Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT什么都不做? [英] Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT does nothing?
问题描述
我从HttpClient获得奇怪的行为,参数CoreConnectionPNames.CONNECTION_TIMEOUT设置为1.
我希望HttpGet请求失败,抛出连接超时异常但它们成功了。这似乎是不合理的,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.
我正在使用的httpclient版本可以在这个pom.xml中看到
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>
以下是代码:
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。
How is this possible? Thank you.
推荐答案
我所使用过的所有JVM中的超时有效粒度大约是15- 30毫秒。即使超时设置为1个套接字I / O,连接请求通常也会成功,如果它们的时间少于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.
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