Observe instantaneous events

micrometer-core/src/main/java/io/micrometer/core/instrument/observation/TimerObservationHandler.java → micrometer-core/src/main/java/io/micrometer/core/instrument/observation/DefaultMeterObservationHandler.java

@@ -21,7 +21,7 @@
 import java.util.stream.Collectors;
 
 /**
- * Handler for {@link Timer.Sample}.
+ * Handler for {@link Timer.Sample} and {@link Counter}
  *
  * WARNING: Since the {@link LongTaskTimer} needs to be created in the {@code onStart}
  * method, it can only contain tags that are available by that time. This means that if
@@ -36,11 +36,11 @@
  * @author Jonatan Ivanov
  * @since 1.10.0
  */
-public class TimerObservationHandler implements MeterObservationHandler<Observation.Context> {
+public class DefaultMeterObservationHandler implements MeterObservationHandler<Observation.Context> {
 
     private final MeterRegistry meterRegistry;
 
-    public TimerObservationHandler(MeterRegistry meterRegistry) {
+    public DefaultMeterObservationHandler(MeterRegistry meterRegistry) {
         this.meterRegistry = meterRegistry;
     }
 
@@ -65,8 +65,8 @@ public void onStop(Observation.Context context) {
     }
 
     @Override
-    public boolean supportsContext(Observation.Context context) {
-        return true;
+    public void onEvent(Observation.Event event, Observation.Context context) {
+        Counter.builder(event.getName()).tags(createTags(context)).register(meterRegistry).increment();
     }
 
     private Tags createErrorTags(Observation.Context context) {

micrometer-core/src/main/java/io/micrometer/core/instrument/observation/MeterObservationHandler.java

@@ -27,4 +27,9 @@
  */
 public interface MeterObservationHandler<T extends Observation.Context> extends ObservationHandler<T> {
 
+    @Override
+    default boolean supportsContext(Observation.Context context) {
+        return true;
+    }
+
 }

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/okhttp3/OkHttpObservationInterceptorTest.java

@@ -21,7 +21,7 @@
 import io.micrometer.common.KeyValues;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.MockClock;
-import io.micrometer.core.instrument.observation.TimerObservationHandler;
+import io.micrometer.core.instrument.observation.DefaultMeterObservationHandler;
 import io.micrometer.core.instrument.simple.SimpleConfig;
 import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
 import io.micrometer.observation.Observation;
@@ -76,7 +76,7 @@ private OkHttpObservationInterceptor.Builder defaultInterceptorBuilder() {
     @BeforeEach
     void setup() {
         observationRegistry.observationConfig().observationHandler(testHandler);
-        observationRegistry.observationConfig().observationHandler(new TimerObservationHandler(registry));
+        observationRegistry.observationConfig().observationHandler(new DefaultMeterObservationHandler(registry));
         observationRegistry.observationConfig().observationHandler(new PropagatingHandler());
     }
 

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/AnyContextObservationHandlerCompatibilityKit.java

@@ -41,6 +41,8 @@ void handlerSupportsAnyContext() {
         assertThatCode(() -> handler.onStart(testContext)).doesNotThrowAnyException();
         assertThatCode(() -> handler.onStop(testContext)).doesNotThrowAnyException();
         assertThatCode(() -> handler.onError(testContext)).doesNotThrowAnyException();
+        assertThatCode(() -> handler.onEvent(new Observation.Event("testEvent"), testContext))
+                .doesNotThrowAnyException();
         assertThatCode(() -> handler.onScopeOpened(testContext)).doesNotThrowAnyException();
         assertThatCode(() -> handler.supportsContext(testContext)).doesNotThrowAnyException();
         assertThat(handler.supportsContext(testContext)).as("Handler supports any context").isTrue();

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/ConcreteContextObservationHandlerCompatibilityKit.java

@@ -58,6 +58,7 @@ void handlerSupportsConcreteContextForHandlerMethods() {
         assertThatCode(() -> handler.onStart(context())).doesNotThrowAnyException();
         assertThatCode(() -> handler.onStop(context())).doesNotThrowAnyException();
         assertThatCode(() -> handler.onError(context())).doesNotThrowAnyException();
+        assertThatCode(() -> handler.onEvent(new Observation.Event("testEvent"), context())).doesNotThrowAnyException();
         assertThatCode(() -> handler.onScopeOpened(context())).doesNotThrowAnyException();
     }
 

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/NullContextObservationHandlerCompatibilityKit.java

