有這么一個(gè)線程類（extends Thread）run方法中有如下代碼
while(true) {
Socket socket = null;
GZIPInputStream gzis = null;
ObjectInputStream ois = null;
try {
socket = new Socket(IP, PORT);
gzis = new GZIPInputStream(socket.getInputStream());
ois = new ObjectInputStream(gzis);
Map<Integer, Object> result = (Map<Integer, Object>) ois.readObject();
doSomeBuziness(result);
} catch(Exception e) {
log.error(...);
} finally {
// clean work here
sleep(1000);
}
}
即線程啟動(dòng)后 每隔1秒 從Socket服務(wù)端接收數(shù)據(jù) 然后對接收到的數(shù)據(jù)做些業(yè)務(wù)邏輯處理
突然發(fā)現(xiàn)數(shù)據(jù)好像一直沒有更新 通過jstack命令 可知該線程已經(jīng)掛起了
"Thread-5" daemon prio=10 tid=0x00002b54800cd000 nid=0x691f runnable [0x00002b5433be7000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:152)
at java.net.SocketInputStream.read(SocketInputStream.java:122)
at java.util.zip.InflaterInputStream.fill(InflaterInputStream.java:238)
at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:158)
at java.util.zip.GZIPInputStream.read(GZIPInputStream.java:116)
問：
為什么線程都掛起了 還是 RUNNABLE 狀態(tài)呢？ 不是BLOCKED狀態(tài)呢？
這種掛起的底層機(jī)制是什么？ 如對應(yīng)什么系統(tǒng)命令 和下面等待鎖釋放導(dǎo)致線程掛起的區(qū)別是什么(底層機(jī)制有什么不同)
static synchronized void foo() {
Thread.sleep(10*60*1000);
}
如有一個(gè)加了同步塊的foo方法 兩個(gè)線程都去調(diào)用這個(gè)foo方法 其中一個(gè)會(huì)被阻塞
"pool-1-thread-2" prio=5 tid=0x00007f9ed00a5000 nid=0x5503 waiting for monitor entry [0x00007000079c7000]
java.lang.Thread.State: BLOCKED (on object monitor)
at com.demo.LockDemo.foo(LockDemo.java:24)
- waiting to lock <0x00000007aae446d0> (a java.lang.Class for com.demo.LockDemo)
at com.demo.LockDemo$1.run(LockDemo.java:15)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
針對Socket read的這種掛起 不想重啟應(yīng)用 有什么辦法可以人工顯式結(jié)束這種掛起嗎？
at java.net.SocketInputStream.socketRead0(Native Method)
如 通過命令行顯式殺死這個(gè)socket 這樣的話可以拋個(gè)異常被捕獲 然后休眠一秒 可以繼續(xù)往下走了 不會(huì)卡住不動(dòng)了
3 回答
慕村225694
TA貢獻(xiàn)1880條經(jīng)驗(yàn) 獲得超4個(gè)贊
你應(yīng)該好好JDK關(guān)于線程狀態(tài)的文檔java.lang.Thread.State
public enum State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* Thread state for a runnable thread. A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
* <ul>
* <li>{@link Object#wait() Object.wait} with no timeout</li>
* <li>{@link #join() Thread.join} with no timeout</li>
* <li>{@link LockSupport#park() LockSupport.park}</li>
* </ul>
*
* <p>A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called <tt>Object.wait()</tt>
* on an object is waiting for another thread to call
* <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
* that object. A thread that has called <tt>Thread.join()</tt>
* is waiting for a specified thread to terminate.
*/
WAITING,
/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
* <ul>
* <li>{@link #sleep Thread.sleep}</li>
* <li>{@link Object#wait(long) Object.wait} with timeout</li>
* <li>{@link #join(long) Thread.join} with timeout</li>
* <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
* <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
* </ul>
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}RUNNABLE狀態(tài)指的是，線程正在JVM中運(yùn)行，但是它們需要等待來自操作系統(tǒng)的資源，比如說CPU資源,這里當(dāng)然是網(wǎng)絡(luò)資源，所以它本該就是RUNNABLE的。BLOCKED狀態(tài)，專門指的是線程正在等待內(nèi)置鎖的過程。WAITING說明線程正在等待另一個(gè)線程的特定操作。
想要結(jié)束這種等待，要么給與線程所需要的網(wǎng)絡(luò)資源（這種控制不了），要么直接關(guān)閉Socket,或者調(diào)用interrupt方法（其實(shí)底層也是關(guān)閉Socket,可以看看interrupt的API文檔）。
哆啦的時(shí)光機(jī)
TA貢獻(xiàn)1779條經(jīng)驗(yàn) 獲得超6個(gè)贊
我覺得設(shè)置 socket 的超時(shí)時(shí)間比較合適, 如
socket = new Socket(IP, PORT);
socket.setSoTimeout(1000 * 60); // 讀操作的超時(shí)時(shí)間為 60 秒如此, 當(dāng) socket read 在超過 60秒沒有收到數(shù)據(jù)時(shí), 將拋出 SocketException 異常.
另外, 在 try finally 中應(yīng)釋放資源(關(guān)閉 socket).
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