memcache

MongoDB is a NoSQL database that has Drupal integration for various scenarios.

One of these scenarios is using MongoDB as the caching layer for Drupal.

This article describes what is needed to get MongoDB working as a caching layer for your Drupal site. We assume that you have an Ubuntu Server LTS 14.04 or similar Debian derived distro.

Download The Drupal Module

First, download the MongoDB Drupal module. You do not need to enable any MongoDB modules.

We were recently troubleshooting a client site running Drupal 7.x, and main complaint was high memory usage on all the site's pages.

We were able to diagnose and solve two main causes that range from the common to unusual.

This is a Drupal 7 Commerce site with 173 modules, and 3 themes enabled. Apache Solr is used for search, and there is custom code to talk over the network to a non-Drupal backend server.

The site runs on a Debian Squeeze Xen VPS.

For most of the site's pages, the client was seeing high memory usage, as follows:

Problem: high memory usage

By design, the Drupal CAPTCHA module disables page caching for pages it is enabled on.

So if you enable CAPTCHA for user login and/or registration forms, those pages will not be cached. This is often acceptable.

However, if you enable CAPTCHA for comments, and have the comment form visible at the bottom of each node, then a big portion of your site's pages will not be cached in the page cache at all.