RabbitMQ

Publish decoded events to a RabbitMQ exchange — direct, topic, or fanout — using amqplib.

Installation

pnpm add amqplib
pnpm add -D @types/amqplib

Configure the client

src/clients/rabbitmq.ts

import amqp from "amqplib";

let chanPromise: Promise<amqp.Channel> | undefined;

export const getChannel = () =>
  (chanPromise ??= (async () => {
    const conn = await amqp.connect(process.env.RABBITMQ_URL!);
    const ch = await conn.createChannel();
    await ch.assertExchange("transfer", "direct", { durable: true });
    return ch;
  })());

Define the effect

Exchange and routing key are static config — bake them in. input is just the per-event values.

src/effects/rabbitmq.ts

import { createEffect, S } from "envio";
import { getChannel } from "../clients/rabbitmq";

const EXCHANGE = "transfer";
const ROUTING_KEY = "my-routing-key";

export const publishTransfer = createEffect(
  {
    name: "publishTransfer",
    input: {
      from: S.string,
      to: S.string,
      value: S.bigint,
      txHash: S.string,
    },
    rateLimit: { calls: 200, per: "second" },
    mode: "unorderedAfterCommit",
  },
  async ({ input }) => {
    const ch = await getChannel();
    const body = JSON.stringify({ ...input, value: input.value.toString() });
    ch.publish(EXCHANGE, ROUTING_KEY, Buffer.from(body), {
      contentType: "application/json",
      persistent: true,
    });
  }
);

Call it from a handler

The rindexer config…

streams:
  rabbitmq:
    exchanges:
      - exchange: transfer
        exchange_type: direct
        routing_key: my-routing-key
        events:
          - event_name: Transfer
            conditions:
              - "value": ">=2000000000000000000 && value <=4000000000000000000"
              - "from": "0x0338ce5020c447f7e668dc2ef778025ce3982662"

…becomes:

src/handlers/RocketPoolETH.ts

import { indexer } from "envio";
import { publishTransfer } from "../effects/rabbitmq";

const WHALE = "0x0338ce5020c447f7e668dc2ef778025ce3982662";
const MIN = 2_000_000_000_000_000_000n;
const MAX = 4_000_000_000_000_000_000n;

indexer.onEvent(
  { contract: "RocketPoolETH", event: "Transfer" },
  async ({ event, context }) => {
    const { from, to, value } = event.params;

    if (from.toLowerCase() === WHALE && value >= MIN && value <= MAX) {
      context.effect(publishTransfer, {
        from,
        to,
        value,
        txHash: event.transaction.hash,
      });
    }
  },
);

Pick orderedAfterCommit if your consumer needs strict per-batch ordering. For fanout exchanges, leave routingKey as an empty string. If your consumer is idempotent and you want lower latency, switch the effect to mode: "unordered" (or "ordered") to publish inline before the DB commit.