Add ObservationValidator

Closes gh-5239

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

@@ -0,0 +1,159 @@
+/*
+ * Copyright 2024 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.observation.tck;
+
+import io.micrometer.common.lang.Nullable;
+import io.micrometer.common.util.internal.logging.InternalLogger;
+import io.micrometer.common.util.internal.logging.InternalLoggerFactory;
+import io.micrometer.observation.Observation.Context;
+import io.micrometer.observation.Observation.Event;
+import io.micrometer.observation.ObservationHandler;
+
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+/**
+ * An {@link ObservationHandler} that validates the order of events of an Observation (for
+ * example stop should be called after start) and with a validation message and the
+ * original context, it publishes the events of these invalid scenarios to the
+ * {@link Consumer} of your choice.
+ *
+ * @author Jonatan Ivanov
+ */
+class ObservationValidator implements ObservationHandler<Context> {
+
+    private static final InternalLogger LOGGER = InternalLoggerFactory.getInstance(ObservationValidator.class);
+
+    private final Consumer<ValidationResult> consumer;
+
+    private final Predicate<Context> supportsContextPredicate;
+
+    ObservationValidator() {
+        this(validationResult -> LOGGER.warn(validationResult.toString()));
+    }
+
+    ObservationValidator(Consumer<ValidationResult> consumer) {
+        this(consumer, context -> true);
+    }
+
+    ObservationValidator(Consumer<ValidationResult> consumer, Predicate<Context> supportsContextPredicate) {
+        this.consumer = consumer;
+        this.supportsContextPredicate = supportsContextPredicate;
+    }
+
+    @Override
+    public void onStart(Context context) {
+        Status status = context.get(Status.class);
+        if (status != null) {
+            consumer.accept(new ValidationResult("Invalid start: Observation has already been started", context));
+        }
+        else {
+            context.put(Status.class, new Status());
+        }
+    }
+
+    @Override
+    public void onError(Context context) {
+        checkIfObservationWasStartedButNotStopped("Invalid error signal", context);
+    }
+
+    @Override
+    public void onEvent(Event event, Context context) {
+        checkIfObservationWasStartedButNotStopped("Invalid event signal", context);
+    }
+
+    @Override
+    public void onScopeOpened(Context context) {
+        checkIfObservationWasStartedButNotStopped("Invalid scope opening", context);
+    }
+
+    @Override
+    public void onScopeClosed(Context context) {
+        checkIfObservationWasStartedButNotStopped("Invalid scope closing", context);
+    }
+
+    @Override
+    public void onScopeReset(Context context) {
+        checkIfObservationWasStartedButNotStopped("Invalid scope resetting", context);
+    }
+
+    @Override
+    public void onStop(Context context) {
+        Status status = checkIfObservationWasStartedButNotStopped("Invalid stop", context);
+        if (status != null) {
+            status.markStopped();
+        }
+    }
+
+    @Override
+    public boolean supportsContext(Context context) {
+        return supportsContextPredicate.test(context);
+    }
+
+    @Nullable
+    private Status checkIfObservationWasStartedButNotStopped(String prefix, Context context) {
+        Status status = context.get(Status.class);
+        if (status == null) {
+            consumer.accept(new ValidationResult(prefix + ": Observation has not been started yet", context));
+        }
+        else if (status.isStopped()) {
+            consumer.accept(new ValidationResult(prefix + ": Observation has already been stopped", context));
+        }
+
+        return status;
+    }
+
+    static class ValidationResult {
+
+        private final String message;
+
+        private final Context context;
+
+        ValidationResult(String message, Context context) {
+            this.message = message;
+            this.context = context;
+        }
+
+        String getMessage() {
+            return message;
+        }
+
+        Context getContext() {
+            return context;
+        }
+
+        @Override
+        public String toString() {
+            return getMessage() + " - " + getContext();
+        }
+
+    }
+
+    static class Status {
+
+        private boolean stopped = false;
+
+        boolean isStopped() {
+            return stopped;
+        }
+
+        void markStopped() {
+            stopped = true;
+        }
+
+    }
+
+}

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

@@ -38,7 +38,7 @@ public final class TestObservationRegistry implements ObservationRegistry {
     private final StoringObservationHandler handler = new StoringObservationHandler();
 
     private TestObservationRegistry() {
-        observationConfig().observationHandler(this.handler);
+        observationConfig().observationHandler(this.handler).observationHandler(new ObservationValidator());
     }
 
