buffered-reconnector's Introduction

buffered-reconnector

Attempts to solve a common problem: transparently reconnecting to a remote resource when it unexpectedly disconnects, and buffering calls while attempting to reconnect. Buffer limits and timeouts are supported.

Example reconnecting to RabbitMQ automatically with amqplib

import Reconnector from "buffered-reconnector";
import amqp from "amqplib";

const rc = new Reconnector(function (bridge) {
  // this function is called the "initializer"
  const connP = amqp.connect();
  const chanP = connP.then(conn => conn.createChannel());

  chanP.then(chan => {
    chan.on("error", () => bridge.hasDisconnected());
    bridge.hasConnected();
  });

  bridge.onClose(() => connP.then(conn => conn.close()));

  return chanP;
});

// needs ES6 proxy
const prox = rc.createProxy();

// you can call this method immediately (i.e. while establishing a connection)
prox.sendToQueue("my_queue", new Buffer("hello!"))
  .then(() => rc.close());

// or, without proxies, there's this sort of balky API
rc.call("sendToQueue", ["my_queue", new Buffer("hello")])
   .then(() => rc.close());

// now the process can exit cleanly

A couple things to note about properly implementing the initializer, for any underlying client.

It is required to call bridge.onClose in the initializer function. This determines how to close the underlying connection cleanly.
The initializer should call bridge.hasConnected to signal that the connection has been established.
The initializer should call bridge.hasDisconnected to signal that the connection has been interrupted.
createProxy() and call() forward method calls to the object/promise returned from the initializer.

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