scout/usage: add --docker flag to scout usage tool

[jasonhawkharris]

Test plan

Tested manually with healthy and unhealthy docker sourcegraph instance.

[eseliger]

I'm missing a bit of context here, what is the relation of this tool and the docker stats command?
This is what it would give:

 ~ docker stats --no-stream --no-trunc --all
CONTAINER ID                                                       NAME                 CPU %     MEM USAGE / LIMIT     MEM %     NET I/O       BLOCK I/O   PIDS
4844cb8c6fd16f57f69290197f8eaa6b8f4e7a340148a8ba3bc3ad1c4139b972   syntax-highlighter   0.00%     34.92MiB / 7.765GiB   0.44%     1.51kB / 0B   0B / 0B     14
6696bf320826e206b910284e2f4b8b0bf8d2d45105a343d347383cdbbaf2c89e   lago-front           0.00%     0B / 0B               0.00%     0B / 0B       0B / 0B     0

[jasonhawkharris]

@eseliger long and short of it is that I just haven't found a way to get cpu/memory usage from the goclient for the docker API. The dockerstats library solves this issue, and does so quicker than if I were to just wrap the command in an exec function.

[eseliger]

Is performance a huge problem here? The docker stats command also allows structured output in JSON. Just trying to avoid reinventing the wheel here if there's something suitable already that would work similarly, there are likely edge-cases that docker CLI people have thought of already that we haven't.
If there's good reasons for going with this completely custom implementation, happy to take that, just making sure we consider our options and make sure we need to write and maintain as much code as needed and as little as possible :)

[jasonhawkharris]

Performance is not a huge problem here. You're right.

Found a way to do this with the docker client. Requesting re-review.

[eseliger]

Code LGTM, just to clarify - what is this going to be used for that docker stats could not do? Is this for envs where docker cli isn't available? Is this meant to generate a more elaborate report?

[jasonhawkharris]

src scout usage works on a Kubernetes deployment and returns current usages. The usage command, in particular, is more useful for Kubernetes deployments.

However, adding the --docker flag will allow it to work on docker deployments as well. It's less needed because of the docker stats command, but I wanted to have it as an option for our support/TA/CE folks because this command takes you to a TUI that allows the user to easily export this information and send it back to us.

Happy to hop on a call if you'd like to see this in real time.

[eseliger]

Thanks, that's the bit of context I was missing :)