     /**

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

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2024 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.observation.tck;
+
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.Observation.Event;
+import io.micrometer.observation.Observation.Scope;
+import io.micrometer.observation.ObservationRegistry;
+import io.micrometer.observation.tck.ObservationValidator.ValidationResult;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.function.Consumer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ObservationValidator}.
+ *
+ * @author Jonatan Ivanov
+ */
+class ObservationValidatorTests {
+
+    private TestConsumer testConsumer;
+
+    private ObservationRegistry registry;
+
+    @BeforeEach
+    void setUp() {
+        testConsumer = new TestConsumer();
+        registry = ObservationRegistry.create();
+        registry.observationConfig().observationHandler(new ObservationValidator(testConsumer));
+    }
+
+    @Test
+    void doubleStartShouldBeInvalid() {
+        Observation.start("test", registry).start();
+        assertThat(testConsumer.toString()).isEqualTo("Invalid start: Observation has already been started");
+    }
+
+    @Test
+    void stopBeforeStartShouldBeInvalid() {
+        Observation.createNotStarted("test", registry).stop();
+        assertThat(testConsumer.toString()).isEqualTo("Invalid stop: Observation has not been started yet");
+    }
+
+    @Test
+    void errorBeforeStartShouldBeInvalid() {
+        Observation.createNotStarted("test", registry).error(new RuntimeException());
+        assertThat(testConsumer.toString()).isEqualTo("Invalid error signal: Observation has not been started yet");
+    }
+
+    @Test
+    void eventBeforeStartShouldBeInvalid() {
+        Observation.createNotStarted("test", registry).event(Event.of("test"));
+        assertThat(testConsumer.toString()).isEqualTo("Invalid event signal: Observation has not been started yet");
+    }
+
+    @Test
+    void scopeBeforeStartShouldBeInvalid() {
+        Scope scope = Observation.createNotStarted("test", registry).openScope();
+        scope.reset();
+        scope.close();
+        assertThat(testConsumer.toString()).isEqualTo("Invalid scope opening: Observation has not been started yet\n"
+                + "Invalid scope resetting: Observation has not been started yet\n"
+                + "Invalid scope closing: Observation has not been started yet");
+    }
+
+    @Test
+    void observeAfterStartShouldBeInvalid() {
+        Observation.start("test", registry).observe(() -> "");
+        assertThat(testConsumer.toString()).isEqualTo("Invalid start: Observation has already been started");
+    }
+
+    @Test
+    void doubleStopShouldBeInvalid() {
+        Observation observation = Observation.start("test", registry);
+        observation.stop();
+        observation.stop();
+        assertThat(testConsumer.toString()).isEqualTo("Invalid stop: Observation has already been stopped");
+    }
+
+    @Test
+    void errorAfterStopShouldBeInvalid() {
+        Observation observation = Observation.start("test", registry);
+        observation.stop();
+        observation.error(new RuntimeException());
+        assertThat(testConsumer.toString()).isEqualTo("Invalid error signal: Observation has already been stopped");
+    }
+
+    @Test
+    void eventAfterStopShouldBeInvalid() {
+        Observation observation = Observation.start("test", registry);
+        observation.stop();
+        observation.event(Event.of("test"));
+        assertThat(testConsumer.toString()).isEqualTo("Invalid event signal: Observation has already been stopped");
+    }
+
+    @Test
+    void scopeAfterStopShouldBeInvalid() {
+        Observation observation = Observation.start("test", registry);
+        observation.stop();
+        Scope scope = observation.openScope();
+        scope.reset();
+        scope.close();
+        assertThat(testConsumer.toString()).isEqualTo("Invalid scope opening: Observation has already been stopped\n"
+                + "Invalid scope resetting: Observation has already been stopped\n"
+                + "Invalid scope closing: Observation has already been stopped");
+    }
+
+    static class TestConsumer implements Consumer<ValidationResult> {
+
+        private final StringBuilder stringBuilder = new StringBuilder();
+
+        @Override
+        public void accept(ValidationResult validationResult) {
+            stringBuilder.append(validationResult.getMessage()).append("\n");
+        }
+
+        @Override
+        public String toString() {
+            return stringBuilder.toString().trim();
+        }
+
+    }
+
+}