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/actuator-in-production/docs/output/07-custom-health-indicators.txt
+++ b/actuator-in-production/docs/output/07-custom-health-indicators.txt
@@ -0,0 +1,121 @@
+### profile: details    (show-details: always, show-components: always)
+
+--- upstream UP ---
+$ curl -s -o /dev/null -w '%{http_code}' http://localhost:8080/actuator/health
+  HTTP 503
+{
+    "components": {
+        "db": {
+            "details": {
+                "database": "H2",
+                "validationQuery": "isValid()"
+            },
+            "status": "UP"
+        },
+        "diskSpace": {
+            "details": {
+                "total": 10213466112,
+                "free": 3877675008,
+                "threshold": 10485760,
+                "path": "/tmp/work/spring-boot-demo/.",
+                "exists": true
+            },
+            "status": "UP"
+        },
+        "externalApi": {
+            "details": {
+                "url": "http://localhost:8080/stub/upstream/ping",
+                "response": "pong",
+                "latencyMs": 66,
+                "timeoutMs": 750
+            },
+            "status": "UP"
+        },
+        "kafka": {
+            "details": {
+                "bootstrap": "localhost:9092",
+                "tuned": true,
+                "error": "TimeoutException: null",
+                "probeMs": 1500,
+                "budgetMs": 1500
+            },
+            "status": "DOWN"
+        },
+        "livenessState": {
+            "status": "UP"
+        },
+        "ordersDatabase": {
+            "details": {
+                "orders": 3,
+                "queryMs": 0,
+                "slowThresholdMs": 250
+            },
+            "status": "UP"
+        },
+        "ping": {
+            "status": "UP"
+        },
+        "readinessState": {
+            "status": "UP"
+        },
+        "ssl": {
+            "details": {
+                "expiringChains": [],
+                "invalidChains": [],
+                "validChains": []
+            },
+            "status": "UP"
+        }
+    },
+    "groups": [
+        "liveness",
+        "readiness"
+    ],
+    "status": "DOWN"
+}
+
+--- flip the upstream to DOWN, change nothing else ---
+$ curl -s -X POST 'http://localhost:8080/stub/upstream/mode?value=down'
+upstream mode = DOWN
+  HTTP 503
+{
+  "status": "DOWN",
+  "externalApi": {
+    "details": {
+      "error": "org.springframework.web.client.HttpServerErrorException$ServiceUnavailable: 503 : \"upstream unavailable\"",
+      "url": "http://localhost:8080/stub/upstream/ping",
+      "latencyMs": 67,
+      "timeoutMs": 750
+    },
+    "status": "DOWN"
+  }
+}
+
+  The aggregate went DOWN and /actuator/health now answers 503. If that URL is your
+  Kubernetes readiness probe, every pod in the deployment has just left the load
+  balancer because a third party had a bad minute.
+
+--- a single component, addressed directly ---
+$ curl -s http://localhost:8080/actuator/health/ordersDatabase
+{
+    "details": {
+        "orders": 3,
+        "queryMs": 0,
+        "slowThresholdMs": 250
+    },
+    "status": "UP"
+}
+$ curl -s http://localhost:8080/actuator/health/kafka
+{
+    "details": {
+        "bootstrap": "localhost:9092",
+        "tuned": true,
+        "error": "TimeoutException: null",
+        "probeMs": 1500,
+        "budgetMs": 1500
+    },
+    "status": "DOWN"
+}
+
+--- restore ---
+upstream mode = UP