Race condition between Java server startup and Langium LSP server

[riteshkumar2002]

In my project I use both a Java server (for dependency management / Maven resolution) and a Langium-based LSP server.
Currently, when I run my project, both servers start at the same time.

The problem:
The Java server needs to download Maven dependencies (from pom.xml) during startup.
So if their is any issue in java the lsp server fails and start re-connecting.
This leads to inconsistent startup behavior — sometimes it works, sometimes it fails, depending on how long the Java server takes to initialize.

[msujew]

Hey @riteshkumar2002,

I couldn't quite follow your description. Can you give a bit more context? Why does your language server crash because of Maven dependencies? The language server should be coded in a way that it can handle changes to the workspace/file system without crashing.

[riteshkumar2002]

Hello @msujew
I am using both a Langium LSP server and the RedHat Java extension (added via the VSIX package redhat.java-1.36.2024101604
) for Maven/Java dependency management.
When the workspace initializes, both servers (Langium LSP + Java) start together.
If the Java server encounters an issue (for example, while downloading or resolving Maven dependencies), it negatively affects the LSP server. This leads to failures and reconnection attempts by the LSP server, even though the LSP itself should ideally work independently of the Java server.
How can I decouple the LSP server from the Java server so that:
The LSP server does not fail or restart if the Java server has issues.

[msujew]

If the Java server encounters an issue (for example, while downloading or resolving Maven dependencies), it negatively affects the LSP server. This leads to failures and reconnection attempts by the LSP server, even though the LSP itself should ideally work independently of the Java server.

I fail to understand how the Java server and the Langium based language server are connected. They run in separate processes - how are they interacting with one another? Please give a full picture of the issue you're experiencing.

[riteshkumar2002]

Hello,

I am working with a Theia-based application where both a Langium-based project and the Java extension have been integrated as plugins. However, if the Java plugin crashes for any reason, it also causes my Langium LSP to crash. Could you please guide me on how to isolate or resolve this issue so that one plugin’s failure does not affect the other?

Thanks in advance

[msujew]

Do you get any error that the extension host has crashed in Theia? Can you try to reproduce this in VS Code? Does the same happen there?

Aside from that, can you provide a reproducible example? Perhaps some code of your language server? Because it sounds like there's an uncaught error in the language server somewhere, i.e. a missing await or similar.