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Adding database containers to the Application Template

Best practices for running your application's database in a container
This document should cover the basics for adding a database to your application.
A few caveats that come with running databases in containers:
  • Containers and pods in Kubernetes can be restarted, deleted, or moved at any time, so you should not rely on them for any critical services.
  • Containers are ephemeral and can move around, so it is vital to use a persistent storage volume so that restarting a container does not erase the database.
  • Kubernetes may start a container before the database is completely initialized or ready, so you should use readiness probes to ensure deployments wait for the database to be ready to receive traffic.
  • Passwords can be randomized and the database connections should be kept internal only so that external people cannot access the data or store their own data in your tables, even if it is a test database.

Postgres

Example Postgres Application Template

services:
- name: db
image: public.ecr.aws/lts/postgres:12-20.04_edge
volumes:
- type: persistent
name: db_data
mount_path: "/var/lib/postgresql/data"
ports:
- type: container_port
port: '5432'
readiness_probe:
exec:
command:
- psql
- "-h"
- localhost
- "-U"
- postgres
- "-c"
- SELECT 1
period_seconds: 2
timeout_seconds: 2
failure_threshold: 30
storage:
size: 10Gi

Example Postgres Environment Template

mapping:
DATABASE_URL: "postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@db/${POSTGRES_DB}"
services:
db:
- key: POSTGRES_PASSWORD
value: secretPassword
secret: true
- key: POSTGRES_USER
value: postgres
- key: POSTGRES_DB
value: postgres
- key: POSTGRES_HOST_AUTH_METHOD
value: trust
- key: PGDATA
value: "/var/lib/postgresql/data/pgdata"

MySQL

Example MySQL Application Template

- name: db
image: mysql:5.7
volumes:
- type: persistent
name: db_data
mount_path: "/var/lib/mysql"
ports:
- type: container_port
port: '5432'
liveness_probe:
exec:
command: ["mysqladmin", "ping"]
initial_delay_seconds: 30
period_seconds: 10
timeout_seconds: 5
failure_threshold: 10
readiness_probe:
exec:
# Check we can execute queries over TCP (skip-networking is off).
command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]
initial_delay_seconds: 5
period_seconds: 2
timeout_seconds: 1
failure_threshold: 30
storage:
size: 10Gi

Example MySQL Environment Template

services:
db:
- name: MYSQL_ALLOW_EMPTY_PASSWORD
value: "1"

Notes