现象：队列在抛出异常后不再进行消费，但是线程仍然存活
查看线程状态
- 进入docker
- jps -l查看pid
- jstack -l pid
"pool-1-thread-1" #37 prio=5 os_prio=0 cpu=100.93ms elapsed=125.98s tid=0x00007fc530ccd800 nid=0x39 waiting on condition [0x00007fc4dc9b9000]
java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park(java.base@11.0.2/Native Method)
- parking to wait for <0x0000000095cc6b80> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(java.base@11.0.2/LockSupport.java:194)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(java.base@11.0.2/AbstractQueuedSynchronizer.java:2081)
at org.apache.http.pool.PoolEntryFuture.await(PoolEntryFuture.java:138)
at org.apache.http.pool.AbstractConnPool.getPoolEntryBlocking(AbstractConnPool.java:306)
at org.apache.http.pool.AbstractConnPool.access$000(AbstractConnPool.java:64)
at org.apache.http.pool.AbstractConnPool$2.getPoolEntry(AbstractConnPool.java:192)
at org.apache.http.pool.AbstractConnPool$2.getPoolEntry(AbstractConnPool.java:185)
at org.apache.http.pool.PoolEntryFuture.get(PoolEntryFuture.java:107)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:276)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:263)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:190)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:88)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107)
at com.XXXXXX.taiji.common.api.ExternalAPIClient.lambda$callWithTracer$0(ExternalAPIClient.java:81)
at com.XXXXXX.taiji.common.api.ExternalAPIClient$$Lambda$374/0x00000001005cd440.run(Unknown Source)
at com.XXXXXX.taiji.common.tracer.TracerSupport.lambda$new$0(TracerSupport.java:6)
at com.XXXXXX.taiji.common.tracer.TracerSupport$$Lambda$310/0x000000010045d840.with(Unknown Source)
at com.XXXXXX.taiji.common.tracer.TracerSupport.lambda$tracer$1(TracerSupport.java:17)
at com.XXXXXX.taiji.common.tracer.TracerSupport$$Lambda$331/0x00000001004d6440.run(Unknown Source)
at com.XXXXXX.taiji.common.cat.CatExternalAPITracer.with(CatExternalAPITracer.java:22)
at com.XXXXXX.taiji.common.cat.CatExternalAPITracer.with(CatExternalAPITracer.java:11)
at com.XXXXXX.taiji.common.tracer.TracerSupport.lambda$tracer$2(TracerSupport.java:16)
at com.XXXXXX.taiji.common.tracer.TracerSupport$$Lambda$312/0x000000010045d040.with(Unknown Source)
at com.XXXXXX.taiji.common.api.ExternalAPIClient.callWithTracer(ExternalAPIClient.java:79)
at com.XXXXXX.taiji.common.api.ExternalAPIClient.executeWithJSON(ExternalAPIClient.java:72)
at com.XXXXXX.taiji.qingniao.service.factory.WeiWangSendService.sendMsg(WeiWangSendService.java:76)
at com.XXXXXX.taiji.qingniao.service.factory.AbstractSendService.sendSMS(AbstractSendService.java:63)
at com.XXXXXX.taiji.qingniao.service.MessageService.deal(MessageService.java:286)
at com.XXXXXX.taiji.qingniao.redismq.SendMessageRedisQueue.lambda$start$0(SendMessageRedisQueue.java:74)
at com.XXXXXX.taiji.qingniao.redismq.SendMessageRedisQueue$$Lambda$315/0x000000010045a440.accept(Unknown Source)
at com.XXXXXX.taiji.common.redismq.RedisQueueWorker.lambda$kickit$1(RedisQueueWorker.java:85)
at com.XXXXXX.taiji.common.redismq.RedisQueueWorker$$Lambda$372/0x00000001005ce440.run(Unknown Source)
at java.util.concurrent.Executors$RunnableAdapter.call(java.base@11.0.2/Executors.java:515)
at java.util.concurrent.FutureTask.run(java.base@11.0.2/FutureTask.java:264)
at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@11.0.2/ThreadPoolExecutor.java:1128)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@11.0.2/ThreadPoolExecutor.java:628)
at java.lang.Thread.run(java.base@11.0.2/Thread.java:834)
waiting on condition
通过jstack -l pid发现pool-1-thread-1这个线程有问题
线程状态为“waiting on condition”：
说明它在等待另一个条件的发生，来把自己唤醒，或者干脆它是调用了 sleep(N)。
此时线程状态大致为以下几种：
java.lang.Thread.State: WAITING (parking)：线程挂起，一直等那个条件发生；
