feat: runtime info for health probes (#1594)

Author: csviri

docs/documentation/features.md

@@ -699,6 +699,18 @@ leader left off should one of them become elected leader.
 See sample configuration in the [E2E test](https://github.com/java-operator-sdk/java-operator-sdk/blob/8865302ac0346ee31f2d7b348997ec2913d5922b/sample-operators/leader-election/src/main/java/io/javaoperatorsdk/operator/sample/LeaderElectionTestOperator.java#L21-L23)
 .
 
+## Runtime Info
+
+[RuntimeInfo](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/RuntimeInfo.java#L16-L16) 
+is used mainly to check the actual health of event sources. Based on this information it is easy to implement custom 
+liveness probes.
+
+[stopOnInformerErrorDuringStartup](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationService.java#L168-L168)
+setting, where this flag usually needs to be set to false, in order to control the exact liveness properties.
+
+See also an example implementation in the 
+[WebPage sample](https://github.com/java-operator-sdk/java-operator-sdk/blob/3e2e7c4c834ef1c409d636156b988125744ca911/sample-operators/webpage/src/main/java/io/javaoperatorsdk/operator/sample/WebPageOperator.java#L38-L43)
+
 ## Monitoring with Micrometer
 
 ## Automatic Generation of CRDs

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/Operator.java

@@ -90,12 +90,11 @@ public KubernetesClient getKubernetesClient() {
    * where there is no obvious entrypoint to the application which can trigger the injection process
    * and start the cluster monitoring processes.
    */
-  public void start() {
+  public synchronized void start() {
     try {
       if (started) {
         return;
       }
-      started = true;
       controllerManager.shouldStart();
       final var version = ConfigurationServiceProvider.instance().getVersion();
       log.info(
@@ -111,6 +110,7 @@ public void start() {
       // the leader election would start subsequently the processor if on
       controllerManager.start(!leaderElectionManager.isLeaderElectionEnabled());
       leaderElectionManager.start();
+      started = true;
     } catch (Exception e) {
       log.error("Error starting operator", e);
       stop();
@@ -217,4 +217,11 @@ public int getRegisteredControllersNumber() {
     return controllerManager.size();
   }
 
+  public RuntimeInfo getRuntimeInfo() {
+    return new RuntimeInfo(this);
+  }
+
+  boolean isStarted() {
+    return started;
+  }
 }

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/RegisteredController.java

@@ -3,7 +3,12 @@
 import io.fabric8.kubernetes.api.model.HasMetadata;
 import io.javaoperatorsdk.operator.api.config.ControllerConfiguration;
 import io.javaoperatorsdk.operator.api.config.NamespaceChangeable;
+import io.javaoperatorsdk.operator.health.ControllerHealthInfo;
 
 public interface RegisteredController<P extends HasMetadata> extends NamespaceChangeable {
+
   ControllerConfiguration<P> getConfiguration();
+
+  ControllerHealthInfo getControllerHealthInfo();
+
 }

