Unable to serve file when Content-Length is specified

[martin-sladecek]

In some cases, when Content-Length is specified, the server request gets stuck and no response is returned.

Environment Details

• Helidon Version: 3.2.0
• Helidon MP
• JDK version: 17
• OS: Linux
• Docker version (if applicable):

---

Problem Description

Sample:
sample.zip

Using the sample, it is possible to reproduce this in 2 ways:

1. Run the test
2. Run the app and call /greet endpoint with curl. The request will be stuck and no response is sent, not even headers.

Alternatively, I've tried netcat to send the request manually. Interestingly, when I add 2 newlines after the GET request line, the server starts to send the data.

Steps to reproduce

See problem description above.

[barchetta]

Two observations:

1. The reproducer seems to work with Helidon 4.0.0-ALPHA5 so maybe that points the finger at Helidon code?
2. I think there is a typo in the app. io.helidon.common.http.Http.Header should be jakarta.ws.rs.core.HttpHeaders. I don't think it is causing a problem, but it is not correct.

[spericas]

@martin-sladecek Could you try turning off back pressure in microprofile-config.properties as follows?

server.backpressure-strategy=UNBOUNDED

[martin-sladecek]

Hi @spericas, the property seems to work.

[spericas]

@martin-sladecek Great, it is a workaround. There's a bug in the default backpressure strategy that I'm looking into.

[martin-sladecek]

None of the backpressure strategies work, not just the default one.

[spericas]

The other two would require changes to the code, and some explicit flushing (better suited for SE). AUTO_FLUSH is the default one and should work fine in MP.

[spericas]

PR #6556