The Overhead of Docker Run
First published on Medium on 10/11/2016.
We use Docker a lot. Like a lot, lot. While we love it for a lot of things, it still has a lot of room for improvement. One of those areas that could use improvement is the startup/teardown time of running a container.
Table of Contents
Related Reading: The pros-and-cons of docker
The Test
To test the overhead of running a Docker container, I made a script that compares execution times for various docker run options vs not using Docker at all. The script that I’m running is a simple hello world shell script that consists of the following:
echo "Hello World!"
The base Docker image is the official Alpine linux image plus the script above.
4 Things to Compare
- As a baseline, the first measurement is sans Docker. This is just running the hello.sh script directly.
- The second measure is just docker run IMAGE.
- The third measure adds the “rm” flag to remove the container after execution.
- The final one is to use docker start instead of run, so we can see the effect of reusing an already created container.
Docker for Mac
Server Version: 1.12.2-rc1
Running: ./hello.sh avg: 5.897752ms Running: docker run treeder/hello:sh avg: 988.098391ms Running: docker run — rm treeder/hello:sh avg: 999.637832ms Running: docker start -a reuse avg: 986.875089ms
(Note: looks like using Ubuntu as a base image is slightly faster than Alpine, in the 10–50ms range).
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Docker on Ubuntu
Server Version: 1.12.1
Running: ./hello.sh avg: 2.139666ms Running: docker run treeder/hello:sh avg: 391.171656ms Running: docker run — rm treeder/hello:sh avg: 396.385453ms Running: docker start -a reuse each: 340.793602ms
Results
As you can see from the results above, using Docker adds nearly a full second to the execution time of our script on Mac and ~390ms on Linux (~175x slower than running the script without Docker).
Now, this may not be much of an issue if your script/application runs for a long period of time, but it is certainly an issue if you run short-lived programs.
Try it yourself
Feel free to try running the script on your system and share the results! You can find everything you need here:https://github.com/treeder/dockers/tree/master/hello
Just clone that repo, cd into the hello directory and run:
go run time.go
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