Can I have sticky sessions with HAProxy and socket.io with authentication?

Question

I have several instances of socket.io with authentication running under HAProxy and I need to force that the authentication request and the socket connection go to the same instance. I've set up HAProxy based on this answer to a SO question with some modifications as so:

global
    maxconn     4096 # Total Max Connections. This is dependent on ulimit
    nbproc      2

defaults
    mode        http

frontend all 0.0.0.0:80
    timeout client 86400000
    default_backend www_backend
    acl is_websocket hdr(Upgrade) -i WebSocket
    acl is_websocket hdr_beg(Host) -i ws

    use_backend socket_backend if is_websocket

backend www_backend
    balance url_param sessionId
    option forwardfor # This sets X-Forwarded-For
    timeout server 30000
    timeout connect 4000
    server server1 localhost:8081 weight 1 maxconn 1024 check
    server server2 localhost:8082 weight 1 maxconn 1024 check
    server server3 localhost:8083 weight 1 maxconn 1024 check

backend socket_backend
    balance url_param sessionId
    option forwardfor # This sets X-Forwarded-For
    timeout queue 5000
    timeout server 86400000
    timeout connect 86400000
    server server1 localhost:8081 weight 1 maxconn 1024 check
    server server2 localhost:8082 weight 1 maxconn 1024 check
    server server3 localhost:8083 weight 1 maxconn 1024 check

I've tried url_param (where sessionId is a querystring parameter passed in both the authentication call and the websocket connection) and source as the balance options but it seems as if HAProxy only allows these options for HTTP connections and so ignores them for the actual websocket connection. The result is that sometimes the auth request and the socket connection end up in different servers, which is unacceptable for our application.

Is there some way to have this desired behavior?

Answer 1

I use cookie based balancing in this way:

backend socketio
    mode http
    cookie SIO insert
    server sock1 127.0.0.1:8001 cookie 001
    server sock2 127.0.0.1:8002 cookie 002

Answer 2

To balance TCP connection, you may have some success with a stickiness table using the stick_match or stick on commands and explicitly setting tcp mode.

Here is an example:

# forward SMTP users to the same server they just used for POP in the
# last 30 minutes
backend pop
    mode tcp
    balance roundrobin
    stick store-request src
    stick-table type ip size 200k expire 30m
    server s1 192.168.1.1:110
    server s2 192.168.1.1:110

backend smtp
    mode tcp
    balance roundrobin
    stick match src table pop
    server s1 192.168.1.1:25
    server s2 192.168.1.1:25

Full documentation available here.