def update_health_monitor(self, old_health_monitor,
                              health_monitor, service):
        """Update pool health monitor."""
        LOG.debug("Updating health monitor")
        target_pool = service["pools"][0]
        target_pool["provisioning_status"] = "PENDING_UPDATE"
        self._common_service_handler(service)
        return self._update_target(service,
                                   self._update_health_monitor_status,
                                   service["healthmonitors"])