private <T> void addToFail(final Holder t) {
        Holder oldObj = concurrentHashMap.get(t.getKey());
        if (Objects.nonNull(oldObj)) {
            return;
        }
        FailureRegistryTask registryTask = new FailureRegistryTask(t.getKey(), this);
        concurrentHashMap.put(t.getKey(), t);
        timer.add(registryTask);
        logger.warn("Add to failback and wait for execution, {}", t.getPath());
    }
Add failure ApiDoc data register.

@param <T> the type parameter
@param t   the t
shenyu-register-center/shenyu-register-client/shenyu-register-client-api/src/main/java/org/apache/shenyu/register/client/api/FailbackRegistryRepository.java