Spring Boot startup time: bean-by-bean diagnosis, and one directory per post

Adds spring-boot-startup-time/, the companion project for BLOG-618: a runnable Spring Boot 4.1.1 application on JDK 25 that installs BufferingApplicationStartup and FlightRecorderApplicationStartup behind a system property, and a /diag/startup endpoint that computes step self time -- the number /actuator/startup does not give you and the one that names the actual culprits. Captured under docs/output/: the step tree sorted both ways, the same startup as JFR events, a +5000-class experiment putting 0.11 ms per scanned class on the classpath scan tax, the silent truncation a 2048-step buffer performs, and JDK 25 AOT cache timings (6.93 s to 4.82 s). Post body and metadata live in post/. Moves the existing Actuator project into actuator-in-production/ so the repository holds one directory per article; the root README is now an index.
2026-09-04 23:58:38 +05:30
parent 4b6cefa60a
commit 958b401f0f
112 changed files with 2744 additions and 154 deletions
--- a/spring-boot-startup-time/docs/output/03-jfr.txt
+++ b/spring-boot-startup-time/docs/output/03-jfr.txt
@@ -0,0 +1,60 @@
+Started StartupDiagnosisApplication in 7.441 seconds (process running for 8.49)
+
+=== jfr summary (Spring rows only) ===
+
+ Version: 2.1
+ Chunks: 1
+=========================================================================================
+ org.springframework.core.metrics.jfr.FlightRecorderStartupEvent       398         33261
+
+=== the event type, in full ===
+@Name("org.springframework.core.metrics.jfr.FlightRecorderStartupEvent")
+@Category("Spring Application")
+@Label("Startup Step")
+@Description("Spring Application Startup")
+class FlightRecorderStartupEvent extends jdk.jfr.Event {
+  @Label("Start Time")
+  @Timestamp("TICKS")
+  long startTime;
+
+  @Label("Duration")
+  @Timespan("TICKS")
+  long duration;
+
+  @Label("Event Thread")
+  @Description("Thread in which event was committed in")
+  Thread eventThread;
+
+  @Label("Stack Trace")
+  @Description("Stack Trace starting from the method the event was committed in")
+  StackTrace stackTrace;
+
+  long eventId;
+
+
+=== the selector matters: the event is named by its FQCN, not 'StartupEvent' ===
+  --events StartupEvent                     -> 0 events
+  --events 'org.springframework.core.*'     -> 398 events
+
+=== 8 slowest startup steps, straight out of the recording ===
+398 StartupEvent records in the recording
+
+      duration  name / tags
+PT6.544849841S  spring.context.refresh 
+PT2.263845435S  spring.beans.instantiate beanName=&entityManagerFactory,beanType=interface org.springframework.context.weaving.LoadTimeWeaverAware,
+PT1.500763631S  spring.context.beans.post-process 
+PT1.202591188S  spring.context.beandef-registry.post-process postProcessor=org.springframework.context.annotation.ConfigurationClassPostProcessor@76b224cd,
+PT1.176668418S  spring.context.config-classes.parse classCount=130,
+PT0.538651275S  spring.beans.instantiate beanName=reportTemplateRegistry,
+ PT0.53548451S  spring.beans.instantiate beanName=tariffCacheWarmer,beanType=class com.ankurm.startup.slow.TariffCacheWarmer,
+PT0.515340537S  spring.boot.webserver.create factory=class org.springframework.boot.tomcat.servlet.TomcatServletWebServerFactory,
+
+=== what JFR gives you that the buffer does not: JVM context in the same file ===
+ jdk.ExecutionSample                                                   345          3787
+ jdk.GCPhasePauseLevel1                                                132          5281
+ jdk.GCPhasePauseLevel2                                                 50          1744
+ jdk.GCPhasePause                                                       39           937
+ jdk.Compilation                                                        16           452
+ jdk.ClassLoaderStatistics                                              10           260
+
+  total GC pause time during this startup: 39 events, 289.8 ms