Host resources vs Pod resources
GeertJohan opened this issue · comments
I'm running the collector as a sidecar container in a zalando/postgres-operator managed postgres cluster.
It seems that the reported machine specs (cpu, memory) are those of the host. I think it makes more sense if the collector would report the cpu and memory for the container it's managing. Or maybe the collector could have override flags so that I can tell it what the correct values are.
Right now I get a warning about shared_buffers because the host machine has a lot more memory than the pod. So the shared_buffers ratio when comparing with the host is wrong. But it's actually set to 25% when compared with the containers's max memory.
@GeertJohan Yes - thats a good point, and a known issue in a sense.
We'll have to adjust the logic we use for retrieving OS statistics to be cgroup-aware, i.e. reading from the /sys/fs/cgroup folder. The library we currently use for reading system statistics (gopsutil) has some support for this, but it seems the author would like to remove this at some point: shirou/gopsutil#996 (comment) -- the library also does not seem to correctly support ECS containers: shirou/gopsutil#1061
Ideally we would utilize a different library for getting the cgroup statistics, but a quick search did not turn up something usable, so we'll have to investigate a bit more, or write our own. Thoughts welcome, in case you are familiar with the Go libraries around this.
Overall better Kubernetes support is on our near-future roadmap, and I'll include a reference to this issue in our planning document. We'll update this issue once we make progress / implement a solution.