Comet Cache

توسط Cristián Lávaque

If you care about the speed of your site, Comet Cache is one of those plugins that you absolutely MUST have installed 🙂 Comet Cache takes a real-time snapshot (building a cache) of every Page, Post, Category, Link, etc. These snapshots are then stored (cached) intuitively, so they can be referenced later, in order to save all of that processing time that has been dragging your site down and costing you money.

The Comet Cache plugin uses configuration options that you select from the options panel. See: Comet Cache -› Options in your Dashboard. Once a file has been cached, Comet Cache uses advanced techniques that allow it to recognize when it should and should not serve a cached version of the file. By default, Comet Cache does not serve cached pages to users who are logged in, or to users who have left comments recently. Comet Cache also excludes administrative pages, login pages, POST/PUT/DELETE/GET(w/ query string) requests and/or CLI processes.

Features

SIMPLE and well-documented configuration (just enable and you’re all set!).
Options to control the automatic cache clearing behavior for Home and Posts Page, Author Page, Category, Tag, and Custom Term Archives, Custom Post Type Archives, RSS/RDF/ATOM Feeds, and XML Sitemaps.
URI exclusion patterns (now supporting wildcards too).
User-Agent exclusion patterns (now supporting wildcards too).
HTTP referrer exclusion patterns (now supporting wildcards too).
The ability to set an automatic expiration time for cache files.
Client-Side Caching (to allow double-caching in the client-side browser).
Caching for 404 requests to reduce the impact of those requests on the server.
RSS, RDF, and Atom Feed caching.
The ability to cache or ignore URLs that contain query strings (GET Requests).
Apache Optimizations to enable GZIP Compression.
WP-CLI Compatibility.
An Advanced Cache Plugin system for theme and plugin developers.

Pro Features

The ability to cache logged-in users too! (VERY powerful, particularly for membership sites).
A new improved “Clear Cache” button in the admin bar (along with an option to enable/disable this feature).
Options for Automatic and Intelligent Cache Clearing of Posts, Pages, Custom Post Types, Categories, Tags, Links, Themes, Users, and more.
The ability to disable Dashboard notifications related to automatic clearing/purging on change detections.
The ability to clear Markdown-related cache files generated by the s2Clean theme for WordPress (if installed).
The ability to run custom PHP code whenever the cache is cleared.
The ability to Auto-Clear a List of Custom URLs.
Clear Cache User Permissions to give other users permission to clear the cache by specifying a list of Roles and/or Capabilities.
Cache Statistics to help you gain insight into the status of your site cache.
Import/Export functionality for Comet Cache configuration files.
A Dynamic Version Salt (customize the caching engine).
Multisite Host Exclusion Patterns to exclude specific child blogs from being cached in a Multisite Network.
Mobile Mode that supports creating multiple versions of the cache for sites with adaptive designs.
HTML Compressor to automatically combine and compresses CSS/JS/HTML code.
Auto-Cache Engine to pre-cache your site at 15-minute intervals.
Static CDN Filters to serve some and/or ALL static files on your site from a CDN of your choosing, including support for Multiple CDN Host Names, Domain Sharding, and WordPress Multisite Networks.
Domain Sharding / Multiple CDN Hosts to work around concurrency limits and make it possible for browsers to download more resources simultaneously.
Server Load Monitoring to avoid regenerating the cache while the server is very busy by specifying a maximum server load average.
Cache Statistics and Charts to analyze statistics about the page cache, HTML Compressor cache, PHP OPCache, and server health.
Apache Optimizations to enable web server GZIP Compression, Leverage Browser Caching, Enforce Canonical URLs, and more.
An Automatic Updater to update Comet Cache Pro from your WordPress Dashboard.
Compatibility with ManageWP and InfiniteWP.
Rockstar support for all Comet Cache features.

TIP: you can preview Pro features in the free version by clicking the “Preview Pro Features” link at the top of your Comet Cache options.

Further Details

So Why Does WordPress® Need To Be Cached?

To understand how Comet Cache works, first you have to understand what a cached file is, and why it is absolutely necessary for your site and every visitor that comes to it. WordPress® (by its very definition) is a database-driven publishing platform. That means you have all these great tools on the back-end of your site to work with, but it also means that every time a Post/Page/Category is accessed on your site, dozens of connections to the database have to be made, and literally thousands of PHP routines run in harmony behind-the-scenes to make everything jive. The problem is, for every request that a browser sends to your site, all of these routines and connections have to be made (yes, every single time). Geesh, what a waste of processing power, memory, and other system resources. After all, most of the content on your site remains the same for at least a few minutes at a time. If you’ve been using WordPress® for very long, you’ve probably noticed that (on average) your site does not load up as fast as other sites on the web. Now you know why!

The Definition Of A Cached File (from the Wikipedia)

In computer science, a cache (pronounced /kash/) is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch (owing to longer access time) or to compute, compared to the cost of reading the cache. In other words, a cache is a temporary storage area where frequently accessed data can be stored for rapid access. Once the data is stored in the cache, it can be used in the future by accessing the cached copy rather than re-fetching or recomputing the original data.

