Golang Mutation Example for AWS Lambda

This example trigger updates (executes a mutation) when an event occurs on another table, written in Golang.

Create tables

Table name: note

Columns:

id     Integer auto-increment
note   Text

Primary key: id

Table name: note_revision

Columns:

id         Integer auto-increment
note       Text
note_id    Integer
update_at  Timestamp, default: now()

Primary key: id

Setup AWS Lambda

Create a Lambda function in AWS. This will be our webhook.

1. Sign in to the AWS Management Console and open the AWS Lambda console.
2. Choose "Create a function" under the Get Started section.
3. Select "Author from scratch".
4. Specify the Name for your lambda.
5. Select go 1.x as the Runtime.
6. In Role choose Create new role from template(s)
7. In Role name, enter a name for your role, leave the Policy Templates field blank.
8. Build and upload the code to AWS Lambda:

i. Run the bash script provided

bash build.sh

ii. Upload mutation.zip in the lambda console. 9. In the Designer pane, add an environment variable HGE_ENDPOINT which is the Hasura GraphQL Engine endpoint. 10. Click the save button for the changes to take effect. 11. Create an API with a lambda proxy integration as specified in the AWS Documentation.

Add the trigger in Hasura GraphQL

1. In events tab, add a trigger
2. Select all insert, update, delete operations for the trigger.
3. Paste the API endpoint of your AWS lambda as the webhook.

Test the trigger

Goto Data tab on Hasura console, browse to note table and to the Browse rows tab. Edit an existing note and check if the note_revision entry has been created. Also, checkout the trigger request and response.

Trigger payload (request):

{
    "event": {
        "op": "UPDATE",
        "data": {
            "old": {
                "note": "note1",
                "id": 1
            },
            "new": {
                "note": "note1 updated",
                "id": 1
            }
        }
    },
    "created_at": "2018-10-02T06:38:22.67311Z",
    "id": "f57a1c79-72ba-4c19-8791-37d1b9616bcf",
    "trigger": {
        "name": "note_revision_trigger",
        "id": "5d85cbd1-c134-45ce-810c-7ecd3b4fc1ee"
    },
    "table": {
        "schema": "public",
        "name": "note"
    }
}

Webhook response:

{
    "data": {
        "insert_note_revision": {
            "affected_rows": 1,
            "returning": [
                {
                    "id": 2
                }
            ]
        }
    }
}