using upstream in access phase and problem when having many connections

[Huy Phan]

Hi there,
I've done the nginx module that using upstream in access phase. It's working
properly with single request. When I use apache benchmark with 
requests = 10000 and concurrency = 500, the connection is always broken. 
I checked the log and see the message "client closed prematurely connection, 
so upstream connection is closed too while connecting to upstream .... "

This is the log file : 
30141#0: *33097 socket 9
30141#0: *33097 epoll add connection: fd:9 ev:80000005
30141#0: *33097 connect to 192.168.0.197:11211, fd:9 #33098
30141#0: *33097 http upstream connect: -2
30141#0: *33097 event timer add: 9: 60000:4022552673
30141#0: timer delta: 0
30141#0: posted events 00000000
30141#0: worker cycle
30141#0: epoll timer: 60000
30141#0: epoll: fd:6 ev:0005 d:08AC3490
30141#0: *33097 http run request: "/v/empty.flv?token=1234"
30141#0: *33097 http upstream check client, write event:0, "/v/empty.flv"
30141#0: *33097 http upstream recv(): 0 (115: Operation now in progress)
30141#0: *33097 client closed prematurely connection, so upstream connection is
closed too while connecting to upstream, client: 192.168.0.197, server:
localhost, request: "GET /v/empty.flv?token=1234 HTTP/1.0", upstream:
"memcached://192.168.0.197:11211", host: "192.168.0.197:7777"


The upstream connects to memcached server to authenticate the access.

Is that using upstream in access phase really a problem ? What should I do in
this case ?