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/RuntimeInfo.java

@@ -0,0 +1,81 @@
+package io.javaoperatorsdk.operator;
+
+import java.util.*;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.javaoperatorsdk.operator.health.EventSourceHealthIndicator;
+import io.javaoperatorsdk.operator.health.InformerWrappingEventSourceHealthIndicator;
+
+/**
+ * RuntimeInfo in general is available when operator is fully started. You can use "isStarted" to
+ * check that.
+ */
+@SuppressWarnings("rawtypes")
+public class RuntimeInfo {
+
+  private static final Logger log = LoggerFactory.getLogger(RuntimeInfo.class);
+
+  private final Set<RegisteredController> registeredControllers;
+  private final Operator operator;
+
+  public RuntimeInfo(Operator operator) {
+    this.registeredControllers = operator.getRegisteredControllers();
+    this.operator = operator;
+  }
+
+  public boolean isStarted() {
+    return operator.isStarted();
+  }
+
+  public Set<RegisteredController> getRegisteredControllers() {
+    checkIfStarted();
+    return registeredControllers;
+  }
+
+  private void checkIfStarted() {
+    if (!isStarted()) {
+      log.warn(
+          "Operator not started yet while accessing runtime info, this might lead to an unreliable behavior");
+    }
+  }
+
+  public boolean allEventSourcesAreHealthy() {
+    checkIfStarted();
+    return registeredControllers.stream()
+        .filter(rc -> !rc.getControllerHealthInfo().unhealthyEventSources().isEmpty())
+        .findFirst().isEmpty();
+  }
+
+  /**
+   * @return Aggregated Map with controller related event sources.
+   */
+
+  public Map<String, Map<String, EventSourceHealthIndicator>> unhealthyEventSources() {
+    checkIfStarted();
+    Map<String, Map<String, EventSourceHealthIndicator>> res = new HashMap<>();
+    for (var rc : registeredControllers) {
+      res.put(rc.getConfiguration().getName(),
+          rc.getControllerHealthInfo().unhealthyEventSources());
+    }
+    return res;
+  }
+
+  /**
+   * @return Aggregated Map with controller related event sources that wraps an informer. Thus,
+   *         either a
+   *         {@link io.javaoperatorsdk.operator.processing.event.source.controller.ControllerResourceEventSource}
+   *         or an
+   *         {@link io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource}.
+   */
+  public Map<String, Map<String, InformerWrappingEventSourceHealthIndicator>> unhealthyInformerWrappingEventSourceHealthIndicator() {
+    checkIfStarted();
+    Map<String, Map<String, InformerWrappingEventSourceHealthIndicator>> res = new HashMap<>();
+    for (var rc : registeredControllers) {
+      res.put(rc.getConfiguration().getName(), rc.getControllerHealthInfo()
+          .unhealthyInformerEventSourceHealthIndicators());
+    }
+    return res;
+  }
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/health/ControllerHealthInfo.java

@@ -0,0 +1,50 @@
+package io.javaoperatorsdk.operator.health;
+
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import io.javaoperatorsdk.operator.processing.event.EventSourceManager;
+
+@SuppressWarnings("rawtypes")
+public class ControllerHealthInfo {
+
+  private EventSourceManager<?> eventSourceManager;
+
+  public ControllerHealthInfo(EventSourceManager eventSourceManager) {
+    this.eventSourceManager = eventSourceManager;
+  }
+
+  public Map<String, EventSourceHealthIndicator> eventSourceHealthIndicators() {
+    return eventSourceManager.allEventSources().entrySet().stream()
+        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+  }
+
+  public Map<String, EventSourceHealthIndicator> unhealthyEventSources() {
+    return eventSourceManager.allEventSources().entrySet().stream()
+        .filter(e -> e.getValue().getStatus() == Status.UNHEALTHY)
+        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+  }
+
+  public Map<String, InformerWrappingEventSourceHealthIndicator> informerEventSourceHealthIndicators() {
+    return eventSourceManager.allEventSources().entrySet().stream()
+        .filter(e -> e.getValue() instanceof InformerWrappingEventSourceHealthIndicator)
+        .collect(Collectors.toMap(Map.Entry::getKey,
+            e -> (InformerWrappingEventSourceHealthIndicator) e.getValue()));
+
+  }
+
+  /**
+   * @return Map with event sources that wraps an informer. Thus, either a
+   *         {@link io.javaoperatorsdk.operator.processing.event.source.controller.ControllerResourceEventSource}
+   *         or an
+   *         {@link io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource}.
+   */
+  public Map<String, InformerWrappingEventSourceHealthIndicator> unhealthyInformerEventSourceHealthIndicators() {
+    return eventSourceManager.allEventSources().entrySet().stream()
+        .filter(e -> e.getValue().getStatus() == Status.UNHEALTHY)
+        .filter(e -> e.getValue() instanceof InformerWrappingEventSourceHealthIndicator)
+        .collect(Collectors.toMap(Map.Entry::getKey,
+            e -> (InformerWrappingEventSourceHealthIndicator) e.getValue()));
+  }
+
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/health/EventSourceHealthIndicator.java

