Tutorials › Docker › Healthchecks

Healthchecks

5 min read Quiz at the end

Add healthchecks so Docker and Compose know when a service is ready before routing traffic.

Container Healthchecks

# In Dockerfile
HEALTHCHECK --interval=30s --timeout=10s --retries=3     CMD curl -f http://localhost:3000/health || exit 1

# In docker-compose.yml
services:
  api:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      start_period: 10s
      retries: 3

# depends_on with health condition
depends_on:
  api:
    condition: service_healthy

# Check status
docker inspect --format={{.State.Health.Status}} mycontainer

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Topic Quiz · 2 questions

Test your understanding before moving on

1. What exit code makes a healthcheck report unhealthy?

💡 Any non-zero exit code from the healthcheck command marks the container as unhealthy.

2. What does start_period do in a healthcheck?

💡 start_period gives slow-starting containers time to initialise before health failures are counted.

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Healthchecks

Container Healthchecks

Test your understanding before moving on