Null pointer in tablet servers compaction metrics code.

[keith-turner]

Describe the bug

Observed the following stack trace in tablet server logs.

2025-02-24T23:05:56,261 [threads.ThreadPools] ERROR: Non-critical scheduled background task failed
java.util.concurrent.ExecutionException: java.lang.NullPointerException: Cannot invoke "java.util.concurrent.atomic.AtomicInteger.set(int)" because "cem.running" is null
        at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:?]
        at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191) ~[?:?]
        at org.apache.accumulo.core.util.threads.ThreadPools.checkTaskFailed(ThreadPools.java:151) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at org.apache.accumulo.core.util.threads.ThreadPools$1.lambda$run$0(ThreadPools.java:120) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[?:?]
        at org.apache.accumulo.core.util.threads.ThreadPools$1.run(ThreadPools.java:117) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at org.apache.accumulo.core.trace.TraceWrappedRunnable.run(TraceWrappedRunnable.java:52) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) ~[?:?]
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[?:?]
        at org.apache.accumulo.core.trace.TraceWrappedRunnable.run(TraceWrappedRunnable.java:52) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at java.base/java.lang.Thread.run(Thread.java:840) [?:?]
Caused by: java.lang.NullPointerException: Cannot invoke "java.util.concurrent.atomic.AtomicInteger.set(int)" because "cem.running" is null
        at org.apache.accumulo.tserver.metrics.CompactionExecutorsMetrics.lambda$update$4(CompactionExecutorsMetrics.java:148) ~[accumulo-tserver-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[?:?]
        at org.apache.accumulo.tserver.metrics.CompactionExecutorsMetrics.update(CompactionExecutorsMetrics.java:147) ~[accumulo-tserver-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at org.apache.accumulo.core.trace.TraceWrappedRunnable.run(TraceWrappedRunnable.java:52) ~[accumulo-core-2.1.4-SNAPSHOT.jar:2.1.4-SNAPSHOT]
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539) ~[?:?]
        at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) ~[?:?]
        at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) ~[?:?]
        ... 4 more

[kevinrr888]

I'll look into this