Add application startup metrics support

This commit adds a new `StartupStep` interface and its factory
`ApplicationStartup`. Such steps are created, tagged with metadata and
thir execution time can be recorded - in order to collect metrics about
the application startup.

The default implementation is a "no-op" variant and has no side-effect.
Other implementations can record and collect events in a dedicated
metrics system or profiling tools. We provide here an implementation for
recording and storing steps with Java Flight Recorder.

This commit also instruments the Spring application context to gather
metrics about various phases of the application context, such as:

* context refresh phase
* bean definition registry post-processing
* bean factory post-processing
* beans instantiation and post-processing

Third part libraries involved in the Spring application context can
reuse the same infrastructure to record similar metrics.

Closes gh-24878

Author: bclozel

spring-beans/src/main/java/org/springframework/beans/factory/config/ConfigurableBeanFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -26,6 +26,7 @@
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.HierarchicalBeanFactory;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.metrics.ApplicationStartup;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.lang.Nullable;
 import org.springframework.util.StringValueResolver;
@@ -276,6 +277,20 @@ public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, Single
 	@Nullable
 	Scope getRegisteredScope(String scopeName);
 
+	/**
+	 * Set the {@code ApplicationStartup} for this bean factory.
+	 * <p>This allows the application context to record metrics during application startup.
+	 * @param applicationStartup the new application startup
+	 * @since 5.3.0
+	 */
+	void setApplicationStartup(ApplicationStartup applicationStartup);
+
+	/**
+	 * Return the {@code ApplicationStartup} for this bean factory.
+	 * @since 5.3.0
+	 */
+	ApplicationStartup getApplicationStartup();
+
 	/**
 	 * Provides a security access control context relevant to this factory.
 	 * @return the applicable AccessControlContext (never {@code null})

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -69,6 +69,8 @@
 import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
 import org.springframework.beans.factory.config.Scope;
 import org.springframework.beans.factory.config.SmartInstantiationAwareBeanPostProcessor;
+import org.springframework.beans.metrics.ApplicationStartup;
+import org.springframework.beans.metrics.StartupStep;
 import org.springframework.core.AttributeAccessor;
 import org.springframework.core.DecoratingClassLoader;
 import org.springframework.core.NamedThreadLocal;
@@ -178,6 +180,8 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	private final ThreadLocal<Object> prototypesCurrentlyInCreation =
 			new NamedThreadLocal<>("Prototype beans currently in creation");
 
+	/** Application startup metrics. **/
+	private ApplicationStartup applicationStartup = ApplicationStartup.getDefault();
 
 	/**
 	 * Create a new AbstractBeanFactory.
@@ -297,6 +301,11 @@ else if (requiredType != null) {
 			}
 
 			try {
+				StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate")
+						.tag("beanName", name);
+				if (requiredType != null) {
+					beanCreation.tag("beanType", requiredType::toString);
+				}
 				RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
 				checkMergedBeanDefinition(mbd, beanName, args);
 
@@ -374,6 +383,7 @@ else if (mbd.isPrototype()) {
 						throw new ScopeNotActiveException(beanName, scopeName, ex);
 					}
 				}
+				beanCreation.end();
 			}
 			catch (BeansException ex) {
 				cleanupAfterBeanCreationFailure(beanName);
@@ -1044,6 +1054,17 @@ public void setSecurityContextProvider(SecurityContextProvider securityProvider)
 		this.securityContextProvider = securityProvider;
 	}
 
+	@Override
+	public void setApplicationStartup(ApplicationStartup applicationStartup) {
+		Assert.notNull(applicationStartup, "applicationStartup should not be null");
+		this.applicationStartup = applicationStartup;
+	}
+
+	@Override
+	public ApplicationStartup getApplicationStartup() {
+		return this.applicationStartup;
+	}
+
 	/**
 	 * Delegate the creation of the access control context to the
 	 * {@link #setSecurityContextProvider SecurityContextProvider}.
@@ -1380,7 +1401,7 @@ protected RootBeanDefinition getMergedBeanDefinition(
 							else {
 								throw new NoSuchBeanDefinitionException(parentBeanName,
 										"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +
-										"': cannot be resolved without a ConfigurableBeanFactory parent");
+												"': cannot be resolved without a ConfigurableBeanFactory parent");
 							}
 						}
 					}
@@ -2068,7 +2089,7 @@ public void replaceAll(UnaryOperator<BeanPostProcessor> operator) {
 			super.replaceAll(operator);
 			beanPostProcessorCache = null;
 		}
-	};
+	}
 
