Monday, April 28, 2014

Stress Testing with Siege and Bombard, know your limits

I couldn't find a clear quick intro on getting siege and bombard in action, so I'm writing one here.

Siege is a load testing and benchmarking utility that has been available for quite a while, It allows you to hit your web application on a specific url (or a set of urls in a file) with specific concurrency and size settings.  siege summarizes the measures of the test outcome including:

  • Transaction rate (requests/sec)
  • Actual concurrency (even if you hit with 200 concurrent connections, your server might be responding with just 80)
  • Average, longest and shortest response time

triggering 200 concurrent users, each hitting the url twice

siege -c200 -r2


Transactions:         400 hits
Availability:      100.00 %
Elapsed time:       38.44 secs
Data transferred:        0.26 MB
Response time:       10.09 secs
Transaction rate:       10.41 trans/sec
Throughput:        0.01 MB/sec
Concurrency:      104.96
Successful transactions:         400
Failed transactions:           0
Longest transaction:       34.19
Shortest transaction:        0.52

Siege is available in most repos and can be installed directly on ubuntu/debian via

apt-get install siege

However, in order for POST requests to work normally, I'd recommend installing the latest version (currently 3.0.5) from source

tar zxvf siege-3.0.5.tar.gz
cd siege-3.0.5/
./configure && make && sudo make install

Similar tools exist, mainly ab of apache,  but ab is very basic compared to the flexibility of siege

Using siege is great for a single test, but you'll need to run it several times with different parameters in order to be able to understand your limits. and there comes the handy wrapper, bombard.

Bombard is a wrapper for siege that allows you to start your load testing with certain parameters and increase the load (concurrency) incrementally. and it draws charts that let's you see how your server reacts.  plotting makes things more clear and gives you a better sense of your server current limits.

Installing bombard requires dependencies:
  • GD2 perl module
    sudo apt-get install libgd-graph-perl
  • Chart-2.x
    tar zxf  Chart-2.4.6.tar.gz && cd Chart-2.4.6 && \
    perl Makefile.PL && make && make test  && sudo make install
Then you can install bombard from the source

git clone
cd bombard
make && sudo make install

Now you can check all options through bombard -h

let's try experimenting out site:
Let's start with:
  • starting concurrency 50
  • increment 10
  • runs 10 times  (so it will try 50, 60, 70, 80, ..., 140)
  • each run will take 1 minute
Note: Bombard expects the absolute path of the file, it will not work with relative paths

bombard  -f /home/me/bombard-test-urls.txt -i10 -r10 -s50 -t1

From both graphs we can see that the transactions rate increases as we increase test concurrency. but it nearly saturates at concurrency 80.  The response time starts at nearly half a second, and remains so as we increase the load. until we reach 80 concurrency.  then it increases. the increase here is not from our web application itself, It is actually from having the requests buffer at the web server and application.

The two graphs indicate that our setup is able to handle up to 80 concurrent requests decently. then the performance will degrade as the load increases.

If you find this useful, please share your experience via comments, or get it touch with @modsaid

Friday, April 18, 2014

Linode finally back to the new baseline of VPS Hosting

2 days ago Linode finally announced their new VPS Hosting offering with doubling the RAM and moving to Fast SSD storage

SSD Storage will allow much faster operations for both setup operations, compilation and ongoing running services.

And the new memory upgrade is considered a drop in the pricing to the half, since people can now use the same server Ram with half the price they used to pay.

The smallest Instance offered by linode is now the 2GB Instance with $20/mo as stated in their pricing list:

Plan RAM SSD CPU Transfer Outbound
Linode 2G 48 GB 2 cores 3 TB 250 Mbps $0.03/hr | $20/mo
Linode 4G 96 GB 4 cores 4 TB 500 Mbps $0.06/hr | $40/mo
Linode 8G 192 GB 6 cores 8 TB 1 Gbps $0.12/hr | $80/mo
Linode 16G 384 GB 8 cores 16 TB 2 Gbps $0.24/hr | $160/mo
Linode 32G 768 GB 12 cores 20 TB 4 Gbps $0.48/hr | $320/mo
Linode 48G 1152 GB 16 cores 20 TB 8 Gbps $0.72/hr | $480/mo
Linode 64G 1536 GB 20 cores 20 TB 10 Gbps $0.96/hr | $640/mo
Linode 96G 1920 GB 20 cores 20 TB 10 Gbps $1.44/hr | $960/mo

This is considered a good Getting Back in Track  for linode.  both offering has been there from DigitalOcean for more than 15 months. Causing lots of users to test waters with it and others to actually migrate to digital ocean.

Now the cost of the 2G Instance and larger instances is now the same for both hosting providers.
However, Digital Ocean still offers smaller setup starting from 512MB Server for $5/mo  which can be more suitable for lots of users.  Digital Ocean offering since the beginning of 2013 and still today:

Plan RAM SSD CPU Transfer Price
512MB 20GB 1 Core 1TB $5/mo
1GB 30GB 1 Core 2TB $10/mo
2GB 40GB 2 Core 3TB $20/mo
4GB 60GB 2 Core 4TB $40/mo
8GB 80GB 4 Core 5TB $80/mo

Linode, however still have an edge for better processor offering in some of the package, and is still known for their reliable support.