Another test #38
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Another test #38
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deejgregor
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Oct 14, 2025
In DumpDrain, the collectTraces method replaces the 'data' field with an empty ArrayList, but at the same time, it does not also reset the 'index' field. If another dump is performed later, this leads the get method reaching the 'return null' statement, and as the comment states, this can (and does) break the queue. This change does a few things: - Resets the index in collectTraces when the data field is replaced (and marks the index field as volatile). This should prevent the above situation from happening. - In case the situation still happens, a stand-in CommandElement is returned to avoid returning null. A warning message is also logged. - The existing "testing tracer flare dump with multiple traces" test case is expanded to exercise problem. Here is an example stack trace when the hang happens: "dd-trace-monitor" DataDog#38 daemon prio=5 os_prio=31 tid=0x0000000110e6e000 nid=0x7617 runnable [0x0000000171032000] java.lang.Thread.State: RUNNABLE at org.jctools.queues.MpscBlockingConsumerArrayQueue.spinWaitForElement(MpscBlockingConsumerArrayQueue.java:634) at org.jctools.queues.MpscBlockingConsumerArrayQueue.parkUntilNext(MpscBlockingConsumerArrayQueue.java:566) at org.jctools.queues.MpscBlockingConsumerArrayQueue.take(MpscBlockingConsumerArrayQueue.java:482) at datadog.trace.core.PendingTraceBuffer$DelayingPendingTraceBuffer$Worker.run(PendingTraceBuffer.java:317) at java.lang.Thread.run(Thread.java:750)
deejgregor
added a commit
to deejgregor/dd-trace-java
that referenced
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Oct 16, 2025
In DumpDrain, the collectTraces method replaces the 'data' field with an empty ArrayList, but at the same time, it does not also reset the 'index' field. If another dump is performed later, this leads the get method reaching the 'return null' statement, and as the comment states, this can (and does) break the queue. This change does a few things: - Resets the index in collectTraces when the data field is replaced (and marks the index field as volatile). This should prevent the above situation from happening. - In case the situation still happens, a stand-in CommandElement is returned to avoid returning null. A warning message is also logged. - The existing "testing tracer flare dump with multiple traces" test case is expanded to exercise problem. Here is an example stack trace when the hang happens: "dd-trace-monitor" DataDog#38 daemon prio=5 os_prio=31 tid=0x0000000110e6e000 nid=0x7617 runnable [0x0000000171032000] java.lang.Thread.State: RUNNABLE at org.jctools.queues.MpscBlockingConsumerArrayQueue.spinWaitForElement(MpscBlockingConsumerArrayQueue.java:634) at org.jctools.queues.MpscBlockingConsumerArrayQueue.parkUntilNext(MpscBlockingConsumerArrayQueue.java:566) at org.jctools.queues.MpscBlockingConsumerArrayQueue.take(MpscBlockingConsumerArrayQueue.java:482) at datadog.trace.core.PendingTraceBuffer$DelayingPendingTraceBuffer$Worker.run(PendingTraceBuffer.java:317) at java.lang.Thread.run(Thread.java:750)
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