withEventLogger

withEventLogger emits one structured SendEvent per send into the supplied event sink. Each event carries the route, message ID, duration, timestamps, and either the result (on success) or a serialized error. Errors are re-thrown after writing so the pipeline still surfaces the failure to the caller.

import { withEventLogger } from '@betternotify/core/middlewares';
import { consoleEventSink } from '@betternotify/core/sinks';

const welcome = rpc
  .email()
  .input(schema)
  .subject(fn)
  .template(adapter)
  .use(withEventLogger({ sink: consoleEventSink() }));

What is a sink?

A sink is a destination for events — an object with a single write(event) method. The middleware calls write once per send and moves on. The sink decides where the event goes: the console, an in-memory array, a database, an HTTP endpoint, a message queue.

This keeps withEventLogger decoupled from any specific observability stack. Better-Notify ships two sinks out of the box:

• consoleEventSink() — logs events to the console. Use during local development.
• inMemoryEventSink() — collects events in an array. Use in tests to assert on what was sent.

For production, implement the EventSink interface to route events to your stack (Datadog, S3, Kafka, an audit database, etc.).

Options

The SendEvent shape

Every send produces exactly one event:

type SendEvent = {
  route: string;
  messageId: string;
  status: 'success' | 'error';
  durationMs: number;
  startedAt: Date;
  endedAt: Date;
  result?: unknown;
  error?: { name: string; message: string; code?: string };
};

Custom sinks

Implement the EventSink interface to send events anywhere:

import type { EventSink } from '@betternotify/core';

const datadogSink: EventSink = {
  write: async (event) => {
    await fetch('https://api.datadoghq.com/api/v2/logs', {
      method: 'POST',
      headers: { 'DD-API-KEY': process.env.DD_API_KEY! },
      body: JSON.stringify(event),
    });
  },
};