function fanoutOnSubject($redis, $loginId, $feed)
{
//fan-out to followers
$key = Nest::followers("user", $loginId);
$followers = $redis->smembers($key);
foreach ($followers as $followerId) {
//push to follower's feeds
$key = Nest::feeds("user", $followerId);
$redis->lpush($key, $feed);
}
}