@@ -56,6 +56,7 @@ void handlerSupportsNullContext() {
         assertThatCode(() -> handler.onStart(null)).doesNotThrowAnyException();
         assertThatCode(() -> handler.onStop(null)).doesNotThrowAnyException();
         assertThatCode(() -> handler.onError(null)).doesNotThrowAnyException();
+        assertThatCode(() -> handler.onEvent(null, null)).doesNotThrowAnyException();
         assertThatCode(() -> handler.onScopeOpened(null)).doesNotThrowAnyException();
         assertThatCode(() -> handler.supportsContext(null)).doesNotThrowAnyException();
         assertThat(handler.supportsContext(null)).as("Handler supports null context").isTrue();

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/ObservationRegistryCompatibilityKit.java

@@ -17,6 +17,7 @@
 
 import io.micrometer.common.KeyValue;
 import io.micrometer.common.KeyValues;
+import io.micrometer.common.lang.Nullable;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationHandler;
 import io.micrometer.observation.ObservationRegistry;
@@ -80,6 +81,10 @@ void observeWithHandlers() {
             inOrder.verify(handler).onScopeOpened(isA(Observation.Context.class));
             assertThat(scope.getCurrentObservation()).isSameAs(observation);
 
+            Observation.Event event = new Observation.Event("testEvent", "event for testing");
+            observation.event(event);
+            inOrder.verify(handler).onEvent(same(event), isA(Observation.Context.class));
+
             Throwable exception = new IOException("simulated");
             observation.error(exception);
             inOrder.verify(handler).onError(isA(Observation.Context.class));
@@ -455,10 +460,6 @@ public boolean supportsContext(Observation.Context context) {
             return context instanceof TestContext;
         }
 
-        public String getId() {
-            return this.id;
-        }
-
     }
 
     static class UnsupportedKeyValuesProvider implements Observation.GlobalKeyValuesProvider<Observation.Context> {
@@ -490,6 +491,7 @@ static class AssertingHandler implements ObservationHandler<Observation.Context>
 
         private boolean stopped = false;
 
+        @Nullable
         private Observation.Context context = null;
 
         @Override

micrometer-observation-test/src/test/java/io/micrometer/observation/tck/AnyContextObservationHandlerCompatibilityKitTests.java

@@ -31,6 +31,10 @@ public void onStart(Observation.Context context) {
             public void onError(Observation.Context context) {
             }
 
+            @Override
+            public void onEvent(Observation.Event event, Observation.Context context) {
+            }
+
             @Override
             public void onScopeOpened(Observation.Context context) {
             }

micrometer-observation-test/src/test/java/io/micrometer/observation/tck/ConcreteContextObservationHandlerCompatibilityKitTests.java

@@ -32,6 +32,10 @@ public void onStart(Observation.Context context) {
             public void onError(Observation.Context context) {
             }
 
+            @Override
+            public void onEvent(Observation.Event event, Observation.Context context) {
+            }
+
             @Override
             public void onScopeOpened(Observation.Context context) {
 

micrometer-observation-test/src/test/java/io/micrometer/observation/tck/NullContextObservationHandlerCompatibilityKitTests.java

@@ -31,6 +31,10 @@ public void onStart(Observation.Context context) {
             public void onError(Observation.Context context) {
             }
 
+            @Override
+            public void onEvent(Observation.Event event, Observation.Context context) {
+            }
+
             @Override
             public void onScopeOpened(Observation.Context context) {
             }

micrometer-observation/src/main/java/io/micrometer/observation/NoopObservation.java

@@ -78,6 +78,11 @@ public Observation error(Throwable error) {
         return this;
     }
 
+    @Override
+    public Observation event(Event event) {
+        return this;
+    }
+
     @Override
     public Observation start() {
         return this;

micrometer-observation/src/main/java/io/micrometer/observation/Observation.java

@@ -59,7 +59,7 @@ public interface Observation {
      * @param registry observation registry
      * @return started observation
      */
-    static Observation start(String name, @Nullable ObservationRegistry registry) {
+    static Observation start(String name, ObservationRegistry registry) {
         return start(name, null, registry);
     }
 
@@ -322,12 +322,19 @@ default boolean isNoop() {
     Observation keyValuesProvider(KeyValuesProvider<?> keyValuesProvider);
 
     /**
-     * Sets an error.
+     * Signals an error.
      * @param error error
      * @return this
      */
     Observation error(Throwable error);
 
+    /**
+     * Signals an arbitrary {@link Event}.
+     * @param event event
+     * @return this
+     */
+    Observation event(Event event);
+
     /**
      * Starts the observation. Remember to call this method, otherwise timing calculations
      * will not take place.
@@ -576,6 +583,7 @@ class Context implements ContextView {
 
         private String name;
 
+        @Nullable
         private String contextualName;
 
         @Nullable
@@ -826,6 +834,56 @@ private String toString(Map<Object, Object> map) {
 
