Spring Boot 4 Actuator in production: endpoints, security, custom health indicators

Companion repository for the ankurm.com article. Every transcript in docs/output/
was produced by running this project; scripts/run-all.sh regenerates all of them.

Verified against Spring Boot 4.1.1 / Framework 7.0.9 / Security 7.1.1 /
Micrometer 1.17.1 / kafka-clients 4.2.1 on Temurin JDK 25.0.4.1+1.

scripts/demo-kafka-timeout.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+# The single most useful number in this repository: how long a naive Kafka health check blocks.
+set -uo pipefail
+cd "$(dirname "$0")/.."
+OUT=docs/output/09-kafka-timeout.txt
+MODE="${1:-tuned}"
+B=http://localhost:8080/actuator/health/kafka
+{
+  echo "### Kafka health check against an unreachable broker -- ${MODE}"
+  echo
+  echo "\$ time curl -s $B"
+  s=$(date +%s.%N)
+  body=$(curl -s -u ops:ops-password --max-time 180 "$B")
+  e=$(date +%s.%N)
+  echo "$body" | python3 -m json.tool 2>/dev/null || echo "$body"
+  echo
+  printf 'wall clock: %.1f s\n' "$(echo "$e - $s" | bc)"
+} > "$OUT.$MODE" 2>&1
+echo "wrote $OUT.$MODE"