asmhatreandClaude Sonnet 5
e478eafda3
Companion code for Zero-Downtime Database Migrations: Expand-Contract in Practice with Spring Boot: a full expand/migrate-writes/migrate-reads/contract sequence run as an actual rolling deploy across two live replicas, with a load generator sending continuous HTTP traffic through all four deploys (99.98% success, every residual error traced to a root cause rather than left unexplained). Findings include a real NOT NULL constraint trap in the expand migration, a backfill-window bug in the read switch, H2's AUTO_SERVER=TRUE single-point-of-failure behavior under a rolling restart, the drain-before-SIGTERM fix needed to close a health-check gap during graceful shutdown, and H2 silently discarding a concurrently committed INSERT during an ALTER TABLE ADD/DROP COLUMN rebuild - confirmed, by primary source, to be an H2-specific behavior rather than a property of the technique itself. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_019Fb7vW8vLyLKngBc4R3huA
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spring-boot-demo
Companion code for the Spring Boot articles on ankurm.com.
One directory per article. Each is a self-contained Maven project with its own README.md,
numbered documentation chapters under docs/, and captured real output under docs/output/
that a single script regenerates. Every figure quoted in an article came out of one of those
files.
| Directory | Article | What it demonstrates |
|---|---|---|
actuator-in-production/ |
Spring Boot Actuator in Production | endpoint exposure defaults, securing Actuator, custom health indicators and how they hang |
spring-boot-startup-time/ |
Why Your Spring Boot App Takes 8 Seconds to Start | BufferingApplicationStartup, JFR startup events, self time vs total time, the classpath-scan tax, the JDK 25 AOT cache |
configuration-properties/ |
@ConfigurationProperties vs @Value in Spring Boot 4 | relaxed binding measured three ways, record constructor binding, validation, IDE metadata generation |
profiles-and-config/ |
Spring Boot Profiles Done Right | the precedence stack made visible, config trees and ConfigMaps, why a profile file loses to an environment variable |
spring-aop/ |
Spring AOP Explained | every pointcut designator with real matches, JDK vs CGLIB proxies, six aspects that do not fire |
docker-images/ |
Dockerizing Spring Boot 4: Layered Jars, Buildpacks, Distroless and Image Size Benchmarks | one service packaged nine ways and measured: size on disk and pushed, rebuild delta, startup, PID 1 and signals, jlink, the JDK 25 AOT cache |
kubernetes-deployment/ |
Deploying Spring Boot 4 on Kubernetes | probe groups under a dependency outage, graceful shutdown under load four ways, JVM ergonomics per pod shape, CPU limits throttling GC, HPA on a Micrometer metric |
problem-details/ |
Global Exception Handling with ProblemDetail (RFC 9457) in Spring Boot 4 | thirteen failures under five handling setups, validation errors, i18n, content negotiation, errors outside MVC, silent 500s, decoding on the client |
resilience/ |
Spring Framework 7's Built-in Resilience: @Retryable, @ConcurrencyLimit, and What's Left for Resilience4j | @Retryable and @ConcurrencyLimit counted invocation by invocation, retries inside transactions, where Resilience4j still earns its place, migrating from Spring Retry |
caching/ |
The Spring Cache Abstraction: @Cacheable, @CacheEvict, Key Generators and the Self-Invocation Trap | the self-invocation trap measured four ways, the key collision SimpleKeyGenerator makes easy, eviction timing under a thrown exception, a rollback the cache keeps, and where this sits next to Hibernate's L2 cache |
spring-batch/ |
Spring Batch on Boot 4.1: Jobs, Steps, Chunk Processing and Restartability | a job that fails mid-chunk and resumes exactly where it left off across two separate JVMs, skip vs. restart on the same poisoned row, the resourceless job repository that forgets a restart ever happened, and the chunk(int) vs chunk(int, tx) builder split |
spring-batch-partitioning/ |
Spring Batch Partitioning and Parallel Steps: Scaling a 10-Million-Row Job | the real grid-size sweep at 10M and 300K rows (best speedup 1.42x, on 2 cores), MultiResourcePartitioner ignoring gridSize entirely, a rejected partition's StepExecution stuck at STARTING forever, and Spring Batch 6.0's new JobOperator#recover unsticking it |
db-migrations-flyway-liquibase/ |
Flyway vs Liquibase for Spring Boot 4: Migrations, Rollbacks and Baselines | Flyway Community's undo throwing FlywayRedgateEditionRequiredException at runtime, a real Liquibase 5.0.3 filename-caching defect that produces a phantom successful run, Liquibase's 10-second default lock-poll rate versus Flyway's near-instant row lock, the FSL license change and its ASF/Keycloak fallout, and what actually happens when both tools are enabled against one database |
db-migrations-expand-contract/ |
Zero-Downtime Database Migrations: Expand-Contract in Practice with Spring Boot | a real 4-deploy rolling sequence against two live replicas with a load generator proving 99.98% success, H2's AUTO_SERVER single-point-of-failure trap, a NOT NULL constraint that fails every Stage 4 insert, and ALTER TABLE silently dropping a concurrently committed row with no exception thrown |
Articles whose text is kept here rather than only on the blog have it under
<directory>/post/ — post.md for the body and meta.md for the title, excerpt and
categories.
Running any of them
Each project needs a JDK 25 and Maven 3.9. docker-images also needs Docker, and
kubernetes-deployment Docker plus a Kubernetes cluster; their READMEs list the rest:
cd <directory>
export JAVA_HOME=/path/to/jdk-25
mvn -DskipTests package
./scripts/run-all.sh # regenerate every transcript under docs/output/
Licence
MIT — see LICENSE.