Prepare To Be Amazed / It’s Time To Speed Things Up

Comet Cache is extremely reliable, because it runs completely in PHP code, and does not hand important decisions off to the mod_rewrite engine or browser cache; also making Comet Cache MUCH easier to setup and configure.

In addition, Comet Cache actually sends a no-cache header (yes, a no-cache header); which allows it to remain in control at all times. It might seem weird that a caching plugin would send a no-cache header :-). Well, no-cache headers are a key component in this plugin, and they will NOT affect performance negatively. On the contrary, this is how the system can accurately serve cache files to public users vs. users who are logged-in, commenters, etc.

Running Comet Cache On A WordPress® Multisite Installation

WordPress® Multisite Networking is a special consideration in WordPress®. If Comet Cache is installed under a Multisite Network installation, it will be enabled for ALL blogs the same way. The centralized config options for Comet Cache, can only be modified by a Super Administrator operating on the main site. Comet Cache has internal processing routines that prevent configuration changes, including menu displays; for anyone other than a Super Administrator operating on the main site.

How To Enable GZIP Compression for Even Greater Speeds

You don’t have to use an .htaccess file to enjoy the performance enhancements provided by this plugin; caching is handled by WordPress®/PHP alone. That being said, if you want to take advantage of GZIP compression (and we do recommend this), then you WILL need an .htaccess file to accomplish that part. This plugin fully supports GZIP compression on its output. However, it does not handle GZIP compression directly. We purposely left GZIP compression out of this plugin, because GZIP compression is something that should really be enabled at the Apache level or inside your php.ini file. GZIP compression can be used for things like JavaScript and CSS files as well, so why bother turning it on for only WordPress-generated pages when you can enable GZIP at the server level and cover all the bases!

If you want to enable GZIP and your site is running on the Apache web server, visit Dashboard -> Comet Cache -> Apache Optimizations -> Enable GZIP Compression?; or to enable GZIP compression manually create an .htaccess file in your WordPress® installation directory (or edit the one that’s already there) and put the following few lines in it. That is all there is to it. GZIP is now enabled!

<IfModule deflate_module>
    <IfModule filter_module>
        AddOutputFilterByType DEFLATE text/plain text/html
        AddOutputFilterByType DEFLATE text/xml application/xml application/xhtml+xml application/xml-dtd
        AddOutputFilterByType DEFLATE application/rdf+xml application/rss+xml application/atom+xml image/svg+xml
        AddOutputFilterByType DEFLATE text/css text/javascript application/javascript application/x-javascript
        AddOutputFilterByType DEFLATE font/otf font/opentype application/font-otf application/x-font-otf
        AddOutputFilterByType DEFLATE font/ttf font/truetype application/font-ttf application/x-font-ttf
    </IfModule>
</IfModule>

If your installation of Apache does not have mod_deflate installed. You can also enable GZIP compression using PHP configuration alone. In your php.ini file, you can simply add the following line anywhere: zlib.output_compression = on

EMERGENCY: If All Else Fails (How-To Remove Comet Cache)

Ordinarily you can just deactivate Comet Cache from the plugins menu in WordPress. However, if you’re having a more serious issue, please follow the instructions here.

Log into your site via FTP; perhaps using FileZilla.
Delete this file: /wp-content/advanced-cache.php
Delete this directory: /wp-content/plugins/comet-cache/
Remove this line from your /wp-config.php file: define('WP_CACHE', TRUE);

Comet Cache is now completely uninstalled and you can start fresh 🙂

Pro Features

Comet Cache Pro Features

The ability to cache logged-in users too! (VERY powerful, particularly for membership sites).
A new improved “Clear Cache” button in the admin bar (along with an option to enable/disable this feature).
Options for Automatic and Intelligent Cache Clearing of Posts, Pages, Custom Post Types, Categories, Tags, Links, Themes, Users, and more.
The ability to disable Dashboard notifications related to automatic clearing/purging on change detections.
The ability to clear Markdown-related cache files generated by the s2Clean theme for WordPress (if installed).
The ability to run custom PHP code whenever the cache is cleared.
The ability to Auto-Clear a List of Custom URLs.
Clear Cache User Permissions to give other users permission to clear the cache by specifying a list of Roles and/or Capabilities.
Cache Statistics to help you gain insight into the status of your site cache.
Import/Export functionality for Comet Cache configuration files.
A Dynamic Version Salt (customize the caching engine).
Multisite Host Exclusion Patterns to exclude specific child blogs from being cached in a Multisite Network.
Mobile Mode that supports creating multiple versions of the cache for sites with adaptive designs.
HTML Compressor to automatically combine and compresses CSS/JS/HTML code.
Auto-Cache Engine to pre-cache your site at 15-minute intervals.
Static CDN Filters to serve some and/or ALL static files on your site from a CDN of your choosing, including support for Multiple CDN Host Names, Domain Sharding, and WordPress Multisite Networks.
Domain Sharding / Multiple CDN Hosts to work around concurrency limits and make it possible for browsers to download more resources simultaneously.
Server Load Monitoring to avoid regenerating the cache while the server is very busy by specifying a maximum server load average.
Cache Statistics and Charts to analyze statistics about the page cache, HTML Compressor cache, PHP OPCache, and server health.
Apache Optimizations to enable web server GZIP Compression, Leverage Browser Caching, Enforce Canonical URLs, and more.
An Automatic Updater to update Comet Cache Pro from your WordPress Dashboard.
Rockstar support for all Comet Cache features.

