Add jfr-demo: JFR + Mission Control profiling of a live Spring Boot app

Custom OrderProcessed event, CPU/allocation/lock workloads, a diagnostic endpoint over the JVM's live FlightRecorder state, a JUnit test using the jdk.jfr.Recording API, and nine captured recordings (flagship, mid-flight snapshot, isolated vs concurrent threshold comparisons, and a real dump+stop duplication bug) with their docs/output/*.txt transcripts.
2026-10-01 04:37:26 +00:00
commit c7eccd1db5
40 changed files with 1326 additions and 0 deletions
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+Top stack frames from jdk.ExecutionSample, live-demo.jfr, during six concurrent
+GET /api/cpu/fibonacci?n=38 calls, aggregated by the top (leaf) frame only.
+
+$ jfr print --events jdk.ExecutionSample --stack-depth 1 recordings/live-demo.jfr \
+    | grep -A1 stackTrace | grep -v 'stackTrace\|^--' | sed 's/^\s*//' | sort | uniq -c | sort -rn
+
+     62 com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+     13 com.ankurm.jfr.service.WorkloadService.churnAllocations(int) line: 56
+      9 com.ankurm.jfr.service.WorkloadService.churnAllocations(int) line: 52
+      2 jdk.internal.util.DecimalDigits.uncheckedGetCharsLatin1(int, int, byte[]) line: 168
+      1 org.apache.tomcat.util.net.NioEndpoint$Poller.run() line: 941
+      1 org.apache.tomcat.util.http.MimeHeaders.addValue(byte[], int, int) line: 327
+      1 org.apache.catalina.mapper.Mapper.compareIgnoreCase(CharChunk, int, int, String) line: 1401
+      1 org.apache.catalina.core.ApplicationFilterFactory.createFilterChain(ServletRequest, Wrapper, Servlet) line: 75
+      1 jdk.internal.util.DecimalDigits.stringSize(int) line: 101
+      1 jdk.internal.misc.Unsafe.allocateUninitializedArray(Class, int) line: 1396
+      1 java.util.concurrent.locks.LockSupport.unpark(Thread) line: 181
+      1 java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.signalAll() line: 1590
+      1 java.util.Arrays.copyOf(Object[], int) line: 3478
+      1 java.nio.Buffer.position(int) line: 325
+      1 java.lang.invoke.DirectMethodHandle.allocateInstance(Object) line: 500
+
+total jdk.ExecutionSample events in recording: 98
+fibonacci() share of samples: 62 / 98 = 63.3%
+
+$ jfr print --events jdk.ExecutionSample recordings/live-demo.jfr | head -13
+jdk.ExecutionSample {
+  startTime = 09:59:03.699 (2026-10-01)
+  sampledThread = "http-nio-8080-exec-1" (javaThreadId = 30)
+  state = "STATE_RUNNABLE"
+  stackTrace = [
+    com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+    com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+    com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+    com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+    com.ankurm.jfr.service.WorkloadService.fibonacci(int) line: 40
+    ...
+  ]
+}