How to persist data in a dockerized DynamoDB using volumes

Question

My docker compose file has two containers and looks like this

  version: '3'

  services:
     dynamodb:
       image: amazon/dynamodb-local
       ports: 
         - '8000:8000'
       networks:
         - testnetwork

     audit-server:
         image: audit-dynamo
         environment:
         DYNAMO_URL: 'http://0.0.0.0:8000'
         command: node app.js
         ports: 
           - '3000:3000'
         depends_on: 
           - dynamodb
         # restart: always

         networks:
           - testnetwork

  networks:
    testnetwork:

My goal is to mount local data to some volume. currently losing data on docker-compose down

Answer 1

So that image uses by default in-memory dynamodb (what you can find by running docker inspect on that image)

"CMD [\"-jar\" \"DynamoDBLocal.jar\" \"-inMemory\"]"

So if you want to keep your data, you need to do something like this in your docker-compose:

version: '3'

volumes: 
  dynamodb_data:

services:
  dynamodb:
    image: amazon/dynamodb-local
    command: -jar DynamoDBLocal.jar -sharedDb -dbPath /home/dynamodblocal/data/
    volumes:
     - dynamodb_data:/home/dynamodblocal/data
    ports:
     - "8000:8000"

Answer 2

To preserve data across docker installations create volume using docker.

docker volume create --driver local --opt type=none \
    --opt device=/var/opt/dynamodb_data --opt o=bind dynamodb_data

use external option:

version: "3"
volumes: 
  dynamodb_data:
    external: true
services:
  dynamodb-local:
    image: amazon/dynamodb-local
    command: ["-jar", "DynamoDBLocal.jar", "-sharedDb", "-dbPath", "/home/dynamodblocal/data"]
    volumes:
      - dynamodb_data:/home/dynamodblocal/data