I am running websocket connections via mod_proxy_wstunnel to a backend application server. Apache works as a reverse proxy.

After running for some time, I get 500 errors from the backend server for new client connection attempts.

Root cause is that mod_proxy_wstunnel reuses the connections to the backend server.

When the client attempts a new connection, mod_proxy_wstunnel forwards the initial GET request of the websocket handshake to the backend, on a connection which has already been handshook. The backend server is not prepared for a new handshake on a handshook connection and replies with a 500 error.

Workaround:
Use disablereuse=on for the ProxyPass directive.

Possible solutions:
I think connection reuse should be disabled altogether for websocket connections (except the websocket protocol somehow allows it). mod_proxy_wstunnel should either fail on startup when connection reuse is enabled, or alternatively, always request a fresh backend connection, regardless of the disablereuse setting.