From c06615c3917206e2e1bb1c7b4801c2d26a734d75 Mon Sep 17 00:00:00 2001
From: Allan Burdajewicz <aburdajewicz@cloudbees.com>
Date: Fri, 26 Jul 2024 16:43:13 +1000
Subject: [PATCH] [#635][#683] Launch collector registration asynchronously

---
 .../service/DefaultPrometheusMetrics.java     | 47 ++++++++++++-------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/src/main/java/org/jenkinsci/plugins/prometheus/service/DefaultPrometheusMetrics.java b/src/main/java/org/jenkinsci/plugins/prometheus/service/DefaultPrometheusMetrics.java
index 1cf59d43a..a7941ea84 100644
--- a/src/main/java/org/jenkinsci/plugins/prometheus/service/DefaultPrometheusMetrics.java
+++ b/src/main/java/org/jenkinsci/plugins/prometheus/service/DefaultPrometheusMetrics.java
@@ -4,12 +4,14 @@
 import hudson.ExtensionList;
 import hudson.init.InitMilestone;
 import hudson.init.Initializer;
+import hudson.triggers.SafeTimerTask;
 import io.prometheus.client.Collector;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.dropwizard.DropwizardExports;
 import io.prometheus.client.exporter.common.TextFormat;
 import io.prometheus.client.hotspot.DefaultExports;
 import jenkins.metrics.api.Metrics;
+import jenkins.util.Timer;
 import org.jenkinsci.plugins.prometheus.CodeCoverageCollector;
 import org.jenkinsci.plugins.prometheus.DiskUsageCollector;
 import org.jenkinsci.plugins.prometheus.ExecutorCollector;
@@ -24,6 +26,7 @@
 
 import java.io.IOException;
 import java.io.StringWriter;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
 public class DefaultPrometheusMetrics implements PrometheusMetrics {
@@ -50,29 +53,41 @@ public static synchronized DefaultPrometheusMetrics get() {
     }
 
     @Restricted(NoExternalUse.class)
-    private void registerCollector(@NonNull Collector collector) {
-        collectorRegistry.register(collector);
-        logger.debug(String.format("Collector %s registered", collector.getClass().getName()));
+    private void initRegistry() {
+        this.collectorRegistry.clear();
+        DefaultExports.register(this.collectorRegistry);
     }
 
     @Restricted(NoExternalUse.class)
-    @Initializer(after = InitMilestone.EXTENSIONS_AUGMENTED, before = InitMilestone.JOB_LOADED)
-    public static void registerCollectors() {
-        DefaultPrometheusMetrics instance = get();
-        instance.registerCollector(new JenkinsStatusCollector());
-        instance.registerCollector(new DropwizardExports(Metrics.metricRegistry(), new JenkinsNodeBuildsSampleBuilder()));
-        instance.registerCollector(new DiskUsageCollector());
-        instance.registerCollector(new ExecutorCollector());
+    private void registerCollector(@NonNull Collector collector) {
+        collectorRegistry.register(collector);
+        logger.debug(String.format("Collector %s registered", collector.getClass().getName()));
     }
 
     @Restricted(NoExternalUse.class)
     @Initializer(after = InitMilestone.JOB_LOADED, before = InitMilestone.JOB_CONFIG_ADAPTED)
-    public static void registerJobCollectors() {
-        DefaultPrometheusMetrics instance = get();
-        instance.registerCollector(new JobCollector());
-        instance.registerCollector(new CodeCoverageCollector());
-        // other collectors from other plugins
-        ExtensionList.lookup(Collector.class).forEach(instance::registerCollector);
+    public static void registerCollectors() {
+        Timer.get()
+            .schedule(
+                new SafeTimerTask() {
+                    @Override
+                    public void doRun() throws Exception {
+                        logger.debug("Initializing Collectors");
+                        DefaultPrometheusMetrics instance = get();
+                        instance.initRegistry();
+                        instance.registerCollector(new JenkinsStatusCollector());
+                        instance.registerCollector(new DropwizardExports(Metrics.metricRegistry(), new JenkinsNodeBuildsSampleBuilder()));
+                        instance.registerCollector(new DiskUsageCollector());
+                        instance.registerCollector(new ExecutorCollector());
+                        instance.registerCollector(new JobCollector());
+                        instance.registerCollector(new CodeCoverageCollector());
+                        // other collectors from other plugins
+                        ExtensionList.lookup(Collector.class).forEach(instance::registerCollector);
+                        logger.debug("Finished initializing Collectors");
+                    }
+                },
+                1,
+                TimeUnit.SECONDS);
     }
 
     @Override