OpenTracing Jaeger: Probabilistic sampler didn't work

[loicmathieu]

Describe the bug

When using a probabilistic sample (with 0.5 as sampling rate) no traces are generated.
When using a constant sampler (with 1 as sampling rate) traces are correctly generated.

Expected behavior

We can use a probabilistic sampler in Quarkus.

Actual behavior

No response

How to Reproduce?

Steps to reproduce:

1. Download the sample project (configured with a probabilistic sampler, see
   https://www.jaegertracing.io/docs/1.22/sampling/#client-sampling-configuration): jaeger-probabilistic-sampler.zip
2. Start Jaeger: docker run -p 5775:5775/udp -p 6831:6831/udp -p 6832:6832/udp -p 5778:5778 -p 16686:16686 -p 14268:14268 jaegertracing/all-in-one:latest
3. Start the applicaiton via mvn quarkus:dev
4. Call the endpoint a few times: curl localhost:8080/hello
5. Go to the Jager UI (should be on port 16686): nothing shows up!

If you switch to a constant sampler, traces will shows up, you can verify this by updating the configuration with

quarkus.jaeger.sampler-type=const
quarkus.jaeger.sampler-param=1

Output of uname -a or ver

Microsoft Windows [version 10.0.19042.1237]

Output of java -version

openjdk version "17" 2021-09-14

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.3.1.Final

Build tool (ie. output of mvnw --version or gradlew --version)

Apache Maven 3.6.3

Additional information

No response

[quarkus-bot]

/cc @Ladicek, @radcortez

[radcortez]

Hum, I've followed the repro steps and it seems to work fine for me:

Can you confirm?

[radcortez]

The only difference that I have is the OS. Let me see if I can dig up a Windows VM to try that out.

[loicmathieu]

I'll ask on Monday one of my colleagues that have a Mac to test and see if it works.

[radcortez]

I was able to try this on my Windows VM and it also works... wondering if it may be a difference in the jaeger docker image we are getting? I would expect it would be the same for both of us.

[radcortez]

Any update on this?

[loicmathieu]

Just tried it on my Windows laptop using Quarkus 2.6.1 and I can reproduce the issue.

[loicmathieu]

Just tried also on my Linux laptop and I can also reproduce the issue.

[loicmathieu]

Using tcpdump I can clearly see that when using probabilistic sampler no UDB packet are sent to the port 6831 but when using constant sampler I can see the packets.

[radcortez]

Ok, I'll have another look.

[loicmathieu]

Thanks

[radcortez]

We were able to determine that this is caused by writing the probabilistic value in format, that the Jaeger configuration would not read property due to the default Locale.