Retry Invoker

The retry invoker handles transient failures with exponential backoff.

Configuration

invoker.NewRetry(invoker.RetryPolicy{
    MaxAttempts: 3,
    BaseDelay:   100 * time.Millisecond,
    MaxDelay:    5 * time.Second,
}, metrics)

RetryPolicy

Field	Type	Description
MaxAttempts	int	Maximum number of attempts (including first)
BaseDelay	time.Duration	Initial delay before first retry
MaxDelay	time.Duration	Maximum delay cap

Backoff Strategy

Exponential backoff: delay = 2^attempt * BaseDelay, capped at MaxDelay.

Attempt 1: immediate
Attempt 2: 100ms
Attempt 3: 200ms
Attempt 4: 400ms (capped at MaxDelay)

Error Classification

The retry invoker classifies errors to decide behavior:

// Explicitly retryable
return invoker.RetryableError{Err: err}

// Explicitly permanent (never retried, sent to DLQ)
return invoker.PermanentError{Err: err}

Classification Logic

1. ErrDuplicate, ErrRateLimited, ErrCircuitOpen → not retried, not terminal
2. context.Canceled, context.DeadlineExceeded → not retried
3. Implements Terminal interface with Terminal() == true → terminal, sent to DLQ
4. Implements Retryable interface → retried if Retryable() == true
5. Default (unknown errors) → retried

Metrics

Metric	Type	Description
eventbus_retry_attempt_total	Counter	Total retry attempts
eventbus_retry_success_total	Counter	Successes after retry
eventbus_retry_terminal_total	Counter	Terminal errors (to DLQ)
eventbus_retry_exhausted_total	Counter	All retries exhausted
eventbus_retry_backoff_ms	Histogram	Backoff delay duration