Constantly reconnecting to websocket / session id unknown / Etherpad

Question

Problem

We are using Etherpad-lite on an Apache 2.4.18 and experiencing several reconnection attempts per minute. Etherpad shows a message that says

Reconnecting to your pad..

followed by

Connected

Context

The connection to the websocket is realized via a reverse proxy, set in the Apache configuration, that redirects the urls to the port Etherpad is running. A network analysis showed that Etherpad is having trouble with validating the session id. The request structure is always as followed:

Failing requests:

The selected GET-Request comes back with a "Code:1 Session Id unknown". Etherpad is then requesting a new sid and the process repeats. The Server Log is showing no suspicious errors other than access logs, so I also tried debugging via browser console which gave me the following output:

engine.io-client:socket socket error {"type":"Transport Error","description":400}
socket.io-client:manager Error:xhr poll error
Transport.prototype.onError@..../pad/socket.io/socket.io.js:5433:14

I don't know if this problem is related to Etherpad or to an Apache/socket.io misconfiguration, but i already asked this on github (see here for more details: https://github.com/ether/etherpad-lite/issues/3246) and got no answer.

Does anyone have a clue what is going wrong here?

Answer 1

To whom it may concern: Found the error myself, reason was a mistake in the configuration of my reverse proxy. I used the wrong protocol to access the websocket (had to use "wss:" via ssl instead of "ws:")