我正在使用Apache HttpClient 4与REST API进行通信,并且大部分时间我都在进行冗长的PUT操作 . 由于这些可能发生在不稳定的Internet连接上,我需要检测连接是否中断并且可能需要重试(使用恢复请求) .
为了在现实世界中尝试我的例程,我开始了PUT操作,然后我翻转了笔记本电脑的Wi-Fi开关,导致任何数据流立即完全中断 . 然而,它需要一个很长的时间(可能是5分钟左右),直到最终抛出SocketException .
How can I speed up to process? I'd like to set a timeout of maybe something around 30 seconds.
更新:
为了澄清,我的请求是PUT操作 . 因此,在很长一段时间(可能是几小时)内,唯一的操作是write()操作,并且没有读操作 . 有一个timeout setting for read() operations,但我找不到一个用于写操作 .
我正在使用自己的实体实现,因此我直接写入一个OutputStream,一旦Internet连接中断,它几乎会立即阻塞 . 如果OutputStreams有一个超时参数,那么我可以写 out.write(nextChunk, 30000);
我自己可以检测到这样的问题 . 其实我试过了:
public class TimeoutHttpEntity extends HttpEntityWrapper {
public TimeoutHttpEntity(HttpEntity wrappedEntity) {
super(wrappedEntity);
}
@Override
public void writeTo(OutputStream outstream) throws IOException {
try(TimeoutOutputStreamWrapper wrapper = new TimeoutOutputStreamWrapper(outstream, 30000)) {
super.writeTo(wrapper);
}
}
}
public class TimeoutOutputStreamWrapper extends OutputStream {
private final OutputStream delegate;
private final long timeout;
private final ExecutorService executorService = Executors.newSingleThreadExecutor();
public TimeoutOutputStreamWrapper(OutputStream delegate, long timeout) {
this.delegate = delegate;
this.timeout = timeout;
}
@Override
public void write(int b) throws IOException {
executeWithTimeout(() -> {
delegate.write(b);
return null;
});
}
@Override
public void write(byte[] b) throws IOException {
executeWithTimeout(() -> {
delegate.write(b);
return null;
});
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
executeWithTimeout(() -> {
delegate.write(b, off, len);
return null;
});
}
@Override
public void close() throws IOException {
try {
executeWithTimeout(() -> {
delegate.close();
return null;
});
} finally {
executorService.shutdown();
}
}
private void executeWithTimeout(final Callable<?> task) throws IOException {
try {
executorService.submit(task).get(timeout, TimeUnit.MILLISECONDS);
} catch (TimeoutException e) {
throw new IOException(e);
} catch (ExecutionException e) {
final Throwable cause = e.getCause();
if (cause instanceof IOException) {
throw (IOException)cause;
}
throw new Error(cause);
} catch (InterruptedException e) {
throw new Error(e);
}
}
}
public class TimeoutOutputStreamWrapperTest {
private static final byte[] DEMO_ARRAY = new byte[]{1,2,3};
private TimeoutOutputStreamWrapper streamWrapper;
private OutputStream delegateOutput;
public void setUp(long timeout) {
delegateOutput = mock(OutputStream.class);
streamWrapper = new TimeoutOutputStreamWrapper(delegateOutput, timeout);
}
@AfterMethod
public void teardown() throws Exception {
streamWrapper.close();
}
@Test
public void write_writesByte() throws Exception {
// Setup
setUp(Long.MAX_VALUE);
// Execution
streamWrapper.write(DEMO_ARRAY);
// Evaluation
verify(delegateOutput).write(DEMO_ARRAY);
}
@Test(expectedExceptions = DemoIOException.class)
public void write_passesThruException() throws Exception {
// Setup
setUp(Long.MAX_VALUE);
doThrow(DemoIOException.class).when(delegateOutput).write(DEMO_ARRAY);
// Execution
streamWrapper.write(DEMO_ARRAY);
// Evaluation performed by expected exception
}
@Test(expectedExceptions = IOException.class)
public void write_throwsIOException_onTimeout() throws Exception {
// Setup
final CountDownLatch executionDone = new CountDownLatch(1);
setUp(100);
doAnswer(new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) throws Throwable {
executionDone.await();
return null;
}
}).when(delegateOutput).write(DEMO_ARRAY);
// Execution
try {
streamWrapper.write(DEMO_ARRAY);
} finally {
executionDone.countDown();
}
// Evaluation performed by expected exception
}
public static class DemoIOException extends IOException {
}
}
这有点复杂,但在单元测试中效果很好 . 它也可以在现实生活中使用,除了 HttpRequestExecutor
捕获第127行中的异常并尝试关闭连接 . 但是,当尝试关闭连接时,它首先尝试刷新再次阻塞的连接 .
我可能能够深入挖掘HttpClient并弄清楚如何防止这种刷新操作,但它已经是一个不太漂亮的解决方案,而且它将变得更糟 .
UPDATE :
看起来这不能在Java级别上完成 . 我可以在另一个级别上做吗? (我正在使用Linux) .
3 回答
Java阻塞I / O不支持写操作的套接字超时 . 您完全受操作系统/ JRE的支配,可以解除阻塞写操作阻塞的线程 . 此外,此行为往往是特定于OS / JRE .
这可能是考虑使用基于非阻塞I / O(NIO)的HTTP客户端(例如Apache HttpAsyncClient)的合法案例 .
您可以使用RequestConfig配置套接字超时:
当您进行呼叫时,只需分配新配置即可 . 例如,
有关重新启动超时配置的更多信息,here有一个很好的解释 .
她是我遇到的链接之一
connection eviction policy
:here我想你可能想看看这个 .