Fix startup order

src/main/java/org/jenkinsci/plugins/prometheus/config/PrometheusConfiguration.java

@@ -1,6 +1,7 @@
 package org.jenkinsci.plugins.prometheus.config;
 
 import hudson.Extension;
+import hudson.ExtensionList;
 import hudson.util.FormValidation;
 import jenkins.YesNoMaybe;
 import jenkins.model.GlobalConfiguration;
@@ -76,7 +77,7 @@ public PrometheusConfiguration() {
     }
 
     public static PrometheusConfiguration get() {
-        return (PrometheusConfiguration) Jenkins.get().getDescriptor(PrometheusConfiguration.class);
+        return ExtensionList.lookupSingleton(PrometheusConfiguration.class);
     }
 
     @Override

src/main/java/org/jenkinsci/plugins/prometheus/config/disabledmetrics/MetricStatusChecker.java

@@ -18,10 +18,6 @@ public class MetricStatusChecker {
     public static boolean isEnabled(String metricName) {
 
         PrometheusConfiguration configuration = PrometheusConfiguration.get();
-        if (configuration == null) {
-            LOGGER.warn("Cannot check if metric is enabled. Unable to get PrometheusConfiguration");
-            return true;
-        }
 
         DisabledMetricConfig disabledMetricConfig = configuration.getDisabledMetricConfig();
         if (disabledMetricConfig == null) {

src/main/java/org/jenkinsci/plugins/prometheus/init/Initializers.java

@@ -0,0 +1,26 @@
+package org.jenkinsci.plugins.prometheus.init;
+
+import hudson.ExtensionList;
+import hudson.init.InitMilestone;
+import hudson.init.Initializer;
+import org.jenkinsci.plugins.prometheus.service.PrometheusMetrics;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+public class Initializers {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(Initializers.class.getName());
+
+    @Initializer(before = InitMilestone.COMPLETED)
+    public static void initializePrometheusMetrics() {
+        LOGGER.debug("Initializing Prometheus Plugin");
+        try {
+            PrometheusMetrics prometheusMetrics = ExtensionList.lookupSingleton(PrometheusMetrics.class);
+            prometheusMetrics.initialize();
+        } catch (IllegalStateException e) {
+            LOGGER.error("Unable to load Prometheus Plugin. Collecting Metrics won't work", e);
+        }
+    }
+
+}

src/main/java/org/jenkinsci/plugins/prometheus/service/DefaultPrometheusMetrics.java

@@ -2,8 +2,6 @@
 
 import hudson.Extension;
 import hudson.ExtensionList;
-import hudson.init.InitMilestone;
-import hudson.init.Initializer;
 import io.prometheus.client.Collector;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.dropwizard.DropwizardExports;
@@ -30,34 +28,13 @@ public class DefaultPrometheusMetrics implements PrometheusMetrics {
 
     private volatile boolean initialized = false;
     private volatile boolean initializing = false;
-    private final CollectorRegistry collectorRegistry;
+    private CollectorRegistry collectorRegistry;
     private final AtomicReference<String> cachedMetrics;
 
     public DefaultPrometheusMetrics() {
-        this.collectorRegistry = CollectorRegistry.defaultRegistry;
         this.cachedMetrics = new AtomicReference<>("");
     }
 
-    @Initializer(after = InitMilestone.JOB_LOADED)
-    public void registerCollectors() {
-        if (!initialized && !initializing) {
-            initializing = true;
-            LOGGER.debug("Initializing...");
-            collectorRegistry.register(new JobCollector());
-            collectorRegistry.register(new JenkinsStatusCollector());
-            collectorRegistry.register(
-                    new DropwizardExports(Metrics.metricRegistry(), new JenkinsNodeBuildsSampleBuilder()));
-            collectorRegistry.register(new DiskUsageCollector());
-            collectorRegistry.register(new ExecutorCollector());
-            collectorRegistry.register(new CodeCoverageCollector());
-            // other collectors from other plugins
-            ExtensionList.lookup(Collector.class).forEach(collectorRegistry::register);
-            DefaultExports.initialize();
-            initialized = true;
-            initializing = false;
-        }
-    }
-
     @Override
     public String getMetrics() {
         return cachedMetrics.get();
@@ -76,4 +53,25 @@ public void collectMetrics() {
             LOGGER.debug("Unable to collect metrics");
         }
     }
+
+    @Override
+    public void initialize() {
+        if (!initialized && !initializing) {
+            this.collectorRegistry = CollectorRegistry.defaultRegistry;
+            initializing = true;
+            LOGGER.debug("Initializing...");
+            collectorRegistry.register(new JobCollector());
+            collectorRegistry.register(new JenkinsStatusCollector());
+            collectorRegistry.register(
+                    new DropwizardExports(Metrics.metricRegistry(), new JenkinsNodeBuildsSampleBuilder()));
+            collectorRegistry.register(new DiskUsageCollector());
+            collectorRegistry.register(new ExecutorCollector());
+            collectorRegistry.register(new CodeCoverageCollector());
+            // other collectors from other plugins
+            ExtensionList.lookup(Collector.class).forEach(collectorRegistry::register);
+            DefaultExports.initialize();
+            initialized = true;
+            initializing = false;
+        }
+    }
 }

src/main/java/org/jenkinsci/plugins/prometheus/service/PrometheusMetrics.java

@@ -8,4 +8,6 @@ public interface PrometheusMetrics extends ExtensionPoint {
 
     void collectMetrics();
 
