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?
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);
}
}