Lambda Server

Dgraph Lambda is a component that allows you to execute custom business logic using JavaScript/TypeScript functions within your GraphQL API. It's part of Dgraph's GraphQL implementation and enables you to extend the auto-generated GraphQL API with custom resolvers.

note

Dgraph lambda is an optional server, only used for GraphQL API.

Running with Docker

To run a Dgraph Lambda server with Docker:

docker run -it --rm -p 8686:8686 -v /path/to/script.js:/app/script/script.js -e DGRAPH_URL=http://host.docker.internal:8080 dgraph/dgraph-lambda

note

host.docker.internal doesn't work on older versions of Docker on Linux. You can use DGRAPH_URL=http://172.17.0.1:8080 instead.

Adding libraries

If you would like to add libraries to Dgraph Lambda, use webpack --target=webworker to compile your script.

Working with TypeScript

You can import @slash-graphql/lambda-types to get types for addGraphQLResolver and addGraphQLMultiParentResolver.

Dgraph Alpha

To set up Dgraph Alpha, you need to define the --graphql superflag's lambda-url option, which is used to set the URL of the lambda server. All the @lambda fields will be resolved through the lambda functions implemented on the given lambda server.

For example:

dgraph alpha --graphql lambda-url=http://localhost:8686/graphql-worker

Then test it out with the following curl command:

curl localhost:8686/graphql-worker -H "Content-Type: application/json" -d '{"resolver":"MyType.customField","parent":[{"customField":"Dgraph Labs"}]}'

Docker settings

If you're using Docker, you need to add the --graphql superflag's lambda-url option to your Alpha configuration. For example:

    command: /gobin/dgraph alpha --zero=zero1:5180 -o 100 --expose_trace --trace ratio=1.0
      --profile_mode block --block_rate 10 --logtostderr -v=2
      --security whitelist=10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 --my=alpha1:7180
      --graphql lambda-url=http://lambda:8686/graphql-worker

Next, you need to add the Dgraph Lambda server configuration, and map the JavaScript file that contains the code for lambda functions to the /app/script/script.js file. Remember to set the DGRAPH_URL environment variable to your Alpha server.

Here's a complete Docker example that uses the base Dgraph image and adds Lambda server support:

services:
  dgraph:
    image: dgraph/standalone:latest
    environment: 
      DGRAPH_ALPHA_GRAPHQL: "lambda-url=http://dgraph_lambda:8686/graphql-worker"
    ports:
      - "8080:8080"
      - "9080:9080"
      - "8000:8000"
    volumes:
      - dgraph:/dgraph

  dgraph_lambda:
    image: dgraph/dgraph-lambda:latest

    ports:
      - "8686:8686"
    environment:
      DGRAPH_URL: http://dgraph:8080
    volumes:
      - ./gql/script.js:/app/script/script.js:ro

volumes:
  dgraph: {}