Here’s a complete tutorial on docker stats, covering what it does, a comprehensive list of examples, and use cases.

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What is docker stats?

docker stats is a Docker command that provides real-time resource usage statistics for running containers, such as CPU, memory, network I/O, and block I/O. It’s useful for monitoring the performance of your containers and diagnosing resource-related issues.

Key Features:

• Displays live resource usage for one or more containers.
• Helps in performance monitoring and resource optimization.
• Works similarly to the top command in Linux but is container-specific.
• Supports customized output and filtering.

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Basic Syntax

docker stats [OPTIONS] [CONTAINER...]

Options:

• --all, -a: Show stats for all containers, not just running ones.
• --format: Customize the output using Go templates.
• --no-stream: Show only a single snapshot of stats, instead of continuous updates.
• --no-trunc: Do not truncate output (show full container IDs and names).

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Examples of docker stats

1. Show Real-Time Stats for All Running Containers

docker stats

Example Output:

CONTAINER ID   NAME        CPU %     MEM USAGE / LIMIT   MEM %     NET I/O   BLOCK I/O   PIDS
a1b2c3d4e5f6   my_app      2.50%     512MiB / 1GiB      50.00%    1.2kB/1kB  0B/0B       5
b2c3d4e5f67g   my_db       0.75%     256MiB / 512MiB    50.00%    5kB/5kB   0B/0B       3

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2. Show Stats for a Specific Container

docker stats my_app

This displays live stats only for my_app.

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3. Show a Single Snapshot of Stats

docker stats --no-stream

This displays container stats once and exits.

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4. Show Stats for Multiple Containers

docker stats my_app my_db

Displays real-time stats for both my_app and my_db.

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5. Show Stats for All Containers (Including Stopped)

docker stats --all

This includes stats for stopped containers, showing 0% CPU and memory usage for them.

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6. Customize Output with --format

docker stats --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"

Example Output:

NAME       CPU %     MEM USAGE
my_app     1.25%     512MiB / 1GiB
my_db      0.50%     256MiB / 512MiB

This formats the output to show only container name, CPU percentage, and memory usage.

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7. Show Full Container IDs and Names

docker stats --no-trunc

Prevents truncation of container IDs and names.

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8. Monitor Resource Usage in a Script

#!/bin/bash
while true; do
  docker stats --no-stream >> resource_usage.log
  sleep 60
done

This script logs resource usage for all containers every minute.

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9. Monitor Specific Resource Usage for a Container

docker stats my_web_container --no-stream --format "CPU: {{.CPUPerc}}, Memory: {{.MemUsage}}"

Example Output:

CPU: 2.00%, Memory: 300MiB / 1GiB

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10. Combine with Other Docker Commands

Restart a container if its memory usage exceeds a threshold:

if [[ $(docker stats my_app --no-stream --format "{{.MemPerc}}" | cut -d'%' -f1) > 80 ]]; then
  docker restart my_app
fi

This checks if the container’s memory usage is above 80% and restarts it if true.

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Use Cases for docker stats

1. Performance Monitoring

• Continuously monitor CPU, memory, and I/O usage for critical services.
• Identify resource bottlenecks in multi-container environments.

2. Debugging Resource-Related Issues

• Diagnose high memory or CPU usage that could cause containers to slow down or crash.
• Example: Find containers with abnormal CPU spikes.

3. Capacity Planning

• Use historical stats to plan resource allocation for your containers.
• Example: Increase memory allocation for a database container if its usage frequently reaches the limit.

4. Automation and Scripting

• Automate actions like scaling services, restarting containers, or triggering alerts based on resource thresholds.

5. Security and Incident Response

• Monitor suspicious behavior in containers (e.g., unexpected CPU or network spikes).
• Example: Detect a compromised container generating unusual network traffic.

6. CI/CD Pipelines

• Use docker stats to monitor resource usage during builds and tests to avoid exceeding CI system limits.

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List of Common docker stats Commands

Command	Description
docker stats	Show real-time stats for all running containers
docker stats my_container	Show stats for a specific container
docker stats --no-stream	Show a single snapshot of stats
docker stats --all	Show stats for all containers (including stopped)
docker stats --format "table {{.Name}} {{.CPUPerc}} {{.MemUsage}}"	Customize output
docker stats --no-trunc	Show full container IDs and names

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Best Practices for Using docker stats:

1. Monitor resource usage regularly to prevent performance issues.
2. Use --format for clarity in automation and scripts.
3. Combine with alerting tools (like Prometheus or Grafana) for automated resource monitoring.
4. Set resource limits (--memory, --cpus) for containers to avoid unexpected resource consumption.
5. Analyze historical trends for capacity planning.

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Common Errors and Solutions

1. “No such container”
   → Ensure the container exists and is running. Use docker ps to verify.
2. Stats show 0% CPU and memory usage
   → This is expected for paused or stopped containers. Use docker stats --all to confirm their status.
3. Output is too large
   → Use --format to filter and display only the necessary fields.

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Combining docker stats with Other Tools

1. Monitor with Prometheus and Grafana for advanced visualization and alerting.
2. Integrate with custom scripts for automated scaling or resource management.

Example: Logging Resource Usage

docker stats --no-stream --format "CPU: {{.CPUPerc}}, Mem: {{.MemUsage}}" >> usage.log

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