The DevOps toolkit 2.3 book by Victor Farcic goes into some detail on this.
What You Should Understand
- You as a developer specify whatever requests/limits you like initially.
- These values have no baring on reality.
- In order to get "real" values, you must monitor your application's real resource usage.
- This is best done through a monitoring tool like prometheus, instana, datadog etc.
- E.g. in instana, I can see that I have 512MB set up for a pod's requests, 2G for its limits, but the pod only has one container currently taking 57MB.
- But I can't just use 60MB as a value now... I need to load test my application and see how it behaves under real/stressed circumstances.
- Then you review these values and you can adjust the requests/limits accordingly.
Determine Usage Without a Monitoring Tool
You can use some kubectl commands to get these values as a one off (it's annoying at scale). Here is an example of a different app I have running.
Notice that requests/limits are set to 1/4-2 CPUs and 4G-8G memory. But the container is really using almost no CPU and 1.198G memory. If I load tested this and those values did not move up, I would need to change them. But I have load tested it and know that they would go up towards these realistic requests/limits, so it's okay.
$ kubectl describe pod -n gazelle gazelle-ws-0-0-1-6d67cffcf-lvlhk
$ kubectl top pod gazelle-ws-0-0-1-6d67cffcf-lvlhk -n gazelle --containers
POD NAME CPU(cores) MEMORY(bytes)
gazelle-ws-0-0-1-6d67cffcf-lvlhk gazelle-ws 5m 1198Mi