provide a way to extract last logged event via logging in duplicates …

…admin monitor (checking if this is the best, if yes then will write a test for it)

src/main/java/org/jenkinsci/plugins/github/admin/GitHubDuplicateEventsMonitor.java

@@ -1,5 +1,7 @@
 package org.jenkinsci.plugins.github.admin;
 
+import java.util.logging.Logger;
+
 import hudson.Extension;
 import hudson.model.AdministrativeMonitor;
 import jenkins.model.Jenkins;
@@ -10,6 +12,9 @@
 @Extension
 public class GitHubDuplicateEventsMonitor extends AdministrativeMonitor {
 
+    private static final Logger LOGGER = Logger.getLogger(GitHubDuplicateEventsMonitor.class.getName());
+    private static String previouslyLoggedEventId;
+
     @Override
     public String getDisplayName() {
         return Messages.duplicate_events_administrative_monitor_displayname();
@@ -25,7 +30,17 @@ public String getBlurb() {
 
     @Override
     public boolean isActivated() {
-        return DuplicateEventsSubscriber.isDuplicateEventSeen();
+        boolean isActivated = DuplicateEventsSubscriber.isDuplicateEventSeen();
+        if (isActivated) {
+            var curDuplicate = DuplicateEventsSubscriber.getLastDuplicate();
+            if (!curDuplicate.eventGuid().equals(previouslyLoggedEventId)) {
+                LOGGER.finest(() -> {
+                    previouslyLoggedEventId = curDuplicate.eventGuid();
+                    return "Latest tracked event payload: " + curDuplicate.ghSubscriberEvent().getPayload();
+                });
+            }
+        }
+        return isActivated;
     }
 
     @Override

src/main/java/org/jenkinsci/plugins/github/webhook/subscriber/DuplicateEventsSubscriber.java

@@ -38,8 +38,7 @@ public final class DuplicateEventsSubscriber extends GHEventsSubscriber {
     private static final Map<String, Long> EVENT_TRACKER = new ConcurrentHashMap<>();
     private static volatile TrackedDuplicateEvent lastDuplicate;
 
-    @VisibleForTesting
-    record TrackedDuplicateEvent(String eventGuid, long lastUpdated, GHSubscriberEvent ghSubscriberEvent) { }
+    public record TrackedDuplicateEvent(String eventGuid, long lastUpdated, GHSubscriberEvent ghSubscriberEvent) { }
 
     /**
      * This subscriber is not applicable to any item
@@ -113,9 +112,7 @@ static Map<String, Long> getEventCountsTracker() {
         return Collections.unmodifiableMap(EVENT_TRACKER);
     }
 
-    @VisibleForTesting
-    @Restricted(NoExternalUse.class)
-    static TrackedDuplicateEvent getLastDuplicate() {
+    public static TrackedDuplicateEvent getLastDuplicate() {
         return lastDuplicate;
     }
 

src/main/resources/org/jenkinsci/plugins/github/Messages.properties

@@ -15,4 +15,5 @@ duplicate.events.administrative.monitor.displayname=GitHub Duplicate Events
 duplicate.events.administrative.monitor.description=Warns about duplicate events received from GitHub.
 duplicate.events.administrative.monitor.blurb=Duplicate events were received from GitHub, possibly due to \
   misconfiguration (e.g., multiple webhooks targeting the same Jenkins controller at the repository or organization \
-  level), potentially causing redundant job executions.
+  level), potentially causing redundant job executions. To inspect the last tracked duplicate event payload, \
+  enable logging at the `FINEST` level for the class `org.jenkinsci.plugins.github.admin.GitHubDuplicateEventsMonitor`.