Configuring Apache 2.4 mod_proxy_wstunnel for Socket.IO 1.0

Question

I'm trying to configure Apache 2.4 for proxying the websocket connection for socket.io to a node.js websocket server, using mod_proxy_wstunnel. We had this working fine with socket.io 0.9, but with the 1.0 release they changed the socket endpoint to a query parameter, and now I'm having trouble configuring apache with the correct proxy instructions.

All requests to /socket.io/?EIO=N&transport=websocket (where N is any digit, usually 2) need to be forwarded to ws://localhost:8082/socket.io/, but all other requests need to be forwarded to http://localhost:8082/socket.io/.

I've tried variations of both of the following configs:

ProxyPass /socket.io/?EIO=2&transport=websocket http://localhost:8082/socket.io/?EIO=2&transport=websocket
ProxyPassReverse /socket.io/?EIO=2&transport=websocket http://localhost:8082/socket.io/?EIO=2&transport=websocket

ProxyPass /socket.io/ http://localhost:8082/socket.io/
ProxyPassReverse /socket.io/ http://localhost:8082/socket.io/

.

RewriteRule /socket.io/?EIO=([0-9]+)&transport=websocket ws://localhost:8082/socket.io/ [QSA,P]

ProxyPass /socket.io/ http://localhost:8082/socket.io/
ProxyPassReverse /socket.io/ http://localhost:8082/socket.io/

I've gathered from my googling that ProxyPass and Locations can't target query strings, so is there any other option here? The paths are hard-coded into socket.io, so short of forking the entire library I can't change them.

Solution

Use Rewrite conditions to match for this special case:

RewriteEngine On
RewriteCond %{REQUEST_URI}  ^/socket.io            [NC]
RewriteCond %{QUERY_STRING} transport=websocket    [NC]
RewriteRule /(.*)           ws://localhost:8082/$1 [P,L]

ProxyPass        /socket.io http://localhost:8082/socket.io
ProxyPassReverse /socket.io http://localhost:8082/socket.io

NOTE As Mark W noted below. These must be entered at vhost level and not at server or .htaccess level.

You can also reference a balancer:

<Proxy balancer://http-localhost/>
    BalancerMember http://localhost:8082 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
    BalancerMember http://localhost:8083 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
    ProxySet lbmethod=bytraffic
</Proxy>

<Proxy balancer://ws-localhost/>
    BalancerMember ws://localhost:8082 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
    BalancerMember ws://localhost:8083 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
    ProxySet lbmethod=bytraffic
</Proxy>

RewriteEngine On
RewriteCond %{REQUEST_URI}  ^/socket.io                [NC]
RewriteCond %{QUERY_STRING} transport=websocket        [NC]
RewriteRule /(.*)           balancer://ws-localhost/$1 [P,L]

ProxyPass        /socket.io balancer://http-localhost/socket.io
ProxyPassReverse /socket.io balancer://http-localhost/socket.io

Comments

[Eamorr]

+100000 You made my day. Been at this for hours. I used the first code snippet. I don't need a balancer at the moment.

[ChiperSoft]

I'm not able to get this to work. Apache keeps responding with a 404 code. It shows up in the access log as if it's trying to load a normal file, and the socket node process shows no sign of receiving the request (it does show the call for the socket.io.js file)

[ChiperSoft]

It appears that mod_rewrite doesn't know the ws:// protocol. I see this in my rewrite log: forcing proxy-throughput with http://[REDACTED].dev/ws://localhost:8082/socket.io/ (domain.dev

[ChiperSoft]

This is probably why: issues.apache.org/bugzilla/show_bug.cgi?id=55598 Looks like support for the protocol was added in Apache 2.5

[PeterPramb]

Which version are you using? I'm using the rewrites above with 2.4.10 with no problems.

[lkraav]

This is definitely the right stuff and works even on 2.2-series with the mod_proxy websockets backport. Additional discussion github.com/Automattic/socket.io/issues/1696

[Jake Z]

NOTE: These blocks should be placed within the <VirtualHost> block in the exact order described, even if you are using the document root (e.g. /var/www/html). I spent nearly 2 hours trying to figure out why these changes were not working properly, only to find out that the RewriteRule's were not functioning at the root level of httpd.conf (although ProxyPass was working). The ProxyPass directives do not work in <Directory> blocks or .htaccess files (although the RewriteRule's do), so the logical place to group these changes is in <VirtualHost>.

[kojow7]

When using a load balancer like this I can no longer detect when clients pages are closed in a timely manner. If I connect directly I can tell instantly, if I go through a load balancer proxy like this it takes over a minute before I can tell they've closed their browser page.

[gbenroscience]

@PeterPramb , please, could you help me out with stackoverflow.com/questions/70210654/…