java.lang.Thread.State: TIMED_WAITING (parking或sleeping)：定时的，那个条件不到来，也将定时唤醒自己。
at org.apache.http.pool.PoolEntryFuture.await
由at org.apache.http.pool.PoolEntryFuture.await可知，是http连接池被拿光了连接数
推测可能是由于http的连接资源没有正确释放导致的
配合业务日志打印的异常“api xxxx respond status code 503”
推测可能是http请求过程中抛出异常导致了没有正确close
代码排查
this.tracer().with(traceKey, req, () -> {
try {
var res = this.client.execute(req);
var code = res.getStatusLine().getStatusCode();
if (code < 200 || code >= 300) {
throw GlobalErrors.API_STATUS_ERROR.args(path, code);
}
var output = new ByteArrayOutputStream();
var input = res.getEntity().getContent();
IOUtils.copy(input, output);
input.close();
String content = output.toString();
if (content.isEmpty()) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, "http body is empty");
}
holder.value(content);
} catch (IOException e) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, e.getMessage(), e);
}
});
res、output、input一共三个
OutputStream和InputStream的close方法是一个空方法，交给jvm的gc来处理，不关闭也没事
this.client.execute(req)返回的是一个CloseableHttpResponse(接口)，源码比较复杂，最终找到res的close方法调用了releaseConnection
public void close() throws IOException {
this.releaseConnection(false);
}
那么应该是Response没有close导致的
AutoCloseable
java的输入输出流、各种Connection，都继承了AutoCloseable接口
看了下AutoCloseable接口的源码，注释比较长，从注释可知它的出现是为了更好的管理资源，准确说是资源的释放，当一个资源类实现了该接口close方法，在使用try-catch-resources语法创建的资源抛出异常后，JVM会自动调用close 方法进行资源释放，当没有抛出异常正常退出try-block时候也会调用close方法。
try-catch-resources语法
try-catch-resources语法自jdk1.7新增，在try的()内部创建资源，创建的资源在退出try-block时候会自动调用该资源的close方法
示例：
public class AutoCloseableDemo {
public static void main(String[] args) {
try (AutoCloseableApp app = new AutoCloseableApp(); AutoCloseableApp2 app2 = new AutoCloseableApp2()) {
System.out.println("--执行main方法--");
throw new RuntimeException("--exception--");
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
System.out.println("--finally--");
}
}
public static class AutoCloseableApp implements AutoCloseable {
@Override
public void close() throws Exception {
System.out.println("--close1--");
}
}
public static class AutoCloseableApp2 implements AutoCloseable {
@Override
public void close() throws Exception {
System.out.println("--close2--");
}
}
}
输出：
--执行main方法--
--close2--
--close1--
--exception--
--finally--
- 由带资源的try语句管理的资源必须是实现了AutoCloseable接口的类的对象
- 在try代码中声明的资源被隐式声明为fianl
- 通过使用分号分隔每个声明可以管理多个资源
- 执行顺序：close-catch-finally
- 有多个资源时，关闭顺序为资源声明顺序的反序
修改后的代码
this.tracer().with(traceKey, req, () -> {
try (var res = this.client.execute(req)) {
var code = res.getStatusLine().getStatusCode();
if (code < 200 || code >= 300) {
throw GlobalErrors.API_STATUS_ERROR.args(path, code);
}
var output = new ByteArrayOutputStream();
var input = res.getEntity().getContent();
IOUtils.copy(input, output);
String content = output.toString();
if (content.isEmpty()) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, "http body is empty");
}
holder.value(content);
} catch (IOException e) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, e.getMessage(), e);
}
});
问题来了，为什么不抛出异常的时候不close也没事？
this.tracer().with(traceKey, req, () -> {
try {
var res = this.client.execute(req);
var code = res.getStatusLine().getStatusCode();
var output = new ByteArrayOutputStream();
var input = res.getEntity().getContent();
IOUtils.copy(input, output);
if (code < 1000) {
throw GlobalErrors.API_STATUS_ERROR.args(path, code);
}
String content = output.toString();
if (content.isEmpty()) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, "http body is empty");
}
holder.value(content);
} catch (IOException e) {
throw GlobalErrors.API_ACCESS_ERROR.args(path, e.getMessage(), e);
}
});
以上这段代码，一定会抛出异常throw GlobalErrors.API_STATUS_ERROR.args(path, code)，res也没有close，但是并不会出现线程park的情况。
当把IOUtils.copy(input, output)这一行代码挪到抛出异常下面时，线程会park
查看了一下IOUtils.copy的源码，也没发现什么特殊之处
还需要继续研究