     }
 
+    /**
+     * An arbitrary event that you can extend and signal during an {@link Observation}.
+     * This helps you to tell to the {@link ObservationHandler} that something happened.
+     * If you want to signal an exception/error, please use
+     * {@link Observation#error(Throwable)} instead.
+     */
+    class Event {
+
+        private final String name;
+
+        private final String contextualName;
+
+        /**
+         * @param name The name of the event.
+         */
+        public Event(String name) {
+            this(name, name);
+        }
+
+        /**
+         * @param name The name of the event (should have low cardinality).
+         * @param contextualName The contextual name of the event (can have high
+         * cardinality).
+         */
+        public Event(String name, String contextualName) {
+            this.name = name;
+            this.contextualName = contextualName;
+        }
+
+        /**
+         * @return the name of the event.
+         */
+        public String getName() {
+            return this.name;
+        }
+
+        /**
+         * @return the contextual name of the event.
+         */
+        public String getContextualName() {
+            return this.contextualName;
+        }
+
+        @Override
+        public String toString() {
+            return "event.name='" + this.name + "', event.contextualName='" + this.contextualName + '\'';
+        }
+
+    }
+
     /**
      * Read only view on the {@link Context}.
      */
@@ -842,6 +900,7 @@ interface ContextView {
          * context (e.g. name derived from HTTP request).
          * @return contextual name
          */
+        @Nullable
         String getContextualName();
 
         /**

micrometer-observation/src/main/java/io/micrometer/observation/ObservationHandler.java

@@ -47,6 +47,14 @@ default void onStart(T context) {
     default void onError(T context) {
     }
 
+    /**
+     * Reacts to arbitrary {@link Observation.Event}.
+     * @param event the {@link Observation.Event} that was signaled
+     * @param context a {@link Observation.Context}
+     */
+    default void onEvent(Observation.Event event, T context) {
+    }
+
     /**
      * Reacts to opening of an {@link Observation.Scope}.
      * @param context an {@link Observation.Context}
@@ -131,6 +139,11 @@ public void onError(Observation.Context context) {
             getFirstApplicableHandler(context).ifPresent(handler -> handler.onError(context));
         }
 
+        @Override
+        public void onEvent(Observation.Event event, Observation.Context context) {
+            getFirstApplicableHandler(context).ifPresent(handler -> handler.onEvent(event, context));
+        }
+
         @Override
         public void onScopeOpened(Observation.Context context) {
             getFirstApplicableHandler(context).ifPresent(handler -> handler.onScopeOpened(context));
@@ -200,6 +213,11 @@ public void onError(Observation.Context context) {
             getAllApplicableHandlers(context).forEach(handler -> handler.onError(context));
         }
 
+        @Override
+        public void onEvent(Observation.Event event, Observation.Context context) {
+            getAllApplicableHandlers(context).forEach(handler -> handler.onEvent(event, context));
+        }
+
         @Override
         public void onScopeOpened(Observation.Context context) {
             getAllApplicableHandlers(context).forEach(handler -> handler.onScopeOpened(context));

micrometer-observation/src/main/java/io/micrometer/observation/ObservationTextPublisher.java

@@ -88,6 +88,11 @@ public void onError(Observation.Context context) {
         publish("ERROR", context);
     }
 
+    @Override
+    public void onEvent(Observation.Event event, Observation.Context context) {
+        publishUnformatted(String.format("%5s - %s, %s", "EVENT", event, converter.apply(context)));
+    }
+
     @Override
     public void onScopeOpened(Observation.Context context) {
         publish("OPEN", context);
@@ -109,7 +114,11 @@ public boolean supportsContext(Observation.Context context) {
     }
 
     private void publish(String event, Observation.Context context) {
-        this.consumer.accept(String.format("%5s - %s", event, converter.apply(context)));
+        publishUnformatted(String.format("%5s - %s", event, converter.apply(context)));
+    }
+
+    private void publishUnformatted(String event) {
+        this.consumer.accept(event);
     }
 
 }

micrometer-observation/src/main/java/io/micrometer/observation/SimpleObservation.java

@@ -129,6 +129,12 @@ public Observation error(Throwable error) {
         return this;
     }
 
+    @Override
+    public Observation event(Event event) {
+        this.notifyOnEvent(event);
+        return this;
+    }
+
     @Override
     public Observation start() {
         this.notifyOnObservationStarted();
@@ -177,6 +183,11 @@ private void notifyOnError() {
         this.handlers.forEach(handler -> handler.onError(this.context));
     }
 
+    @SuppressWarnings("unchecked")
+    private void notifyOnEvent(Event event) {
+        this.handlers.forEach(handler -> handler.onEvent(event, this.context));
+    }
+
     @SuppressWarnings("unchecked")
     private void notifyOnScopeOpened() {
         this.handlers.forEach(handler -> handler.onScopeOpened(this.context));