HttpClient在一千次http请求后，总是会出现UnknownHostException

在使用HttpClient version 3.1.0.访问web页面的时候，在请求1000-2000次后，总是会出现UnknownHostException。
1.连接是正常关闭的。
2.HttpConnectionManager使用的是MultiThreadedHttpConnectionManager。
3.如果不涉及大量的图片，异常会在2000-8000次后出现这个异常。
4.初步怀疑是因为线程太多，等待造成。
不知大家有什么好的解决方案没有？
Caused by: java.net.UnknownHostException:
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:195) ~[na:1.6.0_43]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) ~[na:1.6.0_43]
at java.net.Socket.connect(Socket.java:529) ~[na:1.6.0_43]
at java.net.Socket.connect(Socket.java:478) ~[na:1.6.0_43]
at java.net.Socket.<init>(Socket.java:375) ~[na:1.6.0_43]
at java.net.Socket.<init>(Socket.java:249) ~[na:1.6.0_43]
at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:80) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:122) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1361) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:387) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397) ~[commons-httpclient-3.1.jar:na]
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323) ~[commons-httpclient-3.1.jar:na]
at com.jiwu.reaper.http.HttpClientManager.execute(HttpClientManager.java:120) ~[classes/:na]
... 20 common frames omitted

关注一下，还发现还有这样的问题

我也遇到过，没找到原因。调用端重试，服务端做幂等，算是能解决这个问题。

可以迁移只httpclient4  在这版本无此问题，之前因为遇到这个问题，才迁移只版本4

1. try this: System.setProperty("http.keepAlive","false");

if not working, try this:
2. do not close streams and ((HttpURLConnection)conn).disconnect()