Postgres vs Kubernetes container_memory_working_set_bytes

Jeremy Schneider provides an alternative:

Kubernetes metric container_memory_working_set_bytes is used for evicting/killing pods with too much memory use, especially if memory request < limit (don’t do this with Postgres). The metric is calculated from cgroups v2 memory.stat as current-inactive_file [source].

You’d assume it’s a good metric for memory usage in kubernetes. But with Postgres, this metric is very inaccurate for memory utilization and doesn’t tell you at all if you’re going to OOM crash your database.

Click through to understand what goes wrong, why it does, and what you can use instead.