Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT 什么都不做? [英] Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT does nothing?
问题描述
我从参数 CoreConnectionPNames.CONNECTION_TIMEOUT 设置为 1 的 HttpClient 得到奇怪的行为.我希望 HttpGet 请求会失败,抛出连接超时异常,但它们成功了.这似乎不合理,因为它实际上意味着 TCP 握手在不到 1 毫秒内完成.
I get strange behavior from HttpClient with parameter CoreConnectionPNames.CONNECTION_TIMEOUT set to 1. I would expect that HttpGet request would fail, throwing connection timeout exception and yet they are successful. This seems irrational as it actually means that TCP handshake finished in less then 1 millisecond.
在这个 pom.xml 中可以看到我正在使用的 httpclient 版本是
The httpclient version I'm using as can be seen in this pom.xml is
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.0.1</version>
<type>jar</type>
</dependency>
代码如下:
import java.io.IOException;
import java.util.Random;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.CoreConnectionPNames;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;
public class TestNodeAliveness {
private static Logger log = Logger.getLogger(TestNodeAliveness.class);
public static boolean nodeBIT(String elasticIP) throws ClientProtocolException, IOException {
try {
HttpClient client = new DefaultHttpClient();
// The time it takes to open TCP connection.
client.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 1);
// Timeout when server does not send data.
client.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 5000);
// Some tuning that is not required for bit tests.
client.getParams().setParameter(CoreConnectionPNames.STALE_CONNECTION_CHECK, false);
client.getParams().setParameter(CoreConnectionPNames.TCP_NODELAY, true);
HttpUriRequest request = new HttpGet("http://" + elasticIP);
HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
if(entity == null) {
return false;
} else {
System.out.println(EntityUtils.toString(entity));
}
// Close just in case.
request.abort();
} catch (Throwable e) {
log.warn("BIT Test failed for " + elasticIP);
e.printStackTrace();
return false;
}
return true;
}
public static void main(String[] args) throws ClientProtocolException, IOException {
nodeBIT("google.com?cant_cache_this=" + (new Random()).nextInt());
}
}
这怎么可能?谢谢.
推荐答案
在我使用过的所有 JVM 中,超时的有效粒度约为 15-30 毫秒.即使超时设置为 1 个套接字 I/O 并且连接请求通常会成功,如果它们花费的时间少于 15-30 毫秒.
The effective granularity of time-outs in all JVMs I have worked with is approximately 15-30ms. Even if the timeout is set to 1 socket I/O and connect requests often succeed if they take less than 15-30ms.
这篇关于Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT 什么都不做?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!