NPE during expiration check

[jorgheymans]

Just encountered this on a maven build (regular clean install, small single module project)

Apache Maven Daemon (mvnd) 1.0-m6 linux-amd64 native client (47d4c6b9c399079d91312bb8ae35d1d76e7fd97a)
Terminal: org.jline.terminal.impl.PosixSysTerminal with pty org.jline.terminal.impl.jansi.linux.LinuxNativePty
Apache Maven 3.9.1 (2e178502fcdbffc201671fb2537d0cb4b4cc58f8)
Maven home: /home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn
Java version: 11.0.18, vendor: IBM Corporation, runtime: /home/user/.sdkman/candidates/java/11.0.18-sem
Default locale: en, platform encoding: UTF-8
OS name: "linux", version: "5.19.0-41-generic", arch: "amd64", family: "unix"

11:42:54.378 D Expiration check running
11:42:54.378 E Problem in daemon expiration check
java.lang.NullPointerException: null
	at org.mvndaemon.mvnd.daemon.DaemonMemoryStatus.isTrashing(DaemonMemoryStatus.java:163)
	at org.mvndaemon.mvnd.daemon.DaemonExpiration.lambda$gcTrashing$0(DaemonExpiration.java:75)
	at org.mvndaemon.mvnd.daemon.DaemonExpiration.lambda$any$9(DaemonExpiration.java:200)
	at org.mvndaemon.mvnd.daemon.DaemonExpiration.lambda$any$9(DaemonExpiration.java:200)
	at org.mvndaemon.mvnd.daemon.Server.expirationCheck(Server.java:321)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:839)

daemon log:

Starting daemon process: id = ddb5dd8d, workingDir = /home/user/src/auditing, daemonArgs: /home/user/.sdkman/candidates/java/11.0.18-sem/bin/java -classpath /home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn/boot/plexus-classworlds-2.6.0.jar -javaagent:/home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn/lib/mvnd/mvnd-agent-1.0-m6.jar -client -XX:+ClassRelationshipVerifier -Dmvnd.home=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39 -Dmaven.home=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn -Dmaven.conf=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn/conf -Dclassworlds.conf=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39/bin/mvnd-daemon.conf -Dmvnd.java.home=/home/user/.sdkman/candidates/java/11.0.18-sem -Dlogback.configurationFile=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39/mvn/conf/logging/logback-daemon.xml -Dmvnd.id=ddb5dd8d -Dmvnd.daemonStorage=/home/user/.m2/mvnd/registry/1.0-m6 -Dmvnd.registry=/home/user/.m2/mvnd/registry/1.0-m6/registry.bin -Dmvnd.socketFamily=inet -Dmvnd.home=/home/user/.sdkman/candidates/mvnd/1.0-m6-m39 -Djdk.java.options=--add-opens java.base/java.io=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/sun.net.www.protocol.jar=ALL-UNNAMED --add-opens java.base/sun.nio.fs=ALL-UNNAMED -Dmvnd.noDaemon=false -Dmvnd.debug=false -Dmvnd.debug.address=8000 -Dmvnd.idleTimeout=3h -Dmvnd.keepAlive=100ms -Dmvnd.extClasspath= -Dmvnd.coreExtensions= -Dmvnd.jvmArgs=-client -XX:+ClassRelationshipVerifier -Dmvnd.enableAssertions=false -Dmvnd.expirationCheckDelay=10s -Dmvnd.duplicateDaemonGracePeriod=10s -Dmvnd.socketFamily=inet org.codehaus.plexus.classworlds.launcher.LauncherNOTE: Picked up JDK_JAVA_OPTIONS: --add-opens java.base/java.io=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/sun.net.www.protocol.jar=ALL-UNNAMED --add-opens java.base/sun.nio.fs=ALL-UNNAMED

It's not really reproducable, subsequent builds run fine.

[ppalaga]

First a null strategy is a legit outcome of the code around here

maven-mvnd/daemon/src/main/java/org/mvndaemon/mvnd/daemon/DaemonMemoryStatus.java

Lines 110 to 142 in a15abc2

	for (GcStrategy testStrategy : GcStrategy.values()) {
	garbageCollector = garbageCollectors.stream()
	.filter(gc -> gc.getName().equals(testStrategy.garbageCollector))
	.findFirst()
	.orElse(null);
	heapMemoryPoolMXBean = memoryPoolMXBeans.stream()
	.filter(mp -> mp.getName().equals(testStrategy.heapMemoryPool))
	.findFirst()
	.orElse(null);
	nonHeapMemoryPoolMXBean = memoryPoolMXBeans.stream()
	.filter(mp -> mp.getName().equals(testStrategy.nonHeapMemoryPool))
	.findFirst()
	.orElse(null);
	if (garbageCollector != null && heapMemoryPoolMXBean != null && nonHeapMemoryPoolMXBean != null) {
	strategy = testStrategy;
	break;
	}
	}
	if (strategy != null) {
	this.strategy = strategy;
	this.garbageCollectorMXBean = garbageCollector;
	this.heapMemoryPoolMXBean = heapMemoryPoolMXBean;
	this.nonHeapMemoryPoolMXBean = nonHeapMemoryPoolMXBean;
	this.clock = Clock.systemUTC();
	executor.scheduleAtFixedRate(this::gatherData, 1, 1, TimeUnit.SECONDS);
	} else {
	this.strategy = null;
	this.garbageCollectorMXBean = null;
	this.heapMemoryPoolMXBean = null;
	this.nonHeapMemoryPoolMXBean = null;
	this.clock = null;
	}
	}

So isTrashing, isHeapSpaceExhausted & friends should not assume strategy being non-null

maven-mvnd/daemon/src/main/java/org/mvndaemon/mvnd/daemon/DaemonMemoryStatus.java

Lines 162 to 171 in a15abc2

	public boolean isTrashing() {
	if (strategy.heapUsageThreshold != 0 && strategy.thrashingThreshold != 0) {
	GcStats stats = heapStats();
	return stats != null
	&& stats.usedPercent >= strategy.heapUsageThreshold
	&& stats.gcRate >= strategy.thrashingThreshold;
	} else {
	return false;
	}
	}

Would you mind sending a PR?

Second, I wonder what GcStrategy params would catch your JVM Java version: 11.0.18, vendor: IBM Corporation, runtime: /home/user/.sdkman/candidates/java/11.0.18-sem?

maven-mvnd/daemon/src/main/java/org/mvndaemon/mvnd/daemon/DaemonMemoryStatus.java

Lines 49 to 53 in a15abc2

	ORACLE_PARALLEL_CMS("PS Old Gen", "Metaspace", "PS MarkSweep", 1.2, 80, 80, 5.0),
	ORACLE_6_CMS("CMS Old Gen", "Metaspace", "ConcurrentMarkSweep", 1.2, 80, 80, 5.0),
	ORACLE_SERIAL("Tenured Gen", "Metaspace", "MarkSweepCompact", 1.2, 80, 80, 5.0),
	ORACLE_G1("G1 Old Gen", "Metaspace", "G1 Old Generation", 0.4, 75, 80, 2.0),
	IBM_ALL("Java heap", "Not Used", "MarkSweepCompact", 0.8, 70, -1, 6.0);