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 29676e0cc8
110 changed files with 2577 additions and 154 deletions
@@ -0,0 +1,44 @@
+# Post metadata
+
+**Title**
+
+Why Your Spring Boot App Takes 8 Seconds to Start: A Bean-by-Bean Diagnosis
+
+**Slug**
+
+`spring-boot-startup-time-bean-by-bean-diagnosis`
+
+**Excerpt**
+
+Spring Boot logs one startup number and hides four phases behind it. This walks through
+turning on the `ApplicationStartup` instrumentation that ships switched off, reading the
+step tree by self time rather than total duration — the mistake that makes people optimise
+a bean costing 10 ms instead of the one costing 504 — and then puts measured numbers on
+component scanning (0.11 ms per class inspected, whether or not it is a bean), on the
+silent truncation a 2048-step buffer performs on your recording, and on the JDK 25 AOT
+cache, which took 6.93 s to 4.82 s on the companion project without a line of application
+code changing.
+
+**Categories**
+
+Java (328), Spring (355)
+
+**Yoast**
+
+- `_yoast_wpseo_title`: Spring Boot Startup Time: A Bean-by-Bean Diagnosis
+- `_yoast_wpseo_metadesc`: Turn on Spring Boot's built-in startup instrumentation, read the step tree by self time, and see measured numbers for component scanning, buffer truncation and the JDK 25 AOT cache.
+- `_yoast_wpseo_focuskw`: spring boot startup time
+
+**Companion repository**
+
+`asmhatre/spring-boot-demo` → [`spring-boot-startup-time/`](../)
+
+**Jira**
+
+BLOG-618
+
+**Verified against**
+
+Spring Boot 4.1.1 (GA 20 August 2026), Spring Framework 7.0.9, Spring Data JPA 4.1.1,
+Hibernate ORM 7.4.5.Final, Tomcat 11.0.24, Micrometer 1.17.1, H2 2.4.240,
+Temurin 25.0.4.1+1 LTS, Maven 3.9.11.