开发JSAPI支付时，在统一下单接口中要求必传用户openid，openid是通过scope=snsapi_base的静默授权方式依次拿到code-》code换access_token（and openid）。

目前我们在用code换token环节（api.weixin.qq.com/sns/oauth2/access_token），遇到了接口错误率特别高的问题，最近7天平均每小时调用量在60左右，平均异常响应数量在15左右，错误率高达20%，错误表现都是read time out，异常堆栈如下

Caused by: org.apache.http.conn.ConnectTimeoutException: Connect to api.weixin.qq.com:443 [api.weixin.qq.com/121.51.166.37, api.weixin.qq.com/121.51.130.115] failed: Read timed out at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:143) at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:353) at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:380) at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236) 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 org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:55) at com.x.y.z.HttpUtils.httpCall(HttpUtils.java:157) ... 60 more Caused by: java.net.SocketTimeoutException: Read timed out at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:152) at java.net.SocketInputStream.read(SocketInputStream.java:122) at sun.security.ssl.InputRecord.readFully(InputRecord.java:442) at sun.security.ssl.InputRecord.read(InputRecord.java:480) at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:927) at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1312) at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1339) at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1323) at org.apache.http.conn.ssl.SSLConnectionSocketFactory.createLayeredSocket(SSLConnectionSocketFactory.java:394) at org.apache.http.conn.ssl.SSLConnectionSocketFactory.connectSocket(SSLConnectionSocketFactory.java:353) at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:134) ... 71 more