Live Reloading with Compose Watch

Introduction

When working with lambda connectors, you'll often want to make quick edits to your custom business logic and don't want to go through the hassle of bringing down all your services, rebuilding them all, and restarting them. Instead you can leverage Compose Watch to listen for changes to your connector's entrypoint, and rebuild the connector on the fly.

Are you adding new functions or modifying the signature of existing functions?

The workflow described in the guide below helps when you're making changes to your connector's internal logic without altering the exposed function interfaces or metadata.

If you're adding new functions that will need to be exposed as commands in your application, or modifying existing functions' arguments or return types, you'll still need to regenerate your metadata and create a new build of your application.

Follow the steps here for more information.

Guide

Step 1. Update your start script

Open your .hasura/context.yaml file and locate your docker-start script.

Add the --watch flag to your start script:

docker-start:
  bash:
    HASURA_DDN_PAT=$(ddn auth print-access-token) PROMPTQL_SECRET_KEY=$(ddn auth print-promptql-secret-key) docker
    compose -f compose.yaml --env-file .env up --build --pull always --watch
  powershell:
    $Env:HASURA_DDN_PAT = ddn auth print-access-token; $Env:PROMPTQL_SECRET_KEY = ddn auth print-promptql-secret-key;
    docker compose -f compose.yaml --env-file .env up --build --pull always --watch

By adding the --watch flag to the docker compose up command, you're telling Docker to monitor the files specified in your service's develop section for changes. When changes are detected, Docker automatically triggers the action you configured (in this case, we'll use rebuild) without requiring you to manually stop and restart your services. This creates a much faster feedback loop while developing.

Step 2. Update your connector's compose.yaml

Add the following adjusting the path as necessary:

services:
  my_lambda_connector:
    build:
      context: .
      dockerfile: .hasura-connector/Dockerfile
    environment:
      HASURA_SERVICE_TOKEN_SECRET: $MY_LAMBDA_CONNECTOR_HASURA_SERVICE_TOKEN_SECRET
      OTEL_EXPORTER_OTLP_ENDPOINT: $MY_LAMBDA_CONNECTOR_OTEL_EXPORTER_OTLP_ENDPOINT
      OTEL_SERVICE_NAME: $MY_LAMBDA_CONNECTOR_OTEL_SERVICE_NAME
    extra_hosts:
      - local.hasura.dev:host-gateway
    ports:
      - 8203:8080
    develop:
      watch:
        - action: rebuild
          path: .

The develop section with watch tells Docker Compose which files or directories to monitor during development.

• path: . means "watch the entire context directory". You can narrow this down to the entrypoint file(s) if you want finer control. For example, you can isolate on the functions.ts file for the TypeScript connector or the ./functions directory for the Go connector.

• action: rebuild means that if any file changes within the watched path, Docker will automatically rebuild and restart the container. This setup ensures that your lambda connector is instantly rebuilt whenever you modify its code — speeding up iteration dramatically without manual intervention.

You can verify this by running ddn run docker-start from the root of your project and then making a modification to your lambda connector's logic. In your Docker logs, you should see the container for your connector being rebuilt and the changes you've made instantly reflected in your API.