I was looking at some ideas for re-implementing an SMTP server that I work on for my day job. As I was reading about a netty example implementation called smptd on github. I saw something very interesting. He was testing his code using a command from Postfix called smtp-source. I was immediately interested. I pulled his example code and updated it for a newer version of netty (3.10.6) and started it up. I then pulled an Ubuntu image from Docker Hub and started it up. Once it was started, I used apt-get to install Postfix. The result was that I had my own little test environment up in about 5 minutes. So I tested the code from the smtpd project on my Windows 10 Pro machine (HP Pavillion Wave for those who are interested) using the smtp-source command from a Docker container. Here were my results.
time smtp-source -c -d -l 32000 -m 10000 -N -s 100 10.0.1.9:2525
real 0m12.543s
user 0m0.410s
sys 0m2.640s
The results were very interesting on a non-server class machine, or environment. It handled 10,000 email requests with 100 simultaneous connections in 12 seconds. I was impressed. time is a built in function on UNIX machines. The real time is the time that was used to process the requests. This was just a really good demonstration of Docker, containers, Postfix tools, and netty.