Compose Dependency Ordering

Intermediate10 min

Configure service startup order in Docker Compose using depends_on with health check conditions to prevent race conditions.

Prerequisites

-Docker Compose installed

Steps

Define health checks for dependency services

Ensure database and cache services have health checks so dependent services know when they are ready.

$ cat <<'EOF' services: db: image: postgres:16-alpine healthcheck: test: ["CMD-SHELL", "pg_isready -U postgres"] interval: 5s timeout: 5s retries: 5 EOF

Configure depends_on with conditions

Make the API service wait until the database is healthy before starting.

$ cat <<'EOF' services: api: image: myapp:latest depends_on: db: condition: service_healthy redis: condition: service_healthy EOF

Without the condition, depends_on only waits for the container to start, not for the service inside to be ready.

Verify startup order

Start the stack and verify services come up in the correct order.

$ docker compose up -d && docker compose ps

Full Script

full-script.sh

#!/bin/bash
# Compose Dependency Ordering Check
set -euo pipefail

echo "=== Service Status and Dependencies ==="
docker compose ps --format 'table {{.Name}}\t{{.Status}}'

echo ""
echo "=== Compose Config Validation ==="
docker compose config --quiet && echo "Config is valid" || echo "Config has errors"

echo ""
echo "=== Startup Order Tips ==="
echo "1. Add healthcheck to every database/cache service"
echo "2. Use depends_on with condition: service_healthy"
echo "3. Set appropriate start_period for slow-starting services"
echo "4. Consider retry logic in application code as a fallback"

FAQ

Discussion

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#!/bin/bash # Compose Dependency Ordering Check set -euo pipefail echo "=== Service Status and Dependencies ===" docker compose ps --format 'table {{.Name}}\t{{.Status}}' echo "" echo "=== Compose Config Validation ===" docker compose config --quiet && echo "Config is valid" || echo "Config has errors" echo "" echo "=== Startup Order Tips ===" echo "1. Add healthcheck to every database/cache service" echo "2. Use depends_on with condition: service_healthy" echo "3. Set appropriate start_period for slow-starting services" echo "4. Consider retry logic in application code as a fallback"