 
 	/**

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -71,6 +71,7 @@
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.config.DependencyDescriptor;
 import org.springframework.beans.factory.config.NamedBeanHolder;
+import org.springframework.beans.metrics.StartupStep;
 import org.springframework.core.OrderComparator;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.MergedAnnotation;
@@ -564,7 +565,7 @@ private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSi
 								matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
 							}
 						}
-						else  {
+						else {
 							if (includeNonSingletons || isNonLazyDecorated ||
 									(allowFactoryBeanInit && isSingleton(beanName, mbd, dbd))) {
 								matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
@@ -937,6 +938,8 @@ public void preInstantiateSingletons() throws BeansException {
 		for (String beanName : beanNames) {
 			Object singletonInstance = getSingleton(beanName);
 			if (singletonInstance instanceof SmartInitializingSingleton) {
+				StartupStep smartInitialize = this.getApplicationStartup().start("spring.beans.smart-initialize")
+						.tag("beanName", beanName);
 				SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
 				if (System.getSecurityManager() != null) {
 					AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
@@ -947,6 +950,7 @@ public void preInstantiateSingletons() throws BeansException {
 				else {
 					smartSingleton.afterSingletonsInstantiated();
 				}
+				smartInitialize.end();
 			}
 		}
 	}
@@ -1672,7 +1676,7 @@ protected String determineHighestPriorityCandidate(Map<String, Object> candidate
 						if (candidatePriority.equals(highestPriority)) {
 							throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
 									"Multiple beans found with the same priority ('" + highestPriority +
-									"') among candidates: " + candidates.keySet());
+											"') among candidates: " + candidates.keySet());
 						}
 						else if (candidatePriority < highestPriority) {
 							highestPriorityBeanName = candidateBeanName;
@@ -1758,7 +1762,7 @@ private void raiseNoMatchingBeanFound(
 
 		throw new NoSuchBeanDefinitionException(resolvableType,
 				"expected at least 1 bean which qualifies as autowire candidate. " +
-				"Dependency annotations: " + ObjectUtils.nullSafeToString(descriptor.getAnnotations()));
+						"Dependency annotations: " + ObjectUtils.nullSafeToString(descriptor.getAnnotations()));
 	}
 
 	/**
@@ -1803,6 +1807,7 @@ private Optional<?> createOptionalDependency(
 			public boolean isRequired() {
 				return false;
 			}
+
 			@Override
 			public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory) {
 				return (!ObjectUtils.isEmpty(args) ? beanFactory.getBean(beanName, args) :
@@ -2019,6 +2024,7 @@ public Object getIfUnique() throws BeansException {
 				public boolean isRequired() {
 					return false;
 				}
+
 				@Override
 				@Nullable
 				public Object resolveNotUnique(ResolvableType type, Map<String, Object> matchingBeans) {

spring-beans/src/main/java/org/springframework/beans/metrics/ApplicationStartup.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2020 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.beans.metrics;
+
+/**
+ * Instruments the application startup phase using {@link StartupStep steps}.
+ * <p>The core container and its infrastructure components can use the {@code ApplicationStartup}
+ * to mark steps during the application startup and collect data about the execution context
+ * or their processing time.
+ *
+ * @author Brian Clozel
+ * @since 5.3.0
+ */
+public interface ApplicationStartup {
+
+	/**
+	 * Return a default "no op" {@code ApplicationStartup} implementation.
+	 * <p>This variant is designed for minimal overhead and does not record data.
+	 */
+	static ApplicationStartup getDefault() {
+		return new DefaultApplicationStartup();
+	}
+
+	/**
+	 * Create a new step and marks its beginning.
+	 * <p>A step name describes the current action or phase. This technical
+	 * name should be "." namespaced and can be reused to describe other instances of
+	 * the same step during application startup.
+	 * @param name the step name
+	 */
+	StartupStep start(String name);
+
+}

spring-beans/src/main/java/org/springframework/beans/metrics/DefaultApplicationStartup.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2002-2020 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.beans.metrics;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.function.Supplier;
+
+/**
+ * Default "no op" {@code ApplicationStartup} implementation.
+ * <p>This variant is designed for minimal overhead and does not record events.
+ *
+ * @author Brian Clozel
+ */
+class DefaultApplicationStartup implements ApplicationStartup {
+
+	@Override
+	public DefaultStartupStep start(String name) {
+		return new DefaultStartupStep();
+	}
+
+	static class DefaultStartupStep implements StartupStep {
+
+		boolean recorded = false;
+
+		private final DefaultTags TAGS = new DefaultTags();
+
+		@Override
+		public String getName() {
+			return "default";
+		}
+
+		@Override
+		public long getId() {
+			return 0L;
+		}
+
+		@Override
+		public Long getParentId() {
+			return null;
+		}
+
+		@Override
+		public Tags tags() {
+			return this.TAGS;
+		}
+
+		@Override
+		public StartupStep tag(String key, String value) {
+			if (this.recorded) {
+				throw new IllegalArgumentException();
+			}
+			return this;
+		}
+
+		@Override
+		public StartupStep tag(String key, Supplier<String> value) {
+			if (this.recorded) {
+				throw new IllegalArgumentException();
+			}
+			return this;
+		}
+
+		@Override
+		public void end() {
+			this.recorded = true;
+		}
+
+		static class DefaultTags implements StartupStep.Tags {
+
+			@Override
+			public Iterator<StartupStep.Tag> iterator() {
+				return Collections.emptyIterator();
+			}
+		}
+	}
+
+}