If my servers get overloaded, how hard is it to get my site back up?

Question

If my servers get many visitors, and it can't handle the traffic, what would happen to the site, and how do I get it back up?

Answer 1

Getting your site back up depends on exactly what happened:

• If your provider allows for 10 Mbps bandwidth, each connection will have to share that bandwidth, so if you have 10,000 people all downloading at the same time, each download will be slow. When the downloads finish, everything will return to normal again.
• If your provider allows for 10GB of data transfer a month and you use that up, they'll likely turn off your site until you pay them for more data.
• If your server only allows 1000 connections at once, the 1001st person who tries to connect will have to wait until there's an opening, and either timeout or just get slow page loads. Once there are openings, everything returns to normal again.
• If the server runs out of RAM then an important process may crash or be killed. In this case, an admin may have to restart that process.
• While it's unlikely with well-built systems in well-cooled facilities, if the server heats up under load, then high load may cause heat damage (failed drives, damaged processors, etc) that might require replacing the system.

Answer 2

If you expect to get a lot of visits from Launch, then it is probably worth doing some performance testing and scale up as much as you can afford.

As far as what happens, if you get way more traffic then you can handle your sites will be down for all practical purposes too all users. To limit the damage you could put a rate limiter in front of your servers, so at least a certain amount of people can use the site. If these are web servers, then you might have a look at HAProxy rate limiting.

Always consider caching as much as possible, this can allow you to handle a lot more load if your application is such that caching can be used.

Answer 3

Nothing more than visitors will have to wait or even can't see your site content wouldn't happen. You have to optimize your web stack or upgrade your hardware/balance traffic

Answer 4

Some web frameworks/setups are subject to positive load feedback effects, these can require manual intervention to get the site back up even if traffic has lowered again (lingering requests, for example to backend databases, still retrying, left from the load bursts, cause new requests to have far less of a budget, resulting in a smaller number of requests needed to drive the application over the edge again...)

If load balancers are involved: Nodes going offline from overload will leave even less nodes to deal with the onslaught...

Cache stampeding effecs somewhere in the stack can also cause very unstable behaviour.