使用wrk压力测试时，超过500连接就会出现500错误

[eddyyuen]

网关测试：

wrk -t10 -c500 -d30s -T30s http://127.0.0.1:9000/user/getuserinfo
Running 30s test @ http://127.0.0.1:9000/user/getuserinfo
10 threads and 500 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 43.87ms 51.35ms 781.09ms 95.91%
Req/Sec 1.32k 425.11 3.94k 73.91%
395668 requests in 30.09s, 95.09MB read
Socket errors: connect 0, read 18217, write 0, timeout 0
Requests/sec: 13150.42
Transfer/sec: 3.16MB

网关调用的webapi接口的测试，api本身没问题

$ wrk -t10 -c500 -d30s -T30s http://127.0.0.1:9050/user/getuserinfo
Running 30s test @ http://127.0.0.1:9050/user/getuserinfo
10 threads and 500 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 51.80ms 267.11ms 11.01s 97.92%
Req/Sec 4.26k 2.56k 18.50k 76.59%
1260011 requests in 30.10s, 258.35MB read
Requests/sec: 41861.31
Transfer/sec: 8.58MB

出错日志（详细日志写不了，会导致并发下降就不会出错）：

[2019/11/7 下午7:47:37] [Error] session 127.0.0.1:34530@17972 error 127.0.0.1:34530 send data completed process handler error Object reference not set to an instance of an object.!@object reference not set to an instance of an object.
at BeetleX.FastHttpApi.HttpApiServer.SendCompleted(ISession session, SocketAsyncEventArgs e)
at BeetleX.TcpServer.SendCompleted(SocketAsyncEventArgs e)

[beetlex-io]

这个错误会让人误解，在新版中已经调成Warring。主要触发的情况是发送完成后处理一些状态正好连接断开了引发了，实际上对服务没有影响。