@@ -0,0 +1,6 @@
+package io.javaoperatorsdk.operator.health;
+
+public interface EventSourceHealthIndicator {
+
+  Status getStatus();
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/health/InformerHealthIndicator.java

@@ -0,0 +1,17 @@
+package io.javaoperatorsdk.operator.health;
+
+public interface InformerHealthIndicator extends EventSourceHealthIndicator {
+
+  boolean hasSynced();
+
+  boolean isWatching();
+
+  boolean isRunning();
+
+  @Override
+  default Status getStatus() {
+    return isRunning() && hasSynced() && isWatching() ? Status.HEALTHY : Status.UNHEALTHY;
+  }
+
+  String getTargetNamespace();
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/health/InformerWrappingEventSourceHealthIndicator.java

@@ -0,0 +1,22 @@
+package io.javaoperatorsdk.operator.health;
+
+import java.util.Map;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.api.config.ResourceConfiguration;
+
+public interface InformerWrappingEventSourceHealthIndicator<R extends HasMetadata>
+    extends EventSourceHealthIndicator {
+
+  Map<String, InformerHealthIndicator> informerHealthIndicators();
+
+  @Override
+  default Status getStatus() {
+    var nonUp = informerHealthIndicators().values().stream()
+        .filter(i -> i.getStatus() != Status.HEALTHY).findAny();
+
+    return nonUp.isPresent() ? Status.UNHEALTHY : Status.HEALTHY;
+  }
+
+  ResourceConfiguration<R> getInformerConfiguration();
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/health/Status.java

@@ -0,0 +1,11 @@
+package io.javaoperatorsdk.operator.health;
+
+public enum Status {
+
+  HEALTHY, UNHEALTHY,
+  /**
+   * For event sources where it cannot be determined if it is healthy ot not.
+   */
+  UNKNOWN
+
+}

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/Controller.java

@@ -39,6 +39,7 @@
 import io.javaoperatorsdk.operator.api.reconciler.dependent.EventSourceProvider;
 import io.javaoperatorsdk.operator.api.reconciler.dependent.EventSourceReferencer;
 import io.javaoperatorsdk.operator.api.reconciler.dependent.managed.DefaultManagedDependentResourceContext;
+import io.javaoperatorsdk.operator.health.ControllerHealthInfo;
 import io.javaoperatorsdk.operator.processing.dependent.workflow.ManagedWorkflow;
 import io.javaoperatorsdk.operator.processing.dependent.workflow.WorkflowCleanupResult;
 import io.javaoperatorsdk.operator.processing.event.EventProcessor;
@@ -67,6 +68,7 @@ public class Controller<P extends HasMetadata>
 
   private final GroupVersionKind associatedGVK;
   private final EventProcessor<P> eventProcessor;
+  private final ControllerHealthInfo controllerHealthInfo;
 
   public Controller(Reconciler<P> reconciler,
       ControllerConfiguration<P> configuration,
@@ -87,6 +89,7 @@ public Controller(Reconciler<P> reconciler,
     eventSourceManager = new EventSourceManager<>(this);
     eventProcessor = new EventProcessor<>(eventSourceManager);
     eventSourceManager.postProcessDefaultEventSourcesAfterProcessorInitializer();
+    controllerHealthInfo = new ControllerHealthInfo(eventSourceManager);
 
     final var context = new EventSourceContext<>(
         eventSourceManager.getControllerResourceEventSource(), configuration, kubernetesClient);
@@ -289,6 +292,11 @@ public ControllerConfiguration<P> getConfiguration() {
     return configuration;
   }
 
+  @Override
+  public ControllerHealthInfo getControllerHealthInfo() {
+    return controllerHealthInfo;
+  }
+
   public KubernetesClient getClient() {
     return kubernetesClient;
   }