How to disable trace ids for specific REST Clients invocations?

Question

Currently, when using REST Client to do API calls and Open Telemetry extension for tracing, a tracing header is added to all API calls, which is fine.

However, in case I want to explicitly omit the addition of this header when interacting with third party systems (externals / not in my control), is there any annotation (method or class level) I can use? If not, is there any way to omit it?

Answer 1

For this purpose, OpenTelemetry uses a Sampler.

You can create your own CDI bean sampler with Quarkus, like this:

@Singleton
public class CustomConfiguration {

    /** Creates a custom sampler for OpenTelemetry */
    @Produces
    @Singleton
    public Sampler sampler() {
        List<String> targets = List.of("http://address-you-must-drop");
        return new CustomSampler(targets);
    }
 }

Where the CustomSampler could be inspired by Quarkus own target sampler. It would look something like:

public class CustomSampler implements Sampler {

private final List<String> dropTargets;

public CustomSampler(final List<String> dropTargets) {
    // The targets to drop.
    this.dropTargets = dropTargets;
}

@Override
public SamplingResult shouldSample(Context context,
        String s,
        String s1,
        SpanKind spanKind,
        Attributes attributes,
        List<LinkData> list) {
    if (spanKind.equals(SpanKind.CLIENT)) {
        String target = attributes.get(SemanticAttributes.HTTP_URL);
        if (target == null) {
            target = attributes.get(SemanticAttributes.URL_FULL);
        }
        if (shouldDrop(target)) {
            return SamplingResult.drop();
        }
    }
    return Sampler.alwaysOn().shouldSample(context, s, s1, spanKind, attributes, list);
}

@Override
public String getDescription() {
    return "custom-endpoint-sampler";
}

private boolean shouldDrop(String target) {
    if ((target == null) || target.isEmpty()) {
        return false;
    }
    if (safeContains(target)) { // check exact match
        return true;
    }
    if (target.charAt(target.length() - 1) == '/') { // check if the path without the ending slash matched
        if (safeContains(target.substring(0, target.length() - 1))) {
            return true;
        }
    }
    int lastSlashIndex = target.lastIndexOf('/');
    if (lastSlashIndex != -1) {
        if (safeContains(target.substring(0, lastSlashIndex) + "*")
                || safeContains(target.substring(0, lastSlashIndex) + "/*")) { // check if a wildcard matches
            return true;
        }
    }
    return false;
}

private boolean safeContains(String target) {
    return dropTargets.contains(target);
}

}