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README.md

Serverless ETL demo using Hasura GraphQL Engine Event Triggers and Algolia Search

Live demo at https://serverless-etl.demo.hasura.app/

This application demonstrates an ETL process using event triggers on Hasura GraphQL Engine.

A searchable book library is shown where user can add title and author for new books. When a new book in inserted into the database using GraphQL Mutation, a Google Cloud Function is triggered which updates an Algolia search index. On the search screen, user can search through this index and results are shown using Algolia APIs. As many users add more books, the search index gets bigger.

Instructions

Pre-requisites

  • A Google Cloud account with billing enabled
  • gcloud CLI
  • Algolia account
  • Hasura GraphQL Engine (HGE) installation

Step 1: Create table

Go to HGE console and create the following table:

Table name: book

id           UUID default: gen_random_uuid()
created_at   Timestamp
title        Text
author       Text

Primary key: id

Step 2: Setup an Algolia index

  • Sign-up for Algolia account
  • Go to the Dashboard,
  • Click on Indices tab on the left sidebar
  • Click on New Index button
  • Name it as demo_serverless_etl_app
  • Goto API Keys tab on the sidebar
  • Copy the Application ID (we'll call this APP_ID)
  • Click on All API Keys tab and then click New API Key button
  • Give description as server key
  • Choose the demo_serverless_etl_app index
  • Select Add records under the ACL section
  • Click Generate and copy this API key from the list (we'll call it ADMIN_KEY)
  • Similarly create one more API key called search key for the same index, but ACL as only Search (we'll call this one SEARCH_KEY)

Step 3: Deploy the cloud function

  • Go to cloudfunction directory and deploy the function:
    gcloud beta functions deploy serverless-etl \
           --runtime nodejs8 --trigger-http \
           --set-env-vars="ALGOLIA_APP_ID=<APP_ID>,ALGOLIA_ADMIN_API_KEY=<ADMIN_KEY>"
    Replace APP_ID and ADMIN_KEY with the keys generated in the previous step.
  • Note down the url for triggering the function from the output (call it TRIGGER_URL):
    httpsTrigger:
      url: https://us-central1-hasura-test.cloudfunctions.net/serverless-etl

Step 4: Create an Event Trigger

Go to Events tab in HGE Console and add a new trigger:

Trigger name: book_event
Schema/Table: public/book
Operations:   Insert
Webhook URL:  <TRIGGER_URL>

Use the TRIGGER_URL from previous step.

Step 5: Add configuration variables

Edit index.js and add the following values:

  • HGE_URL, your GraphQL Engine URL (ending with v1alpha1/graphql)
  • APP_ID, the algolia application id
  • SEARCH_KEY, algolia search api key created in Step 2

Step 6: Run the application

Run any HTTP server locally and visit the URL on a browser:

npx http-server

Architecture

Architecture diagram

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