AWS CodeDeploy AppSpec Script for Service Validation

This script is designed to be used within an AWS CodeDeploy AppSpec file to validate the health of a service before proceeding with a deployment. It ensures that the application is responsive and ready to accept traffic.

Script Overview

The script performs the following actions:

• Sets the script to exit immediately if a command exits with a non-zero status.
• Generates a timestamp for logging purposes.
• Continuously checks the health endpoint of the application (assumed to be http://localhost:8000/health) until it receives a successful response.
• Logs a message indicating that the application is passing health checks.
• Writes the current deployment ID to a version file, which can be useful for tracking deployed versions.

Usage in AppSpec

This script is typically placed in the AfterInstall or ApplicationStart hooks of your AppSpec file. Here's a conceptual example:

hooks:
  AfterInstall:
    - location: scripts/validate_service.sh
      timeout: 300
      runas: root
  ApplicationStart:
    - location: scripts/start_application.sh
      timeout: 300
      runas: root

External Resources

• AWS CodeDeploy AppSpec Reference
• HTTP Status Code 200 OK
• Bash 'set -ex' Explanation

Code Snippet

#!/usr/bin/env bash
set -ex
DATESTAMP="$(date +%FT%H:%m)"

# Verify if the service is healthy
while ! curl -sf http://localhost:8000/health; do sleep 5; done

# log
echo "[${DATESTAMP}] application passing health checks"

# write current version to disk
echo "${DEPLOYMENT_ID}" > /opt/codedeploy-agent/deployment-root/${DEPLOYMENT_GROUP_ID}/.version