retry

type Backoff interface {
	// RetryAfter should return the time duration which should be
	// elapsed before the next queueForRetry.
	RetryAfter(attempts int) time.Duration
}

type DelayQueue interface {
	// Enqueue must save the message with priority based on the timestamp set.
	// If no timestamp is set, current timestamp should be assumed.
	Enqueue(item Item) error

	// Dequeue should read one message that has an expired timestamp and call
	// readFn with it. Success/failure from readFn must be considered as ACK
	// or nACK respectively. When message is not available, Dequeue should not
	// block but return ErrNoMessage. queue can return EOF to indicate that the
	// queue is fully drained. Other errors from the queue will be logged and
	// ignored.
	Dequeue(ctx context.Context, readFn ReadFn) error
}

type InMemQ struct {
	// contains filtered or unexported fields
}

type Item struct {
	Message     fusion.Msg `json:"message"`
	Attempts    int        `json:"attempts"`
	NextAttempt time.Time  `json:"next_attempt"`
	LastAttempt time.Time  `json:"last_attempt"`
}

type ReadFn func(ctx context.Context, item Item) error

type Retrier struct {
	// Proc is the fusion Proc that must be executed for each message.
	// This field must be set.
	Proc fusion.Proc

	// Queue can be set to use a delay queue. If not set, an in-memory
	// queue will be used.
	Queue DelayQueue

	// Backoff can be set to configure a backoff strategy to be used
	// during retries. If not set, constant backoff strategy will be
	// used with 1s intervals.
	Backoff Backoff

	// MaxRetries can be set to control how many retries should be done
	// before returning Fail status. Defaults to 3.
	MaxRetries int

	// EnqueueWorkers is the number of worker threads to use for moving
	// messages from stream to the queue.
	EnqueueWorkers int

	// ProcWorkers is the number of main worker threads to use for running
	// proc.
	ProcWorkers int

	// OnFailure is called when a message fails and exhausts all retries.
	// If not set, such messages will be logged and discarded.
	OnFailure func(item Item)

	// Log can be set to customise logging mechanism used by retrier. If
	// not set, logging will be disabled.
	Log fusion.Log
}