Avoid hard-reference to Config in RemoteHostnameAdder because it causes issues with Quarkus builds using GraalVM. (#7480)

Instead we use the Supplier API to keep the hostname lookup lazy while avoiding eager analysis of the Config class.

Note we deliberately avoid using a method-reference to Config because that can also lead to unexpected resolution.

Author: mcculls

dd-trace-core/src/main/java/datadog/trace/core/tagprocessor/RemoteHostnameAdder.java

@@ -1,22 +1,22 @@
 package datadog.trace.core.tagprocessor;
 
-import datadog.trace.api.Config;
 import datadog.trace.api.DDTags;
 import datadog.trace.core.DDSpanContext;
 import java.util.Map;
+import java.util.function.Supplier;
 
 public class RemoteHostnameAdder implements TagsPostProcessor {
-  private final Config config;
+  private final Supplier<String> hostnameSupplier;
 
-  public RemoteHostnameAdder(Config config) {
-    this.config = config;
+  public RemoteHostnameAdder(Supplier<String> hostnameSupplier) {
+    this.hostnameSupplier = hostnameSupplier;
   }
 
   @Override
   public Map<String, Object> processTags(
       Map<String, Object> unsafeTags, DDSpanContext spanContext) {
     if (spanContext.getSpanId() == spanContext.getRootSpanId()) {
-      unsafeTags.put(DDTags.TRACER_HOST, config.getHostName());
+      unsafeTags.put(DDTags.TRACER_HOST, hostnameSupplier.get());
     }
     return unsafeTags;
   }

dd-trace-core/src/main/java/datadog/trace/core/tagprocessor/TagsPostProcessorFactory.java

@@ -17,7 +17,7 @@ private static TagsPostProcessor create() {
       }
       processors.add(new QueryObfuscator(Config.get().getObfuscationQueryRegexp()));
       if (addRemoteHostname) {
-        processors.add(new RemoteHostnameAdder(Config.get()));
+        processors.add(new RemoteHostnameAdder(Config.get().getHostNameSupplier()));
       }
       return new PostProcessorChain(
           processors.toArray(processors.toArray(new TagsPostProcessor[0])));

internal-api/src/main/java/datadog/trace/api/Config.java

@@ -540,6 +540,7 @@
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import javax.annotation.Nonnull;
@@ -585,6 +586,10 @@ static class RuntimeIdHolder {
 
   static class HostNameHolder {
     static final String hostName = initHostName();
+
+    public static String getHostName() {
+      return hostName;
+    }
   }
 
   private final boolean runtimeIdEnabled;
@@ -2272,6 +2277,10 @@ public String getHostName() {
     return HostNameHolder.hostName;
   }
 
+  public Supplier<String> getHostNameSupplier() {
+    return HostNameHolder::getHostName;
+  }
+
   public String getServiceName() {
     return serviceName;
   }