nexora-retry

Retry policies for capability executions. The RetryInterceptor consults the policy registry before each re-attempt.

RetryPolicy interface

public interface RetryPolicy {
    boolean shouldRetry(int attemptsMade, Throwable cause);
    Duration backoffDelay(int attemptsMade);
}

Two built-in implementations:

Class	Behaviour
NoRetryPolicy	Never retries. Default when no policy is configured.
ExponentialBackoffPolicy	Exponential delay with ±25% jitter.

---

ExponentialBackoffPolicy

RetryPolicy policy = ExponentialBackoffPolicy.builder()
    .maxAttempts(4)
    .initialDelay(Duration.ofMillis(100))
    .multiplier(2.0)
    .maxDelay(Duration.ofSeconds(8))
    .retryOn(IOException.class, TimeoutException.class)
    .build();

Parameter	Default	Description
maxAttempts	3	Total attempts including the first call
initialDelay	200 ms	Delay before attempt 2
multiplier	2.0	Multiplied each retry (must be > 1.0)
maxDelay	10 s	Upper bound on delay between retries
retryOn	all exceptions	Restrict retries to specific exception types

The ±25% jitter prevents retry storms when many concurrent executions fail simultaneously.

---

RetryPolicyRegistry

Maps named policy IDs to RetryPolicy instances. Referenced by StepDefinition.retryPolicyId.

NexoraEngine engine = NexoraEngine.builder()
    .withDefaultRetryPolicy(
        ExponentialBackoffPolicy.builder()
            .maxAttempts(3)
            .initialDelay(Duration.ofMillis(200))
            .build()
    )
    .build();

The default retry policy applies to any step that does not declare a retryPolicyId. To disable retries globally, pass RetryPolicy.noRetry().

---

Per-step retry policies

Override retry behaviour on a per-step basis via StepDefinition:

new StepDefinition(
    "charge",
    "charge_card",
    goal -> goal.contains("order"),
    inputs,
    "chargeResult",
    Set.of("validate"),
    "payment-retry-policy",   // matches a named policy in the registry
    Duration.ofSeconds(5)     // per-step timeout
)