Trigger Inngest events from database changes

In your functions.ts file (typically located in src/inngest/functions.ts), create a new function:

  import { inngest } from "./client";

  export const sendWelcomeEmail = inngest.createFunction(
      { id: "send-welcome-email" },
      { event: "webhook/users.insert" },
      async ({ event }) => {
          const user = event.data;
          //function to send welcome email
          return { event, body: `Welcome email sent to ${user.email} with subject "Hi ${user.name}"` };
      },
  );

This function takes the webhook/users.insert event as input, extracts the user data, and sends a welcome email to the user.

The Inngest.serve() handler registers your function with Inngest so it can invoke the function.

In your route.ts file (typically located in src/app/api/inngest/route.ts) register the sendWelcomeEmail function:

import { serve } from "inngest/next";
import { inngest } from "../../../inngest/client";
import { sendWelcomeEmail } from "../../../inngest/functions";

export const { GET, POST, PUT } = serve({
  client: inngest,
  functions: [sendWelcomeEmail],
});

Test the sendWelcomeEmail function by trigger a test eveng in the Inngest development server:

1. Run your Next.js project and Start the Inngest development server:

   npm run dev
   # in a new terminal, start the inngest development server
   npx inngest-cli@latest dev
   

2. Open the Inngest dashboard in your browser and navigate to the Functions tab.
3. You should see the send-welcome-email function. Click the Invoke button and enter the following event payload:

   {
       "data": {
           "name": "John Doe",
           "email": "john.doe@example.com"
       }
   }
   

4. Click the Invoke Function button and then navigate to the Runs tab. You should see the run you just triggered:

In the Inngest Cloud Dashboard, navigate to the Webhooks tab and click the Create Webhook button.

Sequin will send a payload to your webhook containing the database change:

{
  "record": {
    "id": 1,
    "name": "John Doe",
    "email": "john.doe@example.com"
  },
  "changes": null,
  "action": "insert",
  "metadata": {
    "table_schema": "public",
    "table_name": "users",
    "commit_timestamp": "2024-02-20T14:30:00Z",
    "consumer": {
      "id": "e2f9a3b1-7c6d-4b5a-9f8e-1d2c3b4a5e6f",
      "name": "new_user_consumer"
    }
  }
}

You need to transform this payload into an Inngest event that triggers the sendWelcomeEmail function. To do so, use a Transfrom to extract the the event name and data from the Sequin payload:

function transform(evt, headers = {}, queryParams = {}) {
  return {
    // Rename this webhook to give the events a unique name,
    // or use a field from the incoming event as the event name.
    name: `webhook/${evt.metadata.table_name}.${evt.action}`,
    data: evt.record,
  };
};

This will create an Inngest event with the name webhook/users.insert and the data from the Sequin record field:

1. Login to your Sequin account and click the Add New Database button.
2. Enter the connection details for your Postgres database.
3. Follow the instructions to create a publication and a replication slot by running two SQL commands in your database:

create publication sequin_pub for all tables;
select pg_create_logical_replication_slot('sequin_slot', 'pgoutput');

4. Name your database and click the Connect Database button.

Sequin will connect to your database and ensure that it’s configured properly.

With your database connected, create a push consumer that will send events to Inngest:

1. Navigate to the Consumers tab and click the Create Consumer button.
2. Select your users table (i.e public.users).
3. Select to process changes and click Continue.
4. Configure which kinds of changes you want to capture and apply filters (for instance, ignore internal emails). Since you just want to email all new users, you’ll capture just the insert changes and apply no additional filters:

5. On the next screen, select Push to have Sequin send the events to your webhook URL. Click Continue.
6. Now, give your consumer a name (i.e. new_user_consumer) and in the HTTP Endpoint section enter the webhook URL you created in Inngest as the Base URL. You don’t need any headers or a path:

7. Click the Create Consumer button. Sequin will varify your database is set up properly and may give you another SQL command to run to ensure every new user is captured.

Insert a new user into your database:

insert into users (name, email) values ('John Doe', 'john.doe@example.com');

In the Sequin console, navigate to the Trace tab and confirm that Sequin delivered the event to Inngest:

In the Inngest Cloud dashboard, navigate to the Events tab, select the webhook/users.insert event, and open the Logs tab. You should see the event you just created:

Now, click the Send to Dev Server button to forward the event to your local Inngest development server.

Finally, in your local Inngest development server, navigate to the Runs tab and confirm that the event was received and your send-welcome-email function was invoked: