def _default_renewal_time(cert_pem: bytes) -> datetime.datetime:
…
    cert = x509.load_pem_x509_certificate(cert_pem)

    not_before = cert.not_valid_before_utc
    lifetime = cert.not_valid_after_utc - not_before
    if lifetime.total_seconds() < 10 * 86400:
        default_rt = not_before + lifetime / 2
    else:
        default_rt = not_before + lifetime * 2 / 3

    return default_rt

def should_autorenew(lineage: storage.RenewableCert,
                     ari_clients: AriClientPool) -> bool:
…
    if not lineage.autorenewal_is_enabled():
        return False

    cert = lineage.version("cert", lineage.latest_common_version())
    with open(cert, 'rb') as f:
        cert_pem = f.read()

    renewal_time = _ari_renewal_time(lineage, cert_pem, ari_clients)

    now = datetime.datetime.now(datetime.timezone.utc)

    if renewal_time and now > renewal_time:
        return True

    # Renewals on the basis of revocation
    if lineage.ocsp_revoked(lineage.latest_common_version()):
        logger.debug("Should renew, certificate is revoked.")
        return True

    # If the renew_before_expiry config field is set, check if it says we should renew
    config_interval = lineage.configuration.get("renew_before_expiry")
    if config_interval is not None:
        notAfter = crypto_util.notAfter(cert)
        if notAfter < storage.add_time_interval(now, config_interval):
            logger.debug("Should renew, less than %s before certificate "
                            "expiry %s.", config_interval,
                            notAfter.strftime("%Y-%m-%d %H:%M:%S %Z"))
            return True
    # Only use the default if we don't have an ARI or renew_before_expiry value
    elif renewal_time is None:
        default_renewal_time = _default_renewal_time(cert_pem)
        if now > default_renewal_time:
            return True

    return False
Warm-up
