Docker memory usage include cache, so is misleading

[julienmathevet]

Docker plugin get memory usage which include cache. So after some hours, reported memory usage is totaly wrong.

I check code I see you compute memory usage without cache but is not reported to any metrics

telegraf/plugins/inputs/docker/docker.go

Line 533 in c5fa672

mem := calculateMemUsageUnixNoCache(stat.MemoryStats)

Could we replace docker memory usage by a better memory usage or to add new metric like use_nocache ?

See also:

• Docker stats memory usage is misleading moby/moby#10824
• [Carry moby/moby#32777] Adjusted docker stats memory output docker/cli#80

[danielnelson]

Our code is based on the docker cli code, and we want the behavior be the same as upstream. I quickly looked at our code and it appears very similar to docker/cli#80 , Can you clarify which field is off?

telegraf/plugins/inputs/docker/docker.go

Lines 533 to 535 in c389a68

	mem := calculateMemUsageUnixNoCache(stat.MemoryStats)
	memLimit := float64(stat.MemoryStats.Limit)
	memfields["usage_percent"] = calculateMemPercentUnixNoCache(memLimit, mem)

[julienmathevet]

In docker cli they replaced memory by mem usage without cache. In telegraf we compute only mem usage without cache for mem percent computing (see https://github.com/docker/cli/pull/80/files )

[julienmathevet]

https://github.com/docker/cli/blob/f285fe67e916055ea61d45d6249c9946ee27b216/cli/command/container/stats_helpers.go#L107-L122

[julienmathevet]

#4383