mongo-oplog/lib/filter.js

Watch mongodb oplog in a simple way

'use strict';

const Emitter = require('eventemitter3');
const dbg = require('debug');

const events = {
  i: 'insert',
  u: 'update',
  d: 'delete'
};

function regex(pattern) {
  pattern = pattern || '*';
  pattern = pattern.replace(/[*]/g, '(.*?)');
  return new RegExp(`^${pattern}$`, 'i');
}

module.exports = (ns, oplog) => {
  const debug = dbg('mongo-oplog:filter');
  const filter = new Emitter();
  const re = regex(ns);

  debug('initializing filter with re %s', ns);

  function onop(doc) {
    if (!re.test(doc.ns) || filter.ignore) return;
    debug('incoming data %j', doc);
    filter.emit('op', doc);
    if (events[doc.op]) {
      filter.emit(events[doc.op], doc);
    }
  }

  function destroy() {
    debug('removing filter bindings');
    oplog.removeListener('op', onop);
    filter.removeAllListeners();
  }

  oplog.on('op', onop);

  return Object.assign(filter, { destroy });
};

module.exports.regex = regex;