AWS Appsync Invoke mutate from Lambda?

Question

I have a client app subscribed to Appysync events. The data source is a Lambda function to RDS. Is it possible to Invoke the mutate from Lambda function which gets triggered on RDS update?

Answer 1

If I understand you correctly you would like to invoke a mutation from a lambda function that is triggered via an update in RDS with the intention of notifying subscribed clients of the change in RDS. If this is incorrect stop me now.

I'll assume you are doing something like described here to trigger the lambda when something changes in RDS (https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/AuroraMySQL.Integrating.Lambda.html).

To finish the workflow what I recommend doing is creating a Local resolver (a resolver that points to a 'None' data source) and having your lambda function invoke that mutation resolver with the data you want pushed to client apps whenever something changes in RDS. Your clients would then subscribe to the mutation field with the local resolver (instead of the resolver to the RDS lambda) using the @aws_subscribe directive. This way your connected clients will be informed of any RDS changes that might be made via AppSync or might be made via a direct connection to your SQL instance.

Hope this helps.

Answer 2

I found a question, very similar to yours, answered in this post:

How to send GraphQL mutation from one server to another?

Resuming, you can simply dispatch a HTTP request to your Graphql Server (like an API Gateway) and include the Graphql query (can be a mutation too) as a payload. It seems works for me :)

EDIT:

This lambda below I used when trigged by insert on a DynamoDB table:

import json
import requests

GRAPHQL_URL = 'https://XXXXXXXXXXXXXXXXX.appsync-api.ap-southeast-2.amazonaws.com/graphql'

GRAPHQL_API_KEY = "************************************" (secret)

HEADERS = {
    "X-Api-Key":GRAPHQL_API_KEY,
}

def lambda_handler(event, context):

    for record in event['Records']:
        if record['eventName'] == 'INSERT':
            item = record['dynamodb']
            res = {}
            data = {"operationName":None,"variables":{"id":item['NewImage']['id']['S'],"name":item['NewImage']['name']['S'],"when":item['NewImage']['when']['S'],"where":item['NewImage']['where']['S'],"description":item['NewImage']['description']['S']},"query":"mutation ($id: ID!, $name: String!, $when: String!, $where: String!, $description: String!) {\n  eventCreated(id: $id, name: $name, when: $when, where: $where, description: $description) {\n    id\n    name\n    where\n    when\n    description\n    comments {\n      items {\n        commentId\n        __typename\n      }\n      __typename\n    }\n    __typename\n  }\n}\n"}

            try:
                res = requests.post(
                    GRAPHQL_URL,
                    headers=HEADERS,
                    data=json.dumps(data)
                )

            except Exception as e:
                print('error: ', e)
            print('Graphql request response: ', res)
    return 'Successfully processed {} records.'.format(len(event['Records']))