Name:
tcpcopy
It is an online TCP duplication tool and can be used for testing (using netlink and raw sockets).
Description:
It can help you find bugs without deploying your server software on your production servers.
It can also be used to do smoke testing against your products.
For example, when you want to migrate your web server from Apache to Nginx, tcpcopy can help you test
it. Apache is running online, while tcpcopy can copy the TCP flows from Apache to Nginx. To Nginx, the
TCP flows are just forwarding to it. This will not affect Apache at all except cost a little network
bandwidth and CPU load.
Scenarios:
1) Distributed stress testing
Use tcpcopy to copy real-world data to stress test your server software. Bugs that only can be
produced in high-stress situations can be found.
2) Hot backup
It is very suitable for backup tasks if connections are short-lived. The request loss ratio is
quite low (e.g. 0.000001).
3) Online testing
Prove the new system is stable and find bugs that only occur in the real world.
4) Benchmark
Do performance benchmark. For instance, you can use tcpcopy to compare the performance of Apache
and Nginx.
Usage:
1) Install
a) download the source code from github:
git clone https://github.com/wangbin579/tcpcopy
b) ./configure
c) make
d) make install
2) Run:
a) on the source host (root privilege is required):
./tcpcopy local_ip1[:local_ip2:...] local_port remote_ip remote_port
b) on the target host (root privilege is required):
modprobe ip_queue # if not running
iptables -I OUTPUT -p tcp --sport port -j QUEUE # if not set
./interception
Example:
Suppose there are two online hosts, 1.2.3.13 and 1.2.3.14. And 1.2.3.148 is the target host (similar to
the online hosts). Port 12321 is used both as local port and remote port. We use tcpcopy to test if
1.2.3.148 can process 2X requests than a host can serve.
Here we use tcpcopy to perform the above test task.
1) on the target host (1.2.3.148)
# modprobe ip_queue # if not run up
# iptables -I OUTPUT -p tcp --sport 12321 -j QUEUE # if not set
# ./interception
2) online host (1.2.3.13)
# ./tcpcopy 1.2.3.13 12321 1.2.3.148 12321
3) online host(1.2.3.14)
# ./tcpcopy 1.2.3.14 12321 1.2.3.148 12321
CPU load and memory usage is as follows:
1.2.3.13:
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
1.2.3.14:
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
1.2.3.148:
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:
1.2.3.13:
$ grep 'Tue 11:08' access_0913_11.log | wc -l
89316, 1489 reqs/sec
1.2.3.14:
$ grep 'Tue 11:08' access_0913_11.log | wc -l
89309, 1488 reqs/sec
1.2.3.148:
$ grep 'Tue 11:08' access_0913_11.log | wc -l
178175, 2969 reqs/sec
request loss ratio:
(89316 + 89309 - 178175) / (89316 + 89309) = 0.25%
Clearly, the target host can process 2X of requests a source host can serve.
How is the CPU load? Well, tcpcopy on online host 1.2.3.13 used 12.3%, host 1.2.3.14
used 14%, while interception on the target host consumed about 17%. We can see that
the CPU load is low here, and so is the memory usage.
Note:
1) It is tested on Linux only (kernal 2.6 or above).
2) Tcpcopy may lose packets hence lose requests.
3) If you use tcpcopy to duplicate local requests, please keep lo MTU not more than 1500.
4) Interception (tcpcopy server) is single-threaded now.
5) Root privilege is required.
6) Long-lived requests (such as uploading a large file) does not work well (no retransmission
when sending packets to the target test server)
7) Check error.log if you encounter some problem and feel free to report it to us
([email protected] or [email protected]).