Background

Kubernetes collects lots of metrics data regarding the resources usage within the cluster (cpu, memory, network, disk). In this article, we will be focusing on the various memory metrics that are collected by cAdvsior and which ones cause OOMkill whenever we apply memory limits to the pods.

Kubernetes Metrics For Memory

When you execute inside your container and navigate to the following directory, you will find all the container’s memory information you may need. The usage, limits, cache, number of times your container got OOMKilled, e.t.c will all be found in this directory:

cd /sys/fs/cgroups/memory/

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The following control files will be gotten whenever the content of this directory is listed out:

root@test-8589C7679b-bfjrn:/sys/fs/cgroup/memory## ls
cgroup.clone_children	memory.kmem.limit_in_bytes	memory.kmem.tcp.Usage_in_bytes memory.oom_control 	memory.use_hierarchy
cgroup.event_control  memory.kmem.max_usage_in_bytes memory.kmem.usage_in_bytes  	memory.pressure_level notify_on_release
cgroup.procs  memory.kmem.slabinfo  memorylimit_in_bytes  memory.soft_limit_in_bytes 	tasks
memory.failcnt   	memory.kmem.tcp.failcnt  	memory.max_usage_in_bytes  	memory.stat
memory.force_empty 	memory.kmem.tcp.limit_in_bytes memory.move_charge_at_immigrate memory.swappiness
memory.kmen.failcnt	memory.kmem.tcp.max_usage_in_bytes	memory.numa_stat  	memory.usage_in_bytes

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Each file contains a piece of information about the memory. You can read more about them here.

#devops #kubernetes #write-for-cloud-native #memory metrics