Add support for reactor-tools debug agent

The `reactor-tools` dependency now brings a new Reactor Debug Agent
which instruments loaded classes for better Reactor stacktraces.
This commit removes the `spring.reactor.stacktrace-mode.enabled`
configuration property since the related Reactor Hook is about to be
removed.
As a replacement, we're introducing `spring.reactor.debug-agent.enabled`
which tells whether the Reactor Debug Agent should be loaded, given that
the `reactor-tools` dependency is available. This option is enabled by
default, since adding the dependency on classpath is a strong signal
already.

Fixes gh-17128

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -775,6 +775,14 @@
       "name": "spring.rabbitmq.listener.type",
       "defaultValue": "simple"
     },
+    {
+      "name": "spring.reactor.stacktrace-mode.enabled",
+      "description": "Whether Reactor should collect stacktrace information at runtime.",
+      "defaultValue": false,
+      "deprecation": {
+        "replacement": "spring.reactor.debug-agent.enabled"
+      }
+    },
     {
       "name": "spring.security.filter.dispatcher-types",
       "defaultValue": [

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -100,7 +100,6 @@ org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
 org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
 org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
 org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
-org.springframework.boot.autoconfigure.reactor.core.ReactorCoreAutoConfiguration,\
 org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,\
 org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,\
 org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,\

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/reactor/core/ReactorCoreAutoConfigurationTests.java

-/*
- * Copyright 2012-2019 the original author or authors.
- *
- * 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 org.springframework.boot.autoconfigure.reactor.core;
-
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import reactor.core.publisher.Hooks;
-
-import org.springframework.boot.autoconfigure.AutoConfigurations;
-import org.springframework.boot.test.context.assertj.AssertableApplicationContext;
-import org.springframework.boot.test.context.runner.ApplicationContextRunner;
-import org.springframework.boot.test.context.runner.ContextConsumer;
-import org.springframework.test.util.ReflectionTestUtils;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * Tests for {@link ReactorCoreAutoConfiguration}.
- *
- * @author Stephane Nicoll
- */
-class ReactorCoreAutoConfigurationTests {
-
-	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
-			.withConfiguration(AutoConfigurations.of(ReactorCoreAutoConfiguration.class));
-
-	@BeforeEach
-	@AfterEach
-	void resetDebugFlag() {
-		Hooks.resetOnOperatorDebug();
-	}
-
-	@Test
-	void debugOperatorIsDisabledByDefault() {
-		this.contextRunner.run(assertDebugOperator(false));
-	}
-
-	@Test
-	void debugOperatorIsSetWithProperty() {
-		this.contextRunner.withPropertyValues("spring.reactor.debug=true").run(assertDebugOperator(true));
-	}
-
-	@Test
-	@Deprecated
-	void debugOperatorIsSetWithDeprecatedProperty() {
-		this.contextRunner.withPropertyValues("spring.reactor.stacktrace-mode.enabled=true")
-				.run(assertDebugOperator(true));
-	}
-
-	private ContextConsumer<AssertableApplicationContext> assertDebugOperator(boolean expected) {
-		return (context) -> assertThat(ReflectionTestUtils.getField(Hooks.class, "GLOBAL_TRACE")).isEqualTo(expected);
-	}
-
-}

spring-boot-project/spring-boot/pom.xml

@@ -76,6 +76,11 @@
 			<artifactId>reactor-netty</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>io.projectreactor</groupId>
+			<artifactId>reactor-tools</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>io.netty</groupId>
 			<artifactId>netty-tcnative-boringssl-static</artifactId>

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/reactor/core/ReactorCoreProperties.java → spring-boot-project/spring-boot/src/main/java/org/springframework/boot/reactor/DebugAgentEnvironmentPostProcessor.java

@@ -14,52 +14,46 @@
  * limitations under the License.
  */
 
-package org.springframework.boot.autoconfigure.reactor.core;
+package org.springframework.boot.reactor;
 
-import org.springframework.boot.context.properties.ConfigurationProperties;
-import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
+import reactor.tools.agent.ReactorDebugAgent;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.env.EnvironmentPostProcessor;
+import org.springframework.core.Ordered;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.util.ClassUtils;
 
 /**
- * Properties for Reactor Core.
+ * {@link EnvironmentPostProcessor} to enable the Reactor Debug Agent if available.
+ * <p>
+ * The debug agent is enabled by default, unless the
+ * {@code "spring.reactor.debug-agent.enabled"} configuration property is set to false. We
+ * are using here an {@link EnvironmentPostProcessor} instead of an auto-configuration
+ * class to enable the agent as soon as possible during the startup process.
  *
  * @author Brian Clozel
- * @since 2.0.0
+ * @since 2.2.0
  */
-@ConfigurationProperties(prefix = "spring.reactor")
-public class ReactorCoreProperties {
-
-	/**
-	 * Whether Reactor should collect stacktrace information at runtime.
-	 */
-	private boolean debug;
-
-	private final StacktraceMode stacktraceMode = new StacktraceMode();
+public class DebugAgentEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered {
 
-	public boolean isDebug() {
-		return this.debug;
-	}
+	private static final String REACTOR_DEBUGAGENT_CLASS = "reactor.tools.agent.ReactorDebugAgent";
 