+    void initialize();
+
 }

src/test/java/org/jenkinsci/plugins/prometheus/config/disabledmetrics/MetricStatusCheckerTest.java

@@ -15,26 +15,6 @@
 
 public class MetricStatusCheckerTest {
 
-    @Test
-    void testNoConfigWontFail() {
-        Jenkins jenkins = mock(Jenkins.class);
-
-        PrometheusConfiguration mockedConfig = mock(PrometheusConfiguration.class);
-        String namespace = "TestNamespace";
-
-        when(mockedConfig.getDefaultNamespace()).thenReturn(namespace);
-        when(mockedConfig.isCollectNodeStatus()).thenReturn(false);
-
-        try (MockedStatic<Jenkins> jenkinsStatic = mockStatic(Jenkins.class);
-             MockedStatic<PrometheusConfiguration> configStatic = mockStatic(PrometheusConfiguration.class)) {
-            jenkinsStatic.when(Jenkins::get).thenReturn(jenkins);
-            configStatic.when(PrometheusConfiguration::get).thenReturn(null);
-
-            boolean enabled = MetricStatusChecker.isEnabled("some_metric");
-            Assertions.assertTrue(enabled);
-        }
-    }
-
     @Test
     void testNoDisabledMetricConfigWontFail() {
         Jenkins jenkins = mock(Jenkins.class);

src/test/java/org/jenkinsci/plugins/prometheus/rest/PrometheusActionTest.java

@@ -34,18 +34,22 @@ public class PrometheusActionTest {
     @Mock
     private PrometheusConfiguration configuration;
 
+    private MockedStatic<ExtensionList> extensionListStatic;
     private MockedStatic<Jenkins> jenkinsStatic;
 
     @BeforeEach
     public void setUp() {
         jenkinsStatic = mockStatic(Jenkins.class);
         jenkinsStatic.when(Jenkins::get).thenReturn(jenkins);
-        when(jenkins.getDescriptor(PrometheusConfiguration.class)).thenReturn(configuration);
+
         when(configuration.getAdditionalPath()).thenReturn("prometheus");
+        extensionListStatic = mockStatic(ExtensionList.class);
+        extensionListStatic.when(() -> ExtensionList.lookupSingleton(PrometheusConfiguration.class)).thenReturn(configuration);
     }
 
     @AfterEach
     public void tearDown() {
+        extensionListStatic.close();
         jenkinsStatic.close();
     }
 
@@ -92,23 +96,23 @@ public void shouldReturnMetrics() throws IOException, ServletException {
         PrometheusMetrics prometheusMetrics = mock(PrometheusMetrics.class);
         String responseBody = "testMetric";
         when(prometheusMetrics.getMetrics()).thenReturn(responseBody);
-        try (MockedStatic<ExtensionList> extensionListMockedStatic = mockStatic(ExtensionList.class)) {
-            extensionListMockedStatic.when(() -> ExtensionList.lookupSingleton(PrometheusMetrics.class)).thenReturn(prometheusMetrics);
-            StaplerRequest request = mock(StaplerRequest.class);
-            String url = "prometheus";
-            when(request.getRestOfPath()).thenReturn(url);
-
-            // when
-            HttpResponse actual = action.doDynamic(request);
-
-            // then
-            AssertStaplerResponse.from(actual)
-                    .call()
-                    .assertHttpStatus(HTTP_OK)
-                    .assertContentType(TextFormat.CONTENT_TYPE_004)
-                    .assertHttpHeader("Cache-Control", "must-revalidate,no-cache,no-store")
-                    .assertBody(responseBody);
-        }
+
+        extensionListStatic.when(() -> ExtensionList.lookupSingleton(PrometheusMetrics.class)).thenReturn(prometheusMetrics);
+        StaplerRequest request = mock(StaplerRequest.class);
+        String url = "prometheus";
+        when(request.getRestOfPath()).thenReturn(url);
+
+        // when
+        HttpResponse actual = action.doDynamic(request);
+
+        // then
+        AssertStaplerResponse.from(actual)
+                .call()
+                .assertHttpStatus(HTTP_OK)
+                .assertContentType(TextFormat.CONTENT_TYPE_004)
+                .assertHttpHeader("Cache-Control", "must-revalidate,no-cache,no-store")
+                .assertBody(responseBody);
+
 
     }
 

src/test/java/org/jenkinsci/plugins/prometheus/service/PrometheusAsyncWorkerTest.java

@@ -67,5 +67,9 @@ public void collectMetrics() {
             cachedMetrics.set(metrics);
         }
 
+        @Override
+        public void initialize() {
+
+        }
     }
 }