2.2.1 • Public • Published

    ewd-qoper8-cache: Integrates ewd-qoper8 worker modules with InterSystems Cache database

    Rob Tweed rtweed@mgateway.com
    24 February 2016, M/Gateway Developments Ltd http://www.mgateway.com

    Twitter: @rtweed

    Google Group for discussions, support, advice etc: http://groups.google.co.uk/group/enterprise-web-developer-community


    This module may be used to simplifiy the integration of the InterSystems Cache database with ewd-qoper8 worker process modules. It additionally loads the ewd-document-store module to provide a very powerful and natural JavaScript interface to the underlying Global Storage database engine within Cache.


       npm install ewd-qoper8-cache

    Using ewd-qoper8-cache

    This module should be used with the start event handler of your ewd-qoper8 worker module, eg:

    this.on('start', function(isFirst) {
      var connectCacheTo = require('ewd-qoper8-cache');

    This will open a connection to a Cache database using the following default parameters:

      path: '/opt/cache/mgr',
      username: '_SYSTEM',
      password: 'SYS',
      namespace: 'USER',
      charset: 'UTF-8'

    If you want to modify any of these parameters, simply specify any differences and pass the params object as the second argument, eg to change just the namespace:

    this.on('start', function(isFirst) {
      var connectCacheTo = require('ewd-qoper8-cache');
      var params = {
        namespace: 'GOLD'
      connectCacheTo(this, params);

    ewd-qoper8-cache will load and initialise the ewd-document-store module, creating a DocumentStore object within your worker.

    ewd-qoper8-cache takes responsibility for handling the 'stop' event, but provides you with 3 new events that you may handle:

    • dbOpened: fires after the connection to Cache is opened within a worker process
    • dbClosed: fires after the connection to Cache is closed within a worker process. The worker exits immediately after this event
    • DocumentStoreStarted: fires after the DocumentStore object has been instantiated. This is a good place to handle DocumentStore events, for example to maintain Document indices

    The dbOpened event provides you with a single status object argument, allowing you to determine the success (or not) of opening the connection to Cache, so you could add the following handler in your worker module, for example:

    this.on('dbOpened', function(status) {
      console.log('Cache was opened by worker ' + process.pid + ': status = ' + JSON.stringify(status));

    The dbClosed and DocumentStoreStarted events provide no arguments.


    See in the /examples directory.

    cache-express,js is an example Express & ewd-qoper8 master process scripts. gtm-module1.js is the associated worker module which connects to and uses Cache as the database providing the Document Store.

    Use these as a starting point for your own system.


    Copyright (c) 2016 M/Gateway Developments Ltd,
    Reigate, Surrey UK.
    All rights reserved.

    Email: rtweed@mgateway.com

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at


    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and
    limitations under the License.




    npm i ewd-qoper8-cache

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