Error Classification

The invoker chain classifies errors to drive execution behavior. This classification determines whether an error is retried, sent to DLQ, or silently handled.

Error Types

RetryableError

Explicitly marks an error as retryable:

return invoker.RetryableError{Err: errors.New("connection timeout")}

PermanentError

Marks an error as terminal (never retried, sent to DLQ):

return invoker.PermanentError{Err: errors.New("invalid data")}

Retryable Interface

type Retryable interface {
    Retryable() bool
}

Terminal Interface

type Terminal interface {
    Terminal() bool
}

Sentinel Errors

Error	Description
ErrDuplicate	Idempotency check failed (already processed)
ErrRateLimited	Rate limit exceeded
ErrCircuitOpen	Circuit breaker is open
ErrSendToDLQ	Internal: signals retry exhaustion for terminal errors

Classification Table

Error Type	Retried?	DLQ?	Circuit Breaker?
Default (unknown)	Yes	After exhaustion	Yes
RetryableError	Yes	After exhaustion	Yes
PermanentError	No	Yes	No
Terminal interface	No	Yes	No
Retryable interface	Depends on return	After exhaustion	Yes
ErrDuplicate	No	No	No
ErrRateLimited	No	No	No
ErrCircuitOpen	No	No	N/A
context.Canceled	No	No	No
context.DeadlineExceeded	No	No	No
ErrSendToDLQ	No	N/A	No

Custom Error Types

You can create domain-specific error types:

type ValidationError struct {
    Field   string
    Message string
}

func (e ValidationError) Error() string {
    return fmt.Sprintf("validation: %s - %s", e.Field, e.Message)
}

func (e ValidationError) Terminal() bool { return true }

type NetworkError struct {
    Err error
}

func (e NetworkError) Error() string   { return e.Err.Error() }
func (e NetworkError) Unwrap() error   { return e.Err }
func (e NetworkError) Retryable() bool { return true }