[Hawkular-dev] Docker image size does matter

[Heiko W.Rupp]

On 1 Feb 2017, at 12:29, Jiri Kremser wrote:

> base image with JRE 8 and Alpine linux: 76.8 MB

Yes, alpine is only 3-4 MB that is great.

> I also removed
> 9.2M  /opt/jboss/wildfly/docs

Makes sense.


> What also helped was squashing all the image layers into 1. This makes 
> the
> download faster and possibly the image smaller. When applying 
> docker-squash
> [1] to the current h-services image it saves ~50megs

This is a bit of a false friend as docker pull only transfers layers it
does not yet have.

E.g

$ docker pull pilhuhn/hawkular-services:0.30.0.Final
0.30.0.Final: Pulling from pilhuhn/hawkular-services
08d48e6f1cff: Already exists
664e6a3041e6: Already exists
2f8461e7022b: Already exists
9500f4548bd3: Already exists
69e2e5217a47: Already exists
cf95509fd4ad: Downloading [======>                                       
      ] 10.75 MB/89.61 MB

So what you say is true for the first download, but afterwards all
the base layers of wf + jdk + ... are present. With stripping
into 1 layer there is no chance of caching.
Situation of course changes when the base layer is updated


> I am aware that this probably wont fly with some RH policy that we 
> should
> base our SW on Fedora/RHEL base OS images, but I am gonna use them for
> development and because I often run out of space because of Docker.

I like those alpine images and use them for private stuff,
but for Hawkular upstream I think we should use something
that is close for downstream so minimise the moving parts.