Add runtime metrics collection to the docker source

[binarylogic]

Docker has a runtime metrics feature. I'd like to collect this data, but I have a couple of important questions:

1. How would this overlap with a server_metrics source? A source that collect host level CPU, memory, disk, and network metrics.
2. Does it make sense to collect this data all in the same docker source, or should we rename the docker source to docker_logs so that we can add a new docker_metrics source?

[LucioFranco]

I think this should be integrated into a more general system level metrics collection source. My reasoning is because docker is basically a wrapper around cgroups which is a system level thing. Maybe we can find a way to expose the same metrics docker or no docker by just collecting general cgroup metrics.

[jszwedko]

Noting that a user requested this in Slack. Specifically the metrics exposed by http://api/containers/{container id or name}/stats Docker endpoint. They'd like to include the network stats as well.

[gaby]

Any updates on this? Can this be accomplished using host_metrics with cgroups?