Observed "Could not hpack encode HTTP/2.0" exception with junit console launcher

[cutefish]

Jetty version
11.0.15

Java version
11

Question
First, let me explain what I am doing. I have created a maven repository to do
some http related tests and I am using jetty for an http2 server. I am using
JUnit 5 for the unit tests. The tests runs successfully under maven. No errors.
For the next step, I would like to run the tests on another machine.
Configuring maven on that machine to obtaining dependencies is a bit of
a hassle, so I thought I could use the JUnit Console Launcher
(https://junit.org/junit5/docs/current/user-guide/#running-tests-console-launcher).
So I package the test jar with dependencies of the maven project and run the
following command with both the junit console launcher jar and my test jar like
the following:

java -jar jpcs.jar -cp httpperf-1.0.0-test-jar-with-dependencies.jar --select-method httpperf.JettyClientTest#testSyncHttp2

And I have observed the following stack trace in my test.

[qtp1432569632-28] DEBUG org.eclipse.jetty.http2.HTTP2Flusher - Failure generating HeadersFrame@46477305#1[end=false,{HTTP/2.0{s=200,h=12,cl=-1}},priority=null]
org.eclipse.jetty.http2.hpack.HpackException$SessionException: Could not hpack encode HTTP/2.0{s=200,h=12,cl=-1}
        at org.eclipse.jetty.http2.hpack.HpackEncoder.encode(HpackEncoder.java:278)
        at org.eclipse.jetty.http2.generator.FrameGenerator.encode(FrameGenerator.java:56)
        at org.eclipse.jetty.http2.generator.HeadersGenerator.generateHeaders(HeadersGenerator.java:65)
        at org.eclipse.jetty.http2.generator.HeadersGenerator.generate(HeadersGenerator.java:52)
        at org.eclipse.jetty.http2.generator.Generator.control(Generator.java:86)
        at org.eclipse.jetty.http2.HTTP2Session$ControlEntry.generate(HTTP2Session.java:1245)
        at org.eclipse.jetty.http2.HTTP2Flusher.process(HTTP2Flusher.java:215)
        ...
Caused by: java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
        at org.eclipse.jetty.http.PreEncodedHttpField.putTo(PreEncodedHttpField.java:121)
        at org.eclipse.jetty.http2.hpack.HpackEncoder.encode(HpackEncoder.java:377)
        at org.eclipse.jetty.http2.hpack.HpackEncoder.encode(HpackEncoder.java:249)
        ... 50 more

I did a bit googling and find there are related tickets (e.g.,
#9168) which points to the
HpackFieldEncoder class not being loaded.

Debugging it myself, I can confirm that my test jar contains the class. When
I explicitly does ServiceLoader.load(HttpFieldPreEncoder.class) before the
test, it does not help. I also tried to add
-Dorg.eclipse.jetty.http.PreEncodedHttpField.LEVEL=DEBUG to see if the class
is loaded as is suggested by one of those related tickets, but I did not see
anything related.

Please advise what I should do to fix or debug this issue. Thanks a lot.

[lachlan-roberts]

It would be good if we could see all debug logs from PreEncodedHttpField.

We should always see this log line:

LOG.debug("HttpField encoders loaded: {}", encoders);

and if there were any errors loading the HTTP/2 pre-encoder we should see this one as well

LOG.debug("Unable to add HttpFieldPreEncoder", e);

[lachlan-roberts]

When I explicitly does ServiceLoader.load(HttpFieldPreEncoder.class) before the
test, it does not help.

when you did this did it load HpackFieldPreEncoder?

[sbordet]

HttpFieldPreEncoder is loaded via the service loader mechanism.

Yoou must ensure that http2-hpack.jar is in the classpath, because it is not only the class that matters, but also the service loader file.

[cutefish]

Adding the http2-hpack.jar to the classpath worked. Thanks a lot.