Creating actions¶

Table of contents

Introduction
Setup
Mutation type action
Query type action

Introduction¶

An action is a GraphQL query or mutation. You have to define the GraphQL type of the arguments that the query or mutation accepts and the GraphQL type of its response.

To create an action, you have to:

Define the query or mutation
Define the required types
Create a handler

Let’s look at examples for mutation and query type actions.

Setup¶

There is no setup required for defining actions via the console.

Install or update to the latest version of Hasura CLI.

You can either get started with an existing project or create a new project.

For a new project

hasura init

This will create a new project. You can set up your GraphQL engine endpoint (and admin secret if it exists) in the config.yaml.

Run hasura metadata export so that you get server’s metadata into the metadata/ directory.

For existing projects

Actions are supported only in the v2 config of the CLI. Check the config.yaml of your Hasura project for the version key.

If you see version: 1 (or do not see a version key), upgrade to version 2 by running:

hasura scripts update-config-v2

Run hasura metadata export so that you get server’s metadata into the metadata/ directory.

There is no setup required for defining actions via the actions metadata API.

Mutation type action¶

Let’s start with a mutation that accepts a username and password, and returns an access token. We’ll call this mutation login.

Step 1: Define your mutation and associated types
Step 2: Create the action handler
Step 3: Finish action creation
Step 4: Try it out

Step 1: Define your mutation and associated types¶

Start with defining the mutation and the required types. These types will reflect in the GraphQL schema.

Go to the Actions tab on the console and click on Create. This will take you to a page like this:

Define the action as follows in the Action Definition editor.

type Mutation {
  login (username: String!, password: String!): LoginResponse
}

In the above action, we called the returning object type to be LoginResponse. Define it in the New types definition as:

type LoginResponse {
  accessToken: String!
}

To create an action, run

hasura actions create login

This will open up an editor with metadata/actions.graphql. You can enter the action’s mutation definition and the required types in this file. For your login mutation, replace the content of this file with the following and save:

type Mutation {
  login (username: String!, password: String!): LoginResponse
}

type LoginResponse {
  accessToken: String!
}

It is essential that the custom types used in the action are defined beforehand via the set_custom_types metadata API:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type": "set_custom_types",
  "args": {
    "scalars": [],
    "enums": [],
    "input_objects": [],
    "objects": [
      {
        "name": "LoginResponse",
        "fields": [
          {
            "name": "accessToken",
            "type": "String!"
          }
        ]
      }
    ]
  }
}

Once the custom types are defined, we can create an action via the create_action metadata API:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type": "create_action",
  "args": {
    "name": "Login",
    "definition": {
      "kind": "synchronous",
      "type": "mutation",
      "arguments": [
        {
          "name": "username",
          "type": "String!"
        },
        {
          "name": "password",
          "type": "String!"
        }
      ],
      "output_type": "LoginResponse",
      "handler": "https://hasura-actions-demo.glitch.me/login"
    }
  }
}

The above definition means:

This action will be available in your GraphQL schema as a mutation called login.
It accepts two arguments called username and password of type String!.
It returns an output type called LoginResponse.
LoginResponse is a simple object type with a field called accessToken of type String!.

Step 2: Create the action handler¶

A handler is an HTTP webhook where you can perform the custom logic for the action.

In this case, we will just return an access token, but typically you would want to run all the business logic that the action demands. NodeJS/Express code for this handler would look something like:

const handler = (req, resp) => {
  // You can access their arguments input at req.body.input
  const { username, password } = req.body.input;

  // perform your custom business logic
  // check if the username and password are valid and login the user

  // return the response
  return resp.json({
    accessToken: "Ew8jkGCNDGAo7p35RV72e0Lk3RGJoJKB"
  })

};

You can deploy this code somewhere and get the URI. For getting started quickly, we also have this handler ready at https://hasura-actions-demo.glitch.me/login.

Set the handler

Now, set the handler for the action:

Set the value of the handler field to the above endpoint.

Go to metadata/actions.yaml. You must see a handler like http://localhost:3000 or http://host.docker.internal:3000 under the action named login. This is a default value taken from config.yaml. Update the handler to the above endpoint.

The action handler must be set when creating an action via the create_action metadata API.

It can be updated later by using the update_action metadata API.

URL templating

To manage handler endpoints across environments it is possible to template the endpoints using ENV variables.

e.g. https://my-handler-endpoint/addNumbers can be templated to {{ACTION_BASE_ENDPOINT}}/addNumbers where ACTION_BASE_ENDPOINT is an ENV variable whose value is set to https://my-handler-endpoint

Note

If you are running Hasura using Docker, ensure that the Hasura Docker container can reach the handler endpoint. See this page for Docker networking.

