distinguish failed resolution from unresolved

Author: adutra

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

@@ -21,7 +21,6 @@
 import io.micrometer.core.instrument.Tags;
 import io.quarkus.micrometer.runtime.HttpServerMetricsTagsContributor;
 import io.vertx.core.http.HttpServerRequest;
-import jakarta.annotation.Nullable;
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.inject.Inject;
 import org.apache.polaris.core.context.RealmContext;
@@ -31,6 +30,10 @@
 public class RealmIdTagContributor implements HttpServerMetricsTagsContributor {
 
   public static final String TAG_REALM = "realm_id";
+  public static final String TAG_REALM_RESOLUTION_FAILURE = "realm_resolution_failure";
+
+  private static final Tags UNFINISHED_RESOLUTION_TAGS = Tags.of(TAG_REALM, "???");
+  private static final Tags FAILED_RESOLUTION_TAGS = Tags.of(TAG_REALM, "!!!");
 
   @Inject RealmContextResolver realmContextResolver;
 
@@ -39,26 +42,31 @@ public Tags contribute(Context context) {
     // FIXME request scope does not work here, so we have to resolve the realm context manually
     HttpServerRequest request = context.request();
     try {
-      RealmContext realmContext = resolveRealmContext(request);
-      return realmContext == null
-          ? Tags.empty()
-          : Tags.of(TAG_REALM, realmContext.getRealmIdentifier());
-    } catch (Exception ignored) {
-      // ignore, the RealmContextFilter will handle the error
-      return Tags.empty();
+      return realmContextResolver
+          .resolveRealmContext(
+              request.absoluteURI(),
+              request.method().name(),
+              request.path(),
+              request.headers()::get)
+          .thenApply(this::successfulResolutionTags)
+          .exceptionally(this::failedResolutionTags)
+          .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 failedResolutionTags(e);
     }
   }
 
-  @Nullable
-  private RealmContext resolveRealmContext(HttpServerRequest request) {
-    return realmContextResolver
-        .resolveRealmContext(
-            request.absoluteURI(), request.method().name(), request.path(), request.headers()::get)
-        .exceptionally(error -> null)
-        .toCompletableFuture()
-        // get the result of the CompletableFuture if it's already completed,
-        // otherwise return null as this code is executed on an event loop thread,
-        // and we don't want to block it.
-        .getNow(null);
+  private Tags successfulResolutionTags(RealmContext realmContext) {
+    return Tags.of(TAG_REALM, realmContext.getRealmIdentifier());
+  }
+
+  private Tags failedResolutionTags(Throwable error) {
+    return FAILED_RESOLUTION_TAGS.and(
+        TAG_REALM_RESOLUTION_FAILURE,
+        error.getMessage() == null ? error.getClass().getSimpleName() : error.getMessage());
   }
 }