在使用slf4j的MDC做日志跟踪的时候，会因为MDC不能跨线程导致跟踪失败，此外，为了监控线上服务器的运行状态，也很有必要对线程池的运行情况进行监控。
下面是一个带有线程池监控且兼容MDC的线程池，建议使用！
/**
* A SLF4J MDC-compatible {@link ThreadPoolExecutor}.
* <p/>
* In general, MDC is used to store diagnostic information (e.g. a user's session id) in per-thread variables, to facilitate
* logging. However, although MDC data is passed to thread children, this doesn't work when threads are reused in a
* thread pool. This is a drop-in replacement for {@link ThreadPoolExecutor} sets MDC data before each task appropriately.
* <p/>
* Created by jlevy.
* Date: 6/14/13
*
* @author jlevy
*/
@Slf4j
public class MdcThreadPoolExecutor extends ThreadPoolExecutor {
@Getter
final private String name;
final private boolean useFixedContext;
final private Map<String, String> fixedContext;
private static final List<MdcThreadPoolExecutor> EXECUTOR_LIST = new ArrayList<>();
/**
* Monitor Thread pool periodically.
*/
private final static ScheduledExecutorService scheduledExecutorService =
new ScheduledThreadPoolExecutor(1, r -> {
final Thread t = new Thread();
// daemon thread won't block main thread
t.setDaemon(true);
t.setName("MDC Thread Monitor");
t.setPriority(Thread.MIN_PRIORITY);
return t;
});
static {
scheduledExecutorService.scheduleAtFixedRate(() -> EXECUTOR_LIST.forEach(MdcThreadPoolExecutor::monitor), 0, 1, TimeUnit.MINUTES);
}
private static void monitor(MdcThreadPoolExecutor pool) {
if (!pool.isTerminated()) {
log.info("MDC Thread Pool[{}]: core:{}, maximum:{}, largest:{}, poolSize:{}, active:{}, queue:{}",
pool.getName(), pool.getCorePoolSize(), pool.getMaximumPoolSize(), pool.getLargestPoolSize(),
pool.getPoolSize(), pool.getActiveCount(), pool.getQueue().size());
}
}
/**
* Pool where task threads take MDC from the submitting thread.
*/
public static MdcThreadPoolExecutor newWithInheritedMdc(String name, int corePoolSize, int maximumPoolSize, long keepAliveTime,
TimeUnit unit, BlockingQueue<Runnable> workQueue) {
return new MdcThreadPoolExecutor(name, null, corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}
/**
* Pool where task threads take fixed MDC from the thread that creates the pool.
*/
public static MdcThreadPoolExecutor newWithCurrentMdc(String name, int corePoolSize, int maximumPoolSize, long keepAliveTime,
TimeUnit unit, BlockingQueue<Runnable> workQueue) {
return new MdcThreadPoolExecutor(name, MDC.getCopyOfContextMap(), corePoolSize, maximumPoolSize, keepAliveTime, unit,
workQueue);
}
/**
* Pool where task threads always have a specified, fixed MDC.
*/
public static MdcThreadPoolExecutor newWithFixedMdc(String name, Map<String, String> fixedContext, int corePoolSize,
int maximumPoolSize, long keepAliveTime, TimeUnit unit,
BlockingQueue<Runnable> workQueue) {
return new MdcThreadPoolExecutor(name, fixedContext, corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}
private MdcThreadPoolExecutor(String name, Map<String, String> fixedContext, int corePoolSize, int maximumPoolSize,
long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
this.fixedContext = fixedContext;
useFixedContext = (fixedContext != null);
this.name = name;
synchronized (EXECUTOR_LIST) {
EXECUTOR_LIST.add(this);
}
}
@Override
protected void terminated() {
super.terminated();
log.info("MDC Thread Pool[{}]: TERMINATED");
synchronized (EXECUTOR_LIST) {
EXECUTOR_LIST.remove(this);
}
}
private Map<String, String> getContextForTask() {
return useFixedContext ? fixedContext : MDC.getCopyOfContextMap();
}
/**
* All executions will have MDC injected. {@code ThreadPoolExecutor}'s submission methods ({@code submit()} etc.)
* all delegate to this.
*/
@Override
public void execute(Runnable command) {
super.execute(wrap(command, getContextForTask()));
}
private static Runnable wrap(final Runnable runnable, final Map<String, String> context) {
return () -> {
Map<String, String> previous = MDC.getCopyOfContextMap();
if (context == null) {
MDC.clear();
} else {
MDC.setContextMap(context);
}
try {
runnable.run();
} finally {
if (previous == null) {
MDC.clear();
} else {
MDC.setContextMap(previous);
}
}
};
}
}
