Improve Realm ID resolution for Quarkus 3.24+ (#2163)

In Quarkus 3.24, it is now possible to retrieve context locals inside HttpServerMetricsTagsContributor. This greatly simplifies our RealmIdTagContributor implementation.

It is also now possible to return null from ValueExpressionResolver. This is not a big deal, but still better than returning "".

Author: adutra

runtime/service/src/main/java/org/apache/polaris/service/quarkus/metrics/QuarkusValueExpressionResolver.java

@@ -31,14 +31,14 @@ public class QuarkusValueExpressionResolver implements ValueExpressionResolver {
   @Inject QuarkusMetricsConfiguration metricsConfiguration;
 
   @Override
+  @Nullable
   public String resolve(@Nonnull String expression, @Nullable Object parameter) {
     // TODO maybe replace with CEL of some expression engine and make this more generic
     if (metricsConfiguration.realmIdTag().enableInApiMetrics()
         && parameter instanceof RealmContext realmContext
         && expression.equals("realmIdentifier")) {
       return realmContext.getRealmIdentifier();
     }
-    // FIXME cannot return null here, see https://github.com/quarkusio/quarkus/issues/47891
-    return "";
+    return null;
   }
 }

runtime/service/src/main/java/org/apache/polaris/service/quarkus/metrics/RealmIdTagContributor.java

@@ -20,49 +20,25 @@
 
 import io.micrometer.core.instrument.Tags;
 import io.quarkus.micrometer.runtime.HttpServerMetricsTagsContributor;
-import io.vertx.core.http.HttpServerRequest;
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.inject.Inject;
 import org.apache.polaris.core.context.RealmContext;
-import org.apache.polaris.service.context.RealmContextResolver;
+import org.apache.polaris.service.quarkus.context.RealmContextFilter;
 
 @ApplicationScoped
 public class RealmIdTagContributor implements HttpServerMetricsTagsContributor {
 
   public static final String TAG_REALM = "realm_id";
 
-  private static final Tags UNFINISHED_RESOLUTION_TAGS = Tags.of(TAG_REALM, "???");
-
   @Inject QuarkusMetricsConfiguration metricsConfiguration;
-  @Inject RealmContextResolver realmContextResolver;
 
   @Override
   public Tags contribute(Context context) {
-    // FIXME retrieve the realm context from context.requestContextLocalData()
-    // after upgrading to Quarkus 3.24
     if (!metricsConfiguration.realmIdTag().enableInHttpMetrics()) {
       return Tags.empty();
     }
-    HttpServerRequest request = context.request();
-    try {
-      return realmContextResolver
-          .resolveRealmContext(
-              request.absoluteURI(),
-              request.method().name(),
-              request.path(),
-              request.headers()::get)
-          .thenApply(this::successfulResolutionTags)
-          .toCompletableFuture()
-          // get the result of the CompletableFuture if it's already completed,
-          // otherwise return UNFINISHED_RESOLUTION_TAGS as this code is executed on
-          // an event loop thread, and we don't want to block it.
-          .getNow(UNFINISHED_RESOLUTION_TAGS);
-    } catch (Exception e) {
-      return Tags.empty();
-    }
-  }
-
-  private Tags successfulResolutionTags(RealmContext realmContext) {
+    RealmContext realmContext =
+        context.requestContextLocalData(RealmContextFilter.REALM_CONTEXT_KEY);
     return Tags.of(TAG_REALM, realmContext.getRealmIdentifier());
   }
 }