java.lang.Error:超过了SingleThreadExecutor的最大允许数

Question

在高流量下抛出以下异常，我不确定原因:

PcapHelper failed reading packet: packet: java.lang.Error: Maximum permit count exceeded(Maximum permit count exceeded) -> ST:
java.util.concurrent.Semaphore$Sync.tryReleaseShared(Semaphore.java:192) -> java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(AbstractQueuedSynchronizer.java:1341) ->
java.util.concurrent.Semaphore.release(Semaphore.java:609) -> org.jnetpcap.nio.DisposableGC.dispose(Unknown Source) -> org.jnetpcap.nio.DisposableGC.drainRefQueueBounded(Unknown Source)
-> org.jnetpcap.nio.DisposableReference.<init>(Unknown Source) -> org.jnetpcap.nio.JMemoryReference.<init>(Unknown Source) -> org.jnetpcap.nio.JMemory.createReference(Unknown Source) -
> org.jnetpcap.nio.JMemory.allocate(Unknown Source) -> org.jnetpcap.nio.JMemory.<init>(Unknown Source) -> org.jnetpcap.nio.JMemoryPool$Block.<init>(Unknown Source) -> org.jnetpcap.nio.J
MemoryPool.newBlock(Unknown Source) -> org.jnetpcap.nio.JMemoryPool.getBlock(Unknown Source) -> org.jnetpcap.nio.JMemoryPool.duplicate2(Unknown Source) -> org.jnetpcap.packet.PcapPacket
.transferHeaderAndDataFrom0(Unknown Source) -> org.jnetpcap.packet.PcapPacket.<init>(Unknown Source) -> com.topspin.intguard.utils.PcapHelper.lambda$getPacket$0(PcapHelper.java:199) -> java.util.concurrent.FutureTask.run(FutureTask.java:266) -> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) -> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) -> java.lang.Thread.run(Thread.java:748) ->

抛出异常的代码:

public static IPcapPacket getPacket(Pcap pcap, PcapHeader hdr, JBuffer buf, boolean isFirstPacket,
String interfaceName) throws InterruptedException, ExecutionException {
Future<IPcapPacket> result = null;
if (!SniffingService.isInProcess || isFirstPacket) {
result = sniffingExecutorService.submit(() -> {
PcapPacket pcapPacket = null;
try {
Log.Parsing.trace("{} getting packet for interface: {}", PcapHelper.class.getSimpleName(),
interfaceName);
if (pcap != null && pcap.nextEx(hdr, buf) == Pcap.NEXT_EX_OK) {
pcapPacket = new PcapPacket(hdr, buf);
}
if (isFirstPacket) {
Thread.sleep(500);
}
return getIPcapPacket(pcapPacket, interfaceName);
} catch (Throwable e) {
Log.Parsing.error("{} failed reading packet: packet: {}", PcapHelper.class.getSimpleName(),
ExceptionUtils.stackTraceToString(e));
if (pcapPacket != null) {
Log.Parsing.error("{} packet: {}", PcapHelper.class.getSimpleName(), pcapPacket.toString());
}
return null;
}
});
}
return result != null ? result.get() : null;
}

我猜这和未来号没有按时穿衣服有关，但我真的说不出是什么问题。

Answer 1

我做了以下更改，问题解决了:

public static IPcapPacket getPacket(Pcap pcap, PcapHeader hdr, JBuffer buf, boolean isFirstPacket,
String interfaceName) throws InterruptedException, ExecutionException {
Future<IPcapPacket> future = null;
if (!SniffingService.isInProcess || isFirstPacket) {
future = sniffingExecutorService.submit(() -> {
PcapPacket pcapPacket = null;
try {
Log.Parsing.trace("{} getting packet for interface: {}", PcapHelper.class.getSimpleName(),
interfaceName);
if (pcap != null && pcap.nextEx(hdr, buf) == Pcap.NEXT_EX_OK) {
pcapPacket = new PcapPacket(hdr, buf);
}
if (isFirstPacket) {
Thread.sleep(500);
}
return getIPcapPacket(pcapPacket, interfaceName);
} catch (Throwable e) {
Log.Parsing.error("{} failed reading packet: packet: {}", PcapHelper.class.getSimpleName(),
ExceptionUtils.stackTraceToString(e));
if (pcapPacket != null) {
Log.Parsing.error("{} packet: {}", PcapHelper.class.getSimpleName(), pcapPacket.toString());
}
return null;
}
});
}
IPcapPacket result = (future != null ? future.get() : null);
future = null;
return result;
}

将future更改为null可以解决这个问题。垃圾收集器知道这个future已经完成，并将其收集起来。