Custom business logic with Hasura

@aleksandrasays

whoami?

Team Lead at Hasura

Twitter: @aleksandrasays

GitHub: @beerose

Blog: aleksandra.codes

Agenda

@aleksandrasays

What is Hasura?
Remote Schemas
Event Triggers
Hasura Actions

Introduction to Hasura

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What is Hasura?

Instant GraphQL for all your data

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Realtime GraphQL Engine

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GraphQL Queries Compiler

users {
  name
  posts {
    title
    content
    tags {
      name
    }
  }
}

SELECT 
  users.name
  posts.title
  posts.content
  tags.name
FROM 
  users, posts, tags
WHERE
  users.id = posts.author_id,
  posts.id = tags.post_id

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Multiple databases

App

Postgres
Yugabyte
Timescale
MS SQL Server
Big Query

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Hasura Cloud

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Authorization

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Rest Endpoints

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Business logic with Hasura

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App

Remote Schemas

Unified GraphQL API

GraphQL Service

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Data Triggers

APIs

Background jobs

GraphQL mutations

Event queue

Microservices

Serverless functions

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Cron Triggers

Event queue

Microservices

Serverless functions

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One-off Scheduled Triggers

Event queue

Microservices

Serverless functions

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Actions

App

</>

GraphQL 
query / mutation

POST endpoint

Actions

How does it work?

mutation createUser(user: {...}) {
  ...
}

{
  "input": {
    "user": {...}
  },
  "session_variables": {...}
}

1. GraphQL operation → Event payload

How does it work?

Async Mode: Event captured → Persisted → Event delivered

2. Delivering event to the webhook


{ ... }

Event store

</>

How does it work?

2. Delivering event to the webhook

Sync Mode: Event captured → Event delivered


{ ... }

</>

How does it work?

3. Receiving event response

Async Mode: event is put back in the event store

Event store


{ ... }

Event store

</>

</>

How does it work?

3. Receiving event response

Sync mode: Hasura keeps the request open till receiving a response from the handler


{ ... }

</>

</>

How does it work?

4. Getting results of the event handler

Async mode: Event response → GraphQL subscription

subscription {
  createUserResult(actionId: "") {
    userId
    
    events {
      name
      date
    }
  }
}

Event store

Postgres DB

How does it work?

4. Getting results of the event handler

Sync mode: Event response → GraphQL operation

mutation {
  createUser(user: {...}) {
    userId
    
    events {
      name
      date
    }
  }
}

</>

@aleksandrasays

Takeaways

https://hasura.io

https://github.com/hasura/graphql-engine

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