static RetryRule onException(BiPredicate<? super ClientRequestContext, ? super Throwable> exceptionFilter,
                                 Backoff backoff) {
        return builder().onException(exceptionFilter).thenBackoff(backoff);
    }
Returns a newly created {@link RetryRule} that will retry with the specified {@link Backoff} if an
{@link Exception} is raised and the specified {@code exceptionFilter} returns {@code true}.
core/src/main/java/com/linecorp/armeria/client/retry/RetryRule.java