Cloudflare HTTP POST 524带有node.js + express的超时

Question

I am having a trouble using HTTP POST when cloudflare is enabled. It keeps returning 524 timeout.

Failed to load resource: the server responded with a status of 524 (Origin Time-out) 

But when I disabled cloudflare, the HTTP POST works fine.

Any idea what might caused this?

UPDATE

I am using AJAX POST, does this got anything to do with ajax?

Thanks.

Answer 1

General causes for a CloudFlare 524 error .

Support should be able to provide more detailed troubleshooting.

Answer 2

Console utility "netstat" shows that some connections from CloudFlare are in CLOSE_WAIT state. Pointing that server just sits without correctly closing connections. Looking to the TCP traffic of my web server with Message Analyzer, I found several connections that was established and http request was sent but that wasn't ever processed by my server.

So we get an answer: the number of simultaneously established connections outnumbered available Accept() calls. So TCP stack connects and wait while application will handle it's connection. Depending on the situation this can never happen, so the client side just drops this connection after a 30 sec timeout without getting any response.

To fix this, you must increase the number of outstanding possible accepts . This parameter can be named as "Max simultaneous connections number" or something similar. Check your web server documentation \\ ask the support to find it out.

Also, as an experiment, you can force your server to reply with the "Connection:close" header to each request. This may prevent reaching the active connections limit problem because CloudFlare keep-alive them just way too long.

Also, the more simultaneous requests you do, the more probability to get in troubles. You can try to set some small webserver-side timeout for idle connections.

PS: Illustration of CloudFlare's connections number after one client loaded a page: ( http://i.imgur.com/IgwGLCf.png )