Tcpcopy,an online request replication tool fit for nginx

[wangbin579]

An example:
    Suppose 13 and 14 are online machines, 148 is a target machine which
is similar to 
    the online machines, and 12321 is used both as local port and remote
port. We 
    use tcpcopy to test if 148 can endure two times of current online
stress.
    
    Using tcpcopy to perform the above test task.
    the target machine(148)
       # modprobe ip_queue (if not run up)
       # iptables -I OUTPUT -p tcp --sport 12321 -j QUEUE (if not set)
       # ./interception
    online machine(13):
       # ./tcpcopy xx.xx.xx.13 12321 xx.xx.xx.148 12321
    online machine(14):
       # ./tcpcopy xx.xx.xx.14 12321 xx.xx.xx.148 12321

    Cpu load and memory usage are as follows:
        13 cpu:
           11124 adrun 15 0 193m 146m 744 S 18.6 7.3 495:31.56
asyn_server
           11281 root 15 0 65144 40m 1076 S 12.3 2.0 0:47.89 tcpcopy
        14 cpu:
           16855 adrun 15 0 98.7m 55m 744 S 21.6 2.7 487:49.51
asyn_server
           16429 root 15 0 41156 17m 1076 S 14.0 0.9 0:33.63 tcpcopy
        148 cpu :
           25609 root 15 0 76892 59m 764 S 49.6 2.9 63:03.14
asyn_server
           20184 root 15 0 5624 4232 292 S 17.0 0.2 0:52.82
interception

    Access log analysis:
        13 online machine: grep 'Tue 11:08' access_0913_11.log |wc -l
:89316,  1489 reqs/sec
        14 online machine: grep 'Tue 11:08' access_0913_11.log |wc -l
:89309,  1488 reqs/sec
        148 test  machine: grep 'Tue 11:08' access_0913_11.log |wc -l
:178175, 2969 reqs/sec
        request loss rate:
           (89316+89309-178175)/(89316+89309)=0.25%

    From the above, we can see that the target machine can endure two
times of current 
    online stress.
    
    What about the cpu load ?
    tcpcopy on online machine 13 occupies 12.3% of cpu load, tcpcopy on
online 14 
    occupies 14% and interception on target machine 148 occupies 17%. We
can see 
    that the cpu load is very low here, and so is the memory usage.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,217680,217734#msg-217734