Few times recently I've seen people using an HTTP benchmarking tool called wrk and decided to give it a try. It is a very cool instrument but didn't fit my use case perfectly. What I needed is to be able to redirect the connection through a web proxy and measure how much the proxy slows down things compared to hitting the web server directly with wrk. In other words - how fast is the proxy server.
How does a proxy work
I've examined the source code of two proxies (one in Python and another one in Go) and what happens is this:
- The proxy server starts listening to a TCP port
- A client (e.g. the browser) sends the request using an absolute URL (GET http://example.com/about.html)
- Instead of connecting directly to the web server behind example.com the client connects to the proxy
- The proxy server does connect to example.com directly, reads the response and delivers it back to the client.
Proxy in wrk
Luckily wrk supports the execution of Lua scripts so we can make a simple script like this:
init = function(args)
target_url = args[1] -- proxy needs absolute URL
end
request = function()
return wrk.format("GET", target_url)
end
Then update your command line to something like this: ./wrk [options] http://proxy:port -s proxy.lua -- http://example.com/about.html
This causes wrk to connect to our proxy server but instead issue GET requests for another URL.
Depending on how your proxy works you may need to add the Host: example.com header as well.
Now let's do some testing.
Comments !