Wikipedia:Reference desk/Archives/Computing/2021 May 14

= May 14 =

"Website is down" status page
Imagine that a major organisation's website has to be taken down for maintenance for a few days. The developers don't want their organisation's website to return 404 errors, so they put up a page that says "this page is undergoing maintenance; we'll be back soon". How does such a page work? Do the developers route requests for server #1 (which is offline) to server #2 (which gives the outage message), or is there a better way to do it? Context: Ebsco took down a lot of their site for maintenance several days ago, so pages like https://ecm.ebscohost.com are currently saying "we're doing maintenance, check https://status.ebsco.com for updates", and I'm just curious how a server can be both online (so it gives this message) and offline (so it doesn't let me use the site like normal) at the same time.

When I search Google for information, all I'm finding is either "what does this status page mean" pages, for new Internet users who encounter them, or "use our status page generator" pages, for companies that offer such pages as a service. Nothing appears to explain how it works. Nyttend backup (talk) 20:00, 14 May 2021 (UTC)
 * Many websites are multiple servers behind a load balancer (or a pair of them). The LB takes each inbound request and passes it onward to one of the servers - sometimes in rotation, sometimes to the "least busy" one. During normal operation, the LB checks each of the servers at intervals and asks it if it is happy. If one is unwell, then the requests go to the others. If none of the webservers are happy, then the LB has the option to return the "It has all gone Horribly Wrong!" page. In practice, it is best to schedule maintenance for each server in turn, so that the LB always has other servers to call on — GhostInTheMachine talk to me 21:10, 14 May 2021 (UTC)


 * In the example you give, the server is returning the HTTP status "503 Service Unavailable". I haven't configured a web server for a while, but I expect there's a setting in the server software (they report using Microsoft-IIS/8.5) that allows this status to be returned for any request, and IIS allows you to associate a particular HTML file with an error code such as 503. So the site, or rather the server, is "online", but routing all requests to the notification page. AndrewWTaylor (talk) 11:23, 17 May 2021 (UTC)