Fix integration with the CloudBees Simple Disk Usage Plugin

Author: cyrille-leclerc

…uter/DiskUsageMonitoringInitializer.java …init/DiskUsageMonitoringInitializer.javasrc/main/java/io/jenkins/plugins/opentelemetry/computer/DiskUsageMonitoringInitializer.java renamed to src/main/java/io/jenkins/plugins/opentelemetry/init/DiskUsageMonitoringInitializer.java src/main/java/io/jenkins/plugins/opentelemetry/computer/DiskUsageMonitoringInitializer.java renamed to src/main/java/io/jenkins/plugins/opentelemetry/init/DiskUsageMonitoringInitializer.java

@@ -3,62 +3,70 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-package io.jenkins.plugins.opentelemetry.computer;
+package io.jenkins.plugins.opentelemetry.init;
 
 import com.cloudbees.simplediskusage.DiskItem;
+import com.cloudbees.simplediskusage.QuickDiskUsageInitializer;
 import com.cloudbees.simplediskusage.QuickDiskUsagePlugin;
 import hudson.Extension;
-import hudson.ExtensionPoint;
 import hudson.init.InitMilestone;
 import hudson.init.Initializer;
-import hudson.slaves.ComputerListener;
 import io.jenkins.plugins.opentelemetry.OpenTelemetrySdkProvider;
-import io.jenkins.plugins.opentelemetry.init.OpenTelemetryPluginAbstractInitializer;
 import io.jenkins.plugins.opentelemetry.semconv.JenkinsSemanticMetrics;
 import io.opentelemetry.api.metrics.Meter;
 import jenkins.YesNoMaybe;
 import jenkins.model.Jenkins;
 
 import javax.annotation.Nonnull;
-import javax.annotation.PostConstruct;
 import javax.inject.Inject;
 import java.io.IOException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
 /**
- * Note: we extend {@link ComputerListener} instead of a plain {@link ExtensionPoint} because simple ExtensionPoint don't get automatically loaded by Jenkins
- * There may be a better API to do this.
+ * Capture disk usage metrics relying on the {@link QuickDiskUsagePlugin}
  */
-@Extension(dynamicLoadable = YesNoMaybe.MAYBE, optional = true)
+@Extension(dynamicLoadable = YesNoMaybe.YES, optional = true)
 public class DiskUsageMonitoringInitializer {
 
     private final static Logger LOGGER = Logger.getLogger(DiskUsageMonitoringInitializer.class.getName());
 
     protected Meter meter;
 
+    /**
+     * Don't inject the `quickDiskUsagePlugin` using @{@link  Inject} because the injected instance is not the right once.
+     * Lazy load it using {@link Jenkins#getPlugin(Class)}.
+     */
     protected QuickDiskUsagePlugin quickDiskUsagePlugin;
 
-    @Initializer(after = InitMilestone.JOB_LOADED)
+    /**
+     * TODO ensure initialized after {@link QuickDiskUsageInitializer#initialize()} has been invoked by Jenkins
+     * lifecycle before {@link io.opentelemetry.api.metrics.ObservableLongMeasurement#observe(long)} is invoked
+     */
+    @Initializer(after = InitMilestone.JOB_CONFIG_ADAPTED)
     public void initialize() {
-        if (quickDiskUsagePlugin == null) {
-            LOGGER.log(Level.WARNING, () -> "Plugin 'disk-usage' not loaded, don't start monitoring Jenkins controller disk usage");
-        } else {
             meter.gaugeBuilder(JenkinsSemanticMetrics.JENKINS_DISK_USAGE_BYTES)
                 .ofLongs()
                 .setDescription("Disk usage of first level folder in JENKINS_HOME.")
                 .setUnit("byte")
-                .buildWithCallback(valueObserver -> valueObserver.observe(calculateDiskUsageInBytes(quickDiskUsagePlugin)));
+                .buildWithCallback(valueObserver -> valueObserver.observe(calculateDiskUsageInBytes()));
             LOGGER.log(Level.FINE, () -> "Start monitoring Jenkins controller disk usage");
+    }
+    private long calculateDiskUsageInBytes() {
+        if (this.quickDiskUsagePlugin == null) {
+            Jenkins jenkins = Jenkins.get();
+            QuickDiskUsagePlugin quickDiskUsagePlugin = jenkins.getPlugin(QuickDiskUsagePlugin.class);
+            if (quickDiskUsagePlugin == null) return 0l;
+            this.quickDiskUsagePlugin = quickDiskUsagePlugin;
         }
+        return calculateDiskUsageInBytes(quickDiskUsagePlugin);
     }
-
     private long calculateDiskUsageInBytes(@Nonnull QuickDiskUsagePlugin diskUsagePlugin) {
         LOGGER.log(Level.FINE, "calculateDiskUsageInBytes");
         try {
             DiskItem disk = diskUsagePlugin.getDirectoriesUsages()
                     .stream()
-                    .filter(x -> x.getDisplayName().equals("JENKINS_HOME"))
+                    .filter(diskItem -> diskItem.getDisplayName().equals("JENKINS_HOME"))
                     .findFirst()
                     .orElse(null);
             if (disk == null) {
@@ -72,11 +80,6 @@ private long calculateDiskUsageInBytes(@Nonnull QuickDiskUsagePlugin diskUsagePl
         }
     }
 
-    @Inject
-    public void setQuickDiskUsagePlugin(QuickDiskUsagePlugin quickDiskUsagePlugin) {
-        this.quickDiskUsagePlugin = quickDiskUsagePlugin;
-    }
-
     /**
      * Jenkins doesn't support {@link com.google.inject.Provides} so we manually wire dependencies :-(
      */