Capture image id in benchmark executions

[coryan]

The image ID is not captured by the benchmark driver. We should try to. Basically if /proc/self/cgroup has the right information in it, you can determine that you are running inside a container:

For example:

$ cat /proc/self/cgroup 
11:hugetlb:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
10:blkio:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
9:freezer:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
8:pids:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
7:net_cls,net_prio:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
6:memory:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
5:devices:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
4:cpuset:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
3:cpu,cpuacct:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
2:perf_event:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40
1:name=systemd:/docker/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40

If that is the case, and if the container is running with --volume /var/run/docker.sock:/var/run/docker.sock you can query the container attributes using:

curl --unix-socket /var/run/docker.sock http:/v1.26/containers/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40/json

That returns a lot more information than one may want, but we should be able to get the data using something like:

curl --unix-socket /var/run/docker.sock http:/v1.26/containers/256299b017cc4f6240db3ac640d2ea4d9306da724b7be428ef844e1ac48a1d40/json | grep -o '"Id":"[a-f0-9]*"'