[Bug]: port-forward for java remote debugger fails on first connect

[har-cpol]

Bug

Current behavior

I am deploying an application with sync mode enabled, and a port forward to connect the java remote debugger.

When connecting the java IDE to the remote JVM then the connection disconnects after about a second.
This only happens the first time - when connecting again the connection succeeds.

I suspect this is some racecondition in initialization of the port-forward on first connection.
On the first connect, I'm always getting twice the logs "Connecting to portforward...", followed by twice the logs "Connection from ... ended":
(The message "ended" appears about a second after connecting)

On client side, I'm getting disconnected

When connecting the second time, all works fine, and connect log only appears once (one additionl log line):

To reproduce this behavior you must use a java client - I could not reproduce the issue with a telnet connection.

The issue does not occur if I configure the port-forward with kubectl instead.

Expected behavior

JVM remote debugger should initialize correctly from the first time.

Reproducible example

Uploading a zip that reproduces the example.
It will start a simple java app that prints some text in an infinite loop.
Java is started with remote debugging enabled and a port forward via 127.0.0.1:5005 --> 5005

To test:

• run: garden -l=debug deploy portforward --sync portforward
• Connect a java IDE remote debugger to 127.0.0.1:5005

portforward.zip

Workaround

• use kubectl port-forward instead of garden port-forward
• or retry connect upon failure.

Suggested solution(s)

From the logs I suspect a race condition - seems like 2 outgoing connections are being configured.

Additional context

Your environment

• OS: linux (Fedora)
• How I'm running Kubernetes: locally with k0s, also occurs on google GKE

garden version: 0.13.45
(also tried with latest yesterday, same result)

[10ko]

Hi @har-cpol, thanks for this very detailed report and for the repro, we'll take a look in the coming days.