Resource monitoring per container in Docker - Commands & Configuration

Introduction

Sometimes, you want to see how much memory or CPU each container is using. This helps you find slow or heavy containers so you can fix or stop them.

When you want to check if a container is using too much memory and slowing down your server

When you want to compare CPU usage between different containers running on the same machine

When you need to find out if a container is stuck or not responding because it uses too many resources

When you want to monitor resource use during testing to optimize your app's performance

When you want to keep your server healthy by stopping containers that use too many resources

Commands

This command shows the current CPU, memory, and network usage for all running containers once. It helps you quickly see resource use without continuous updates.

Terminal

docker stats --no-stream

Expected Output

CONTAINER ID   NAME          CPU %     MEM USAGE / LIMIT     MEM %     NET I/O           BLOCK I/O         PIDS

b1c2d3e4f5g6   my-app        2.35%     50.3MiB / 1GiB        4.91%     1.2MB / 1.1MB     0B / 0B           12

c7d8e9f0g1h2   db-server     0.00%     120MiB / 2GiB         5.86%     500kB / 450kB     0B / 0B           20

→

--no-stream - Show resource usage only once instead of updating continuously

This command shows live resource usage for the container named 'my-app'. It updates every second so you can watch how usage changes over time.

Terminal

docker stats my-app

Expected Output

CONTAINER ID   NAME          CPU %     MEM USAGE / LIMIT     MEM %     NET I/O           BLOCK I/O         PIDS

b1c2d3e4f5g6   my-app        2.50%     51.0MiB / 1GiB        5.00%     1.3MB / 1.2MB     0B / 0B           12

b1c2d3e4f5g6   my-app        2.70%     52.1MiB / 1GiB        5.09%     1.4MB / 1.3MB     0B / 0B           12

b1c2d3e4f5g6   my-app        2.60%     51.5MiB / 1GiB        5.04%     1.5MB / 1.4MB     0B / 0B           12

This command shows the memory limit set for the container 'my-app'. It helps you know if the container has a memory cap.

Terminal

docker inspect --format='{{.Name}} uses {{.HostConfig.Memory}} bytes memory limit' my-app

Expected Output

/my-app uses 1073741824 bytes memory limit

→

--format - Customize output to show only specific information

Key Concept

If you remember nothing else from this pattern, remember: docker stats shows real-time resource use per container to help you monitor and manage your apps.

Common Mistakes

Running 'docker stats' without specifying --no-stream when you only want a snapshot

The command keeps running and updating, which can clutter your terminal and confuse you

Add the --no-stream flag to get a single snapshot of resource usage

Trying to monitor a container that is not running

Docker stats only works on running containers and will show an error or no output

Make sure the container is running before using docker stats

Not checking container resource limits with docker inspect

You might think a container can use unlimited memory or CPU, but limits may be set and affect performance

Use docker inspect with --format to see resource limits set on containers

Summary

Use 'docker stats --no-stream' to get a one-time snapshot of resource use for all running containers.

Use 'docker stats container-name' to watch live resource use for a specific container.

Use 'docker inspect --format' to check resource limits set on a container.