0022).
Source Files