socket.io: Question: What could be the possible reasons for socket-io server returning 400 Bad Request via nginx?

Hi,

We are facing a scenario where a good percentage of requests going to /Socket.io/?... is returning with 400.

Default nginx access log results are littered with:

10.0.0.82 - - [04/Dec/2015:11:43:27 +0000] "GET /socket.io/?__sails_io_sdk_version=0.11.0&__sails_io_sdk_platform=browser&__sails_io_sdk_language=javascript&EIO=3&transport=websocket HTTP/1.1" 400 45 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"

The requests are not even reaching our overlying SailsJS server. We suspect something going wrong at socket-io layer. Any thought?

About this issue

Original URL
State: closed
Created 9 years ago
Comments: 29 (3 by maintainers)

Most upvoted comments

After a LOT of painstaking log-watching, this is our temporary solution for nginx config (to stop freaking out our servers.) The following directive checks for missing “Upgrade” header in request and returns with a 202 without hitting the node server.

location /socket.io {
    set $local_upgrade_failure "${arg___sails_io_sdk_platform}${arg_transport}${connection_upgrade}";
    if ( $local_upgrade_failure = "browserwebsocket" ) { return 202; break; }

 ... remain proxy configurations
}

Now, this does NOT fix the clients that are sending these requests, but surely frees up the server. Now, the question is @rauchg, why are some socket.io clients not sending the “upgrade” header? One pattern is that they are all Windows and a very few Linux machines. Did not spot a single OSX in one full hour of heavy usage.

shamasis on Dec 5, 2015

I will then have to deep dive into socket.io - it’s being returned by socket.io with no additional message -

{ code: 3, message: “badRequest”}

shamasis on Jun 12, 2016

I was having the very same issue, I faced this error when i was proxy my NodJS api from http://baseurl/api. Apparently I was missing ; (semicolons) at the end of nginx configs.

I was doing

proxy_http_version 1.1
proxy_set_header Upgrade $http_upgrade
proxy_set_header Connection "upgrade"

What worked

proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

Yep missing semicolons; Please double check ur configs

arfanliaqat on Oct 5, 2019

The bug has been reported (and ignored) upstream: socketio/engine.io#283

There is no workaround. Clients will drop to xhr for that session. If using nginx and you run into “no live upstreams”, this is the cause, so a workaround is to set max_fails to 0, so nginx never considers the upstream “down”. Hacky workaround (esp. if your upstream ever does go down), but there it is.

julianlam on Aug 8, 2016

Interesting discovery: The upgrade header is blank for the requests having 400 response. Forcing upgrade header to websocket stops the 400, but causes intermittent 499 error on nginx.

shamasis on Dec 5, 2015