On Thu, 29 Sep 2005, Rodre Ghorashi-Zadeh wrote:
I have a problem that I am hoping someone can help me with. I am currently
conducting some load testing on a test MySQL server that is destined to
replace our current production MySQL server. What I want to do is send our
current MySQL traffic, in real time, to the test MySQL server to measure the
load in comparison with our current production MySQL server.
Ok. But not at all trivial to do.
What I have done so far is setup port mirroring on the switch that is shared
by the Production MySQL server, the test MySQL server, and my Linux based
management station, with the Linux based managment station sniffing the
mirrored port of the Production MySQL server.
Ok.
I am able to see the MySQL traffic going to the production MySQL server using
tcpdump. For a next step what I want to be able to do is have iptables sniff
the port (I set the interface into promiscuous mode using ifconfig), grab all
packets that are destined for my Production MySQL server from the mirrored
port, rewrite the source IP address to be my Linux based management stations
IP address and rewrite the destination address to be my Test MySQL Servers IP
address.
This won't work. MySQL uses TCP and you can't mirror a TCP stream like
this.
I don't really care about the MySQL results returned to tthe Linux
based management station, they can go to /dev/null for all I care, but I want
to see the queries going through the Test MySQL server.
Ok. This simplifies things somewhat.
Can be done in two different manners. Both requires programming.
a) By sniffing and using a TCP stream reassembly tool and when a MySQL
query has been reassembled from the TCP stream send it to the test server.
Drawbacks is that TCP stream reassembly is not always reliable (packets
may have been dropped and a number of other complications).
b) Use a MySQL proxy via iptables REDIRECT and send each query to both
servers. This requires the intercepting box to be between the old server
and the network. Main drawback is that the source IP seen by the old
server will be changed to the address of the proxy.
Regards
Henrik