Step 3: Finish action creation¶

Finally, to save the action:

Hit Create.

Run hasura metadata apply.

An action will be created when sending a request to the create_action metadata API.

Step 4: Try it out¶

In the Hasura console, head to the GraphiQL tab and try out the new action.

mutation {
  login (username: "jondoe", password: "mysecretpassword") {
    accessToken
  }
}

mutation { login (username: "jondoe", password: "mysecretpassword") { accessToken } }

{ "data": { "login": { "accessToken": "Ew8jkGCNDGAo7p35RV72e0Lk3RGJoJKB" } } }

And that’s it. You have extended your Hasura schema with a new mutation.

Query type action¶

Let’s start with a basic query that accepts a list of numbers and returns their sum. We’ll call this query addNumbers.

Step 1: Define your query and associated types
Step 2: Create the action handler
Step 3: Finish action creation
Step 4: Try it out

Step 1: Define your query and associated types¶

Start with defining the query and the required types. These types will reflect in the GraphQL schema.

Go to the Actions tab on the console and click on Create. This will take you to a page like this:

Define the action as follows in the Action Definition editor.

type Query {
  addNumbers (numbers: [Int]): AddResult
}

In the above action, we called the returning object type to be AddResult. Define it in the New types definition as:

type AddResult {
  sum: Int
}

To create an action, run

hasura actions create addNumbers

This will open up an editor with metadata/actions.graphql. You can enter the action’s query definition and the required types in this file. For your addNumbers query, replace the content of this file with the following and save:

type Query {
  addNumbers (numbers: [Int]): AddResult
}

type AddResult {
  sum: Int
}

It is essential that the custom types used in the action are defined beforehand via the set_custom_types metadata API:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type": "set_custom_types",
  "args": {
    "scalars": [],
    "enums": [],
    "input_objects": [],
    "objects": [
      {
        "name": "AddResult",
        "fields": [
          {
            "name": "sum",
            "type": "Int!"
          }
        ]
      }
    ]
  }
}

Once the custom types are defined, we can create an action via the create_action metadata API:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type":"create_action",
    "args": {
      "name":"addNumbers",
      "definition": {
        "kind":"synchronous",
        "type": "query",
        "arguments":[
          {
            "name":"numbers",
            "type":"[Int]!"
          }
        ],
        "output_type":"AddResult",
        "handler":"https://hasura-actions-demo.glitch.me/addNumbers"
    }
  }
}

The above definition means:

This action will be available in your GraphQL schema as a query called addNumbers
It accepts an argument called numbers which is a list of integers.
It returns an output type called AddResult.
AddResult is a simple object type with a field called sum of type integer.

Step 2: Create the action handler¶

A handler is an HTTP webhook where you can perform the custom logic for the action.

In this case, it is the addition of the numbers. NodeJS/Express code for this handler would look something like:

const handler = (req, resp) => {
  // You can access their arguments input at req.body.input
  const { numbers } = req.body.input;

  // perform your custom business logic
  // return an error or response
  try {
    return resp.json({
      sum: numbers.reduce((s, n) => s + n, 0)
    });
  } catch(e) {
    console.error(e)
    return resp.status(500).json({
      message: 'unexpected'
    })
  }
};

You can deploy this code somewhere and get the URI. For getting started quickly, we also have this handler ready at https://hasura-actions-demo.glitch.me/addNumbers.

Set the handler

Now, set the handler for the action:

Set the value of the handler field to the above endpoint.

Go to metadata/actions.yaml. You must see a handler like http://localhost:3000 or http://host.docker.internal:3000 under the action named addNumbers. This is a default value taken from config.yaml.

Update the handler to the above endpoint.

The action handler must be set when creating an action via the Once the custom types are defined, we can create an action via the create_action metadata API.

It can be updated later by using the update_action metadata API.

URL templating

To manage handler endpoints across environments it is possible to template the endpoints using ENV variables.

e.g. https://my-handler-endpoint/addNumbers can be templated to {{ACTION_BASE_ENDPOINT}}/addNumbers where ACTION_BASE_ENDPOINT is an ENV variable whose value is set to https://my-handler-endpoint

Step 3: Finish action creation¶

Finally, to save the action:

Hit Create.

Run hasura metadata apply.

An action will be created when sending a request to the create_action metadata API.

Step 4: Try it out¶

In the Hasura console, head to the GraphiQL tab and try out the new action.

query {
  addNumbers(numbers: [1, 2, 3, 4]) {
    sum
  }
}

query { addNumbers(numbers: [1, 2, 3, 4]) { sum } }

{ "data": { "addNumbers": { "sum": 10 } } }

And that’s it. You have extended your Hasura schema with a new query.

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