Drupal 6 Performance Optimization Using Throttle and Devel Module

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Enabling and configuring the Throttle module

Drupal allows you to control when your modules and blocks get enabled and shown to your site visitors. This helps you to prevent bottlenecks in your server’s web traffic and to optimize your server load to prevent any congestion that it might experience with its bandwidth and traffic. Throttling blocks and modules becomes increasingly important on larger scale websites where you have many blocks and modules active. You may have a site that contains a large number of blocks, for example, that have been built with the Views module. You can throttle these blocks, so they only get enabled when the site visitor calls a page that is supposed to show that block. The throttle module allows you to configure it, so it automatically gets enabled when the usage of your site goes above a certain threshold. For example, this can be the number of anonymous users visiting your site. When a certain amount of visitors are on your site, you can have Drupal enable throttling.

Using the Throttle module is essential on shared servers where you may not have all of the resources on the server made available to you at any given time or on a server that gives you limited CPU resources and bandwidth. You may not need to use Throttle on higher performance-dedicated servers because they will most likely be providing you with good performance. But on shared servers it does become important to use Throttle.

If you did not enable the Throttle module after we upgraded our site to Drupal 6.13, we need to enable it first. Once enabled, we can then configure the module. Follow these steps:

Under your Core-optional module list, check the box next to Throttle and then save your module configuration.

Drupal 6 Performance Optimization Using Throttle and Devel Module

There are two methods of accessing the Throttle module configuration. You can visit the main Throttle configuration page to set auto throttling settings for your site. Also, you can enable throttling for each module and block on your site. We’ll look at both methods now. Note that your modules admin page explains how to access and enable both types of throttling (module and auto) at the top of the page in its introductory help text. You will only see your module throttle checkboxes available if you have enabled the Throttle module first.

Configuring the Throttle module for auto throttling features

Go to Site configuration | Throttle to load your Throttle module settings form or click on the throttle configuration page link through your main modules admin page.

The Throttle configuration page explains what the Throttle module does and gives you a link to more information through the more help link. If you click on that link and have the Advanced Help module active, you will launch a detailed Throttle module help and explanation page.

On this page you can configure three throttle elements that fall under the default Throttle module congestion control feature:

  • Auto-throttle on anonymous users
  • Auto-throttle on authenticated users
  • Auto-throttle probability limiter

Auto-throttle on anonymous users allows you to set a threshold for enabling your congestion control throttle dependent on anonymous user activity. So, for example, you will want to choose a threshold number of anonymous users to enter into this field. When this number of anonymous users is reached, the auto-throttle feature will be enabled. If you want the auto-throttle to be enabled after 250 anonymous users are on your site at the same time, you can type 250 into this field. Set this field to 0 if you do not want to use the auto-throttle feature.

Drupal also tells you here that you can determine how many users are on your site at any given time by enabling the Who’s Online block—this will show you all of the anonymous users who are browsing your site and authenticated users who are logged into your site.

The Auto-throttle on authenticated users works using the same method. Add the threshold number of authenticated users that you want logged into your site before the point your throttle gets enabled. We’ll set this to 50 authenticated users.

Drupal 6 Performance Optimization Using Throttle and Devel Module

The Auto-throttle probability limiter helps to reduce the overhead of the auto-throttle module. It’s a built-in performance check just for this Throttle module. You can set a pe rcentage of page views for your site. For example, if you set the page view percentage to 10%, then the module will only perform extra database queries to update the Throttle module status once for every 10 page views. Drupal tells you that the busier your website, the lower you want to set this value. Leave it set to the default of 10%. Save your auto-throttle configuration.

Throttling your modules

You can also throttle each of your core and contributed modules as long as they have a Throttle checkbox next to their line item on the modules admin page. Load your modules admin page and look for the Throttle checkboxes. This allows you to tell Drupal to throttle a specific module during high traffic periods on your site. This means that when your site reaches a high traffic threshold (based on the auto throttling settings you determined above) your site will temporarily disable the module in question. This will throttle the module until your site returns to a stable status.

You do need to be careful here. You should throttle those modules that are of lesser importance when your site reaches its threshold of user activity. When you throttle, you are temporarily disabling the module, so it will also temporarily disable that module’s functionality during high server loads. So, you may want to disable some modules, such as Views, but leave your CCK module enabled so that your users can still see the content that is being filtered into the View. We’ll go ahead and throttle the following modules:

  • Administration menu (because this module is only being used by our logged in admins)
  • Chaos tool suite (all submodules here)
  • Comment
  • Contact
  • Database logging
  • Help
  • PHP filter
  • Search
  • Statistics
  • Advanced Help
  • FCKEditor
  • IMCE
  • Lightbox2
  • Poormanscron

You can select more modules to throttle based on your preferences and the usage of your site. Use the above as an example and model to follow. Check the throttle boxes and save your configuration. During the next high server load period, these modules will be disabled temporarily to increase the performance of your site during its high server load period.

Drupal 6 Performance Optimization Using Throttle and Devel Module

Throttling blocks

You can also throttle your blocks. To do this, go to the Blocks admin page here: Administer | Site building | Blocks. You’ll notice that there is a new checkbox selection for Throttle. You can choose which blocks to throttle by checking the Throttle checkbox next to each of your enabled blocks. We’ll go ahead and throttle all of our blocks except for the User login, as we still want to allow users to login to the site during high traffic periods. The throttle functionality works the same here as it does with modules. These blocks will be temporarily disabled during high site traffic.

Drupal 6 Performance Optimization Using Throttle and Devel Module

Once you check your throttle boxes, save your blocks configuration. The next time you have high site traffic, these blocks will be temporarily disabled.

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