-	public void setDebug(boolean debug) {
-		this.debug = debug;
-	}
+	private static final String DEBUGAGENT_ENABLED_CONFIG_KEY = "spring.reactor.debug-agent.enabled";
 
-	public StacktraceMode getStacktraceMode() {
-		return this.stacktraceMode;
-	}
-
-	public class StacktraceMode {
-
-		@DeprecatedConfigurationProperty(replacement = "spring.reactor.debug")
-		@Deprecated
-		public boolean isEnabled() {
-			return isDebug();
-		}
-
-		@Deprecated
-		public void setEnabled(boolean enabled) {
-			setDebug(enabled);
+	@Override
+	public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
+		if (ClassUtils.isPresent(REACTOR_DEBUGAGENT_CLASS, null)) {
+			Boolean agentEnabled = environment.getProperty(DEBUGAGENT_ENABLED_CONFIG_KEY, Boolean.class);
+			if (agentEnabled != Boolean.FALSE) {
+				ReactorDebugAgent.init();
+			}
 		}
+	}
 
+	@Override
+	public int getOrder() {
+		return Ordered.LOWEST_PRECEDENCE;
 	}
 
 }

spring-boot-project/spring-boot/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -719,6 +719,13 @@
       "sourceType": "org.springframework.boot.context.config.ConfigFileApplicationListener",
       "description": "Unconditionally activate the specified comma-separated list of profiles (or list of profiles if using YAML)."
     },
+    {
+      "name": "spring.reactor.debug-agent.enabled",
+      "type": "java.lang.Boolean",
+      "sourceType": "org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor",
+      "description": "Whether the Reactor Debug Agent should be enabled when reactor-tools is present.",
+      "defaultValue": true
+    },
     {
       "name": "trace",
       "type": "java.lang.Boolean",

spring-boot-project/spring-boot/src/main/resources/META-INF/spring.factories

@@ -34,7 +34,8 @@ org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener
 org.springframework.boot.env.EnvironmentPostProcessor=\
 org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
 org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor,\
-org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor
+org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor,\
+org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor
 
 # Failure Analyzers
 org.springframework.boot.diagnostics.FailureAnalyzer=\

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/reactor/core/ReactorCoreAutoConfiguration.java → spring-boot-project/spring-boot/src/test/java/org/springframework/boot/reactor/DebugAgentEnvironmentPostProcessorTests.java

@@ -14,35 +14,35 @@
  * limitations under the License.
  */
 
-package org.springframework.boot.autoconfigure.reactor.core;
+package org.springframework.boot.reactor;
 
+import org.junit.jupiter.api.Test;
+import reactor.core.Scannable;
 import reactor.core.publisher.Flux;
-import reactor.core.publisher.Hooks;
-import reactor.core.publisher.Mono;
 
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.context.properties.EnableConfigurationProperties;
-import org.springframework.context.annotation.Configuration;
+import org.springframework.mock.env.MockEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * {@link EnableAutoConfiguration Auto-configuration} for Reactor Core.
+ * Tests for {@link DebugAgentEnvironmentPostProcessor}.
  *
  * @author Brian Clozel
- * @author Eddú Meléndez
- * @since 2.0.0
  */
-@Configuration(proxyBeanMethods = false)
-@ConditionalOnClass({ Mono.class, Flux.class })
-@EnableConfigurationProperties(ReactorCoreProperties.class)
-public class ReactorCoreAutoConfiguration {
-
-	@Autowired
-	protected void initialize(ReactorCoreProperties properties) {
-		if (properties.isDebug()) {
-			Hooks.onOperatorDebug();
-		}
+class DebugAgentEnvironmentPostProcessorTests {
+
+	static {
+		MockEnvironment environment = new MockEnvironment();
+		DebugAgentEnvironmentPostProcessor postProcessor = new DebugAgentEnvironmentPostProcessor();
+		postProcessor.postProcessEnvironment(environment, null);
+	}
+
+	@Test
+	void enablesReactorDebugAgent() {
+		InstrumentedFluxProvider fluxProvider = new InstrumentedFluxProvider();
+		Flux<Integer> flux = fluxProvider.newFluxJust();
+		assertThat(Scannable.from(flux).stepName())
+				.startsWith("Flux.just ⇢ at org.springframework.boot.reactor.InstrumentedFluxProvider.newFluxJust");
 	}
 
 }

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/reactor/core/package-info.java → spring-boot-project/spring-boot/src/test/java/org/springframework/boot/reactor/InstrumentedFluxProvider.java

 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,7 +14,20 @@
  * limitations under the License.
  */
 
+package org.springframework.boot.reactor;
+
+import reactor.core.publisher.Flux;
+
 /**
- * Auto-configuration for Reactor Core.
+ * Utility class that should be instrumented by the reactor debug agent.
+ *
+ * @author Brian Clozel
+ * @see DebugAgentEnvironmentPostProcessorTests
  */
-package org.springframework.boot.autoconfigure.reactor.core;
+class InstrumentedFluxProvider {
+
+	Flux<Integer> newFluxJust() {
+		return Flux.just(1);
+	}
+
+}