def _update_cache_settings(self, memcached_nodes):
        logger.info("Updating CACHE_BACKEND settings")
        assert len(memcached_nodes) > 0
        if memcached_nodes:
            memcached_port = 11211
            cache_str = 'memcached://'
            cache_instances = []
            for node in memcached_nodes:
                cache_instances.append(
                    "%s:%s" % (
                        node.boto_instance.private_dns_name,
                        memcached_port,
                    )
                )
            cache_str += ';'.join(cache_instances)
            env.pstat_settings['CACHE_BACKEND'] = cache_str
Update the pstat_settings['CACHE_BACKEND'] environment variable with
dataset/ETHPy150Open winhamwr/neckbeard/neckbeard/brain_wrinkles/pstat/app.py/AppServerProvisioner._update_cache_settings