[jetty-users] WebSocket connection/debugging issues

[Meggyesi, Zalán]

Hi,

I'm running a small-ish Ninja app under Java 11 using the latest Jetty, and
I'm running into trouble setting up a WebSocket connection, but I'm quite
stuck on how to debug it.

The app runs behind an Nginx reverse proxy, which adds back the Connection:
upgrade and Upgrade: websocket headers that would normally be stripped out,
but it's as if Jetty *itself* removed these before the connection is passed
to the application, because when I print the headers on the incoming
connection, the Upgrade header is missing, and so the application doesn't
know what to do with it, resulting in an eventual failed WS handshake.
Needless to say, this all happens with the websockets module enabled in the
installation.

I considered making a bug report, but I have *zero* evidence to back up my
claim of Jetty mishandling WS connections. Is there a debug or verbose
logging mode for Jetty itself, that could capture information as the
connection is being handled - that way I could at least find out if I'm
misconfiguring something.

Thanks in advance!

Best,
Zalan Meggyesi

[Joakim Erdfelt]

Need to know more details.

When you enable the `websocket` module on `jetty-home`/`jetty-base` a few
things happen.

1. The websocket JARs for the various APIs become available on the Server
classpath.
2. The websocket ServletContainerInitializers kick in to initialize various
things within the javax.servlet.ServletContext of your running webapp (via
use of a WebAppContext).

In the case of `javax.websocket.server` the discovered @ServerEndpoint
annotated classes are deployed (only with a WebAppContext).

There's nothing in your question that indicates if this is a websocket
server issue? or a websocket client issue?
Also, you don't indicate which API you are using. (the jetty native
websocket API, or the javax.websocket API)

If you are using websocket on server, put a breakpoint in WebSocketServlet
or WebSocketUpgradeFilter to see what's happening there (depends on what
API and technique for deployment you are using).

The tests for `isUpgradeRequest` is a good place to start debugging your
behaviors.

See:

https://github.com/eclipse/jetty.project/blob/jetty-9.4.14.v20181114/jetty-websocket/websocket-servlet/src/main/java/org/eclipse/jetty/websocket/servlet/WebSocketServlet.java#L158
https://github.com/eclipse/jetty.project/blob/jetty-9.4.14.v20181114/jetty-websocket/websocket-server/src/main/java/org/eclipse/jetty/websocket/server/WebSocketUpgradeFilter.java#L211

If the incoming request doesn't have the `Connection: upgrade` or `Upgrade:
websocket` then one of two things is happening.

1. The client didn't send it
2. or Something is stripping out those headers

As for that "something is stripping out those headers" part, that could be
a servlet Filter on your server side, it could be a Rewrite Rule that's
stripping out on your server side, or something in front of Jetty is
stripping them out.
A quick look through the code, there's nothing built into (or ships with)
Jetty that will strip out those headers.

Post by Meggyesi, Zalán
Hi,
I'm running a small-ish Ninja app under Java 11 using the latest Jetty,
and I'm running into trouble setting up a WebSocket connection, but I'm
quite stuck on how to debug it.
upgrade and Upgrade: websocket headers that would normally be stripped
out, but it's as if Jetty *itself* removed these before the connection is
passed to the application, because when I print the headers on the incoming
connection, the Upgrade header is missing, and so the application doesn't
know what to do with it, resulting in an eventual failed WS handshake.
Needless to say, this all happens with the websockets module enabled in the
installation.
I considered making a bug report, but I have *zero* evidence to back up
my claim of Jetty mishandling WS connections. Is there a debug or verbose
logging mode for Jetty itself, that could capture information as the
connection is being handled - that way I could at least find out if I'm
misconfiguring something.
Thanks in advance!
Best,
Zalan Meggyesi
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