Container metrics collection in Docker - Mini Project: Build & Apply

Container Metrics Collection

📖 Scenario: You are managing a small set of Docker containers running different services on your local machine. You want to collect basic metrics like CPU and memory usage for each container to monitor their performance.

🎯 Goal: Build a simple Docker setup that collects and stores container metrics in a structured way for easy querying and monitoring.

📋 What You'll Learn

Create a Docker Compose file with two containers running simple services

Add a configuration to enable metrics collection for these containers

Write a command or script to query and display the metrics

Ensure the metrics data is stored or accessible for later analysis

💡 Why This Matters

🌍 Real World

Monitoring container resource usage is essential for maintaining healthy and efficient applications in production environments.

💼 Career

DevOps engineers and system administrators often need to collect and analyze container metrics to optimize performance and troubleshoot issues.

1

Create Docker Compose with two containers

Create a file named docker-compose.yml with two services: webapp running the image nginx:latest and db running the image mysql:5.7. Both should restart always.

Docker

# Your code here

Need a hint?

Use the services key to define two containers with the exact names and images.

2

Enable metrics collection configuration

In the docker-compose.yml, add labels under both webapp and db services with the key com.example.metrics set to enabled.

Docker

version: '3.8'
services:
  webapp:
    image: nginx:latest
    restart: always
    # Add labels here
  db:
    image: mysql:5.7
    restart: always
    # Add labels here

Need a hint?

Use the labels key under each service to add the metrics label.

3

Write a command to collect container metrics

Write a shell command that uses docker stats --no-stream --format to display the container name, CPU percentage, and memory usage for containers with the label com.example.metrics=enabled. Store the output in a variable called metrics.

Docker

version: '3.8'
services:
  webapp:
    image: nginx:latest
    restart: always
    labels:
      com.example.metrics: enabled
  db:
    image: mysql:5.7
    restart: always
    labels:
      com.example.metrics: enabled

# Write the docker stats command and assign to metrics variable
# Your code here

Need a hint?

Use docker stats with --no-stream and --filter to get metrics only once for labeled containers.

4

Store metrics output to a file

Add a command to save the metrics variable content into a file named container_metrics.txt.

Docker

version: '3.8'
services:
  webapp:
    image: nginx:latest
    restart: always
    labels:
      com.example.metrics: enabled
  db:
    image: mysql:5.7
    restart: always
    labels:
      com.example.metrics: enabled

metrics=$(docker stats --no-stream --format "{{.Name}} {{.CPUPerc}} {{.MemUsage}}" --filter "label=com.example.metrics=enabled")

# Save metrics to a file
# Your code here

Need a hint?

Use echo with double quotes and redirect output to the file.