How to identify and avoid harmful Magento extensions

This article provides recommendations about how to detect Magento extensions that can negatively affect site and server performance.

General recommendations

While most extensions are not malicious, many developers do not consider the performance impacts their features can have on a site and server. Poorly designed extensions can negatively affect a site's:

  • Stability
  • Performance
  • Security

Therefore, an extension's reputation is very important. Before you download and install an extension, research its online reviews. Does it have consistently negative reviews (or no reviews at all)? If so, you should be cautious.

Some useful search terms for investigating an extension are as follows (replace extension with the name of the extension you are researching):

  • "extension issues"
  • "extension performance"
  • "extension security"

If you are suspicious about a particular extension, there is often another extension with the same functionality that has a better reputation, support, or performance.

The following sections discuss the specific types of extensions that most commonly affect server performance.

Image manipulation extensions

It may seem convenient to be able to crop and resize a batch of images using an extension. However, when you use the web server to do back-office image processing, it can generate a significant load on the processors.

If you use an image manipulation extension, be aware of the original size of the images you are trying to process. If you can, use a local computer to resize images to an appropriate web-safe size before you upload them to the server.

Extensions that do a one-time optimization of images when they are first uploaded generally do not cause a problem.

Related post and related product extensions

A large part of the success of online shops is the ability to offer suggestions to customers based on products that they have viewed or are currently viewing. Extensions generally use one of two methods to provide this functionality (these methods also apply to generating related posts for blogs):

  • The first, and more appropriate, method is to pre-process related products in batches and store a cached copy of related products. The application can then use the cached copy to generate page content faster.
  • The second, and less preferred, method is to offer a new customized list of related products every time a page is loaded.

Try to determine which method an extension uses to generated related content. It can have a significant impact on your site's performance.

Audit logging extensions

It may seem like a good idea to log every single activity that happens on a site in the database. Then if there is a problem, you can find out what happened, right? Unfortunately, excessive logging can generate huge database tables that make a site and its server progressively slower, outweighing any potential diagnostic benefits.

On a more practical note, to track down a problem you must find any relevant data among all of the irrelevant data in the log. Processing this data can be a very processor-intensive task. If you must use audit logging, keep the amount of data logged to a minimum, and make sure that old log data is purged after a few days. This will help prevent database tables from growing to unmanageable sizes.


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