Resource limits

By default a container may use all the memory and all the CPU of the server. --memory and --cpus cap it, so one runaway service cannot take the whole server down.

How it works

--memory 512m sets a hard limit enforced by the kernel's cgroups; --cpus 1.5 caps CPU time. In Compose, use mem_limit and cpus, or deploy.resources.limits. docker stats shows each container's usage against its limit.

What breaks

A limit below what the app really needs gets it killed over and over (exit code 137). Set limits from measured usage plus a margin, and keep their sum under the server's memory, with room left for the system.

In a terminal

docker run -d --name api --memory 512m --cpus 1 orders-api
docker stats --no-stream

See it break, then fix it

Write the Dockerfile or the compose file, type the docker commands, and watch a simulated server run them through reboots, upgrades and traffic. Free to start.

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