Skip to content


Subversion checkout URL

You can clone with
Download ZIP
HTTP request spewer / load generator
C Tcl Shell
Fetching latest commit...
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.
src Whitespace fixes
INSTALL Initial import
WIP Initial import


README for spew

Spew is a HTTP request generator/spewer.

It's written to be fast and straight forward. It currently does no measurements and is pretty mean. But it's also fast.

It has the following features:

  • Generate HTTP requests to a server of your choice
  • Manipulate the Host-header
  • Tries to keep -p conns=X open connections at any given time
  • Sends -p reqs=X requests over each connection - IN ONE GO.
  • Ignores replies.
  • It's fast. Or more accurately: It does nothing.
  • It's single-threaded.
  • Native IPv6 support (it was easier than not to have it!)

As an example of speed, I was able to do 260-290 thousand requests per second against Varnish with spew using less than 10% cpu on my workstation at home (granted, that's a fast computer). On my laptop (i5 M520, 2.4GHz), spew easily does 30k-50k req/s with 3k-5k conn/s against a Varnish-server on localhost.

Version history

  • 0.4 - Adds -p rand=<int> option to provide a random factor to urls. Minor build tweaks.
  • 0.3 - Initial released version, sort of. 0.1, 0.2 and 0.3 were released on the same day.


  • If you want to test more than 1000-ish connections, you need to increase the ulimit for number of file descriptors.

  • Spew is relatively slow at opening connections. Or rather, opening connections is a slow task in general.

  • If you open connections too fast, you may want to set:

    sysctl net.ipv4.tcp_tw_recycle=1

    Otherwise you'll quickly run out of local ports.

  • Use spew -p url=/ -p otherparam=whatever -h param > ~/.config/spew to store your default options.

  • Run multiple spew-processes if you starve a single CPU thread. Let me know if this ever speeds things up for you!

Installation and usage


  • C compiler
  • make
  • awk
  • basic build stuff
  • Linux (because of epoll)

On ubuntu 12.04:

apt-get install build-essential automake tcl

From a repo: ./ && ./configure && make && make install From a tar-ball: ./configure && make && make install

Running: spew --help

If it's not in --help, it's not in spew. If it is, then someone got drunk, wohoo!

See WIP (Work In Progress) for day-to-day changes. The content of WIP as it was upon compile-time is usually printed upon startup.



The core part of spew, src/http.c, was hacked together in about 10 hours total by Kristian Lyngstøl for Varnish Software.

Everything else was then later borrowed from an old defunct project I had that only did parameter-parsin, config file support and all the typical boring stuff. That's why http.c and the rest is pretty different. If you find references to X-related stuff, let me know. They are old.

Something went wrong with that request. Please try again.