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> Once you move from storing session data in-memory on the webserver, and add a network call, I don't move from storing session data in-memory; I never store s
by irahul 14y ago
> Once you move from storing session data in-memory on the webserver, and add a network call,
I don't move from storing session data in-memory; I never store session data in-memory. Well, I do indirectly but that's always some distributed memory system. And there isn't necessarily a network call. A single webserver accessing memcache running on the same machine is as fast as accessing in-memory cache. When there is more than one memcache server, there has got to be a network call, but I am yet to see an application where that is an overhead. Compared to disk access, that is a floating point error.
> why not just store the data alongside the users other data in a fast datastore? That could be Redis, Cassandra, whatever.
What advantage would I have from storing the session alongside the user data? My datastore isn't Redis, Cassandra. It's postgresql. Redis is my cache/data structure server. The only nosql solution which I would consider for user data is mongo.
> This isn't babble -- it's honestly a pretty common technique.
Other than your insistence on using Redis, I don't see how your technique is any different from mine.
> If your site sees millions of users, storing a session for visitors that aren't logged in is prohibitive and unnecessary.
If the user aren't logged in and don't have any user data, there is no session to be loaded. When the user logs in, set the secure cookie with the session id. When a new request comes in, if the secure cookie has the session id, load it. For a not-logged in user, there is not session id and nothing is loaded.
> You can store UI customizations and basic memoization in a client-side cookie if you need to.
The only thing I will store in the cookie is session id. Cookie length constraints and network payload for every request is more overhead than loading the session on the server side.
> If you're building something small or basic, then you probably won't have multiple webservers and you can use fast in-memory sessions without concern. This only applies once you need to worry about scale.
For sessions, session id in cookie and memcache/redis as session store works for all scale.
- encoderer 14y agoIf you've got a single webserver then we're speaking a different language. That's not an insult or anything, it's just that I'm talking about techniques we use to support millions of pageviews a day. There is no one way to build a system of course. I'd love to hear more about your lessons-learned, but this really isn't a good forum for that. Though even at your scale you should consider redis as a drop-in replacement for memcache. It benchmarks faster in many cases, and has support for data structures (lists, sorted sets, etc) that make your life easier. And see my comment below clarifying what you said about cookies. > For sessions, session id in cookie and memcache/redis as session store works for all scale. Kind of a bold statement? GL with that.
- irahul 14y ago> If you've got a single webserver then we're speaking a different language. That's not an insult or anything, it's just that I'm talking about techniques we use to support millions of pageviews a day. And where did I talk about single webserver? You said "Once you move from storing session data in-memory on the webserver, and add a network call,", to which I said I never do in-memory session, even for a single webserver. Get over yourself - you aren't a special snowflake who deals with more than one more webserver. > Though even at your scale you should consider redis as a drop-in replacement for memcache. It benchmarks faster in many cases, and has support for data structures (lists, sorted sets, etc) that make your life easier. "Though even at your scale " As I said, get over yourself. All you have offered is somehow storing session in Redis makes you scale. How on earth would you know what scale I am talking about? I don't remember mentioning it. And I know what redis does. Cargo cult mentality viz. "redis is really better than memcached" are the main reason behind fucked up systems. > And see my comment below clarifying what you said about cookies. Yes, I saw your comment. Local storage is not the solution for coming year or so. I am paid to design systems that work, not systems that might work. > For sessions, session id in cookie and memcache/redis as session store works for all scale. >> Kind of a bold statement? GL with that. I don't know where you are getting your numbers from, but million pageviews/day as you mention again and again is a very nominal number for a generic webapp(unless you are very cache unfriendly viz. reddit). That isn't something you even have to think about. A standard rails app sitting behind nginx with 4-5 webservers will do it just fine. And for the last time, "session id in cookies and then load the session before request" fucking works for every one including facebook and google. The only thing that differs is choice of session store, and no, redis isn't the catchall solution. For most of the cases, memcache is faster.
- encoderer 14y agoWow, ego issues? You have taken this all very personally. I apologize for offering a different take on system design than what you apparently believe in very strongly? I've said a few times there's "no one way." The systems we've built have served over-billion-page-view months. That's not common or easy. HN is a site that values a back-and-forth about that kind of experience and I'd have loved to hear your tips thrown-out there too. But this has become some strange ego thing for you so it's time for me to bow out.
- deleted 14y ago[deleted]