TIP: you can preview Pro features in the free version by clicking the “Preview Pro Features” link at the top of your Comet Cache options.

Pro Installation

Comet Cache Pro is a wholly contained plugin that does not require Comet Cache Lite to be installed. To install Comet Cache Pro,

Deactivate and delete Comet Cache Lite, if it is currently installed
Download Comet Cache Pro from your account at CometCache.com
From your WordPress Dashboard, go to Dashboard -> Plugins -> Add New and then click on the Upload Plugin button at the top
Select the Comet Cache Pro zip file you downloaded in step 2 and click “Install Now”
After the plugin finishes installing, click the “Activate Plugin” link

Once the plugin is active, you can go to Dashboard -> Comet Cache -> Plugin Options -> Enable/Disable and Enable Comet Cache.

Also, to stay updated with the latest version of Comet Cache Pro, be sure to also configure Dashboard -> Comet Cache -> Plugin Updater.

Software Requirements

In addition to the WordPress Requirements, Comet Cache requires the following minimum versions:

PHP 5.4+
Apache 2.1+

License

Released under the terms of the GNU General Public License.

Credits / Additional Acknowledgments

Software designed for WordPress®.
- GPL License https://codex.wordpress.org/GPL
- WordPress® http://wordpress.org
Some JavaScript extensions require jQuery.
- GPL-Compatible License http://jquery.org/license
- jQuery http://jquery.com/
CSS framework and some JavaScript functionality provided by Bootstrap.
- GPL-Compatible License http://getbootstrap.com/getting-started/#license-faqs
- Bootstrap http://getbootstrap.com/
Icons provided by Font Awesome.
- GPL-Compatible License http://fortawesome.github.io/Font-Awesome/license/
- Font Awesome http://fortawesome.github.io/Font-Awesome/

Quick Tip: WordPress® can only deal with one cache plugin being activated at a time. Please uninstall any existing cache plugins that you’ve tried in the past. In other words, if you’ve installed W3 Total Cache, WP Super Cache, DB Cache Reloaded, or any other caching plugin, uninstall them all before installing Comet Cache. One way to check, is to make sure this file: wp-content/advanced-cache.php and/or wp-content/object-cache.php are NOT present; and if they are, delete these files BEFORE installing Comet Cache. Those files will only be present if you have a caching plugin already installed. If you don’t see them, you’re ready to install Comet Cache :-).

A note for existing ZenCache users: Comet Cache is the successor to ZenCache and will automatically detect any existing ZenCache options and migrate that options over to Comet Cache. For further details, please see the migration FAQ.

Comet Cache is Very Easy to Install

Upload the /comet-cache folder to your /wp-content/plugins/ directory.
Activate the plugin through the Plugins menu in WordPress®.
Navigate to the Comet Cache panel & enable it.

How will I know Comet Cache is Working?

First of all, make sure that you’ve enabled Comet Cache. After you activate the plugin in WordPress, go to the Comet Cache options panel and enable caching (you can’t miss the big yellow checkbox). Then scroll to the bottom and click Save All Changes. All of the other options on that page are already pre-configured for typical usage. Skip them all for now. You can go back through all of these later and fine-tune things the way you like them.

Once Comet Cache has been enabled, you’ll need to log out (and/or clear browser cookies). Cache files are NOT served to visitors who are logged in, and that includes you too 🙂 Cache files are NOT served to recent commenters either. If you’ve commented (or replied to a comment lately); please clear your browser cookies before testing.

To verify that Comet Cache is working, navigate your site like a normal visitor would. Right-click on any page (choose View Source), then scroll to the very bottom of the document. At the bottom, you’ll find comments that show Comet Cache stats and information. You should also notice that page-to-page navigation is lightning fast compared to what you experienced prior to installing Comet Cache.

Running Comet Cache On A WordPress® Multisite Installation

EMERGENCY: If All Else Fails (How-To Remove Comet Cache)

Ordinarily you can just deactivate Comet Cache from the plugins menu in WordPress. However, if you’re having a more serious issue, please follow the instructions here.

Log into your site via FTP; perhaps using FileZilla.
Delete this file: /wp-content/advanced-cache.php
Delete this directory: /wp-content/plugins/comet-cache/
Remove this line from your /wp-config.php file: define('WP_CACHE', TRUE);

Comet Cache is now completely uninstalled and you can start fresh 🙂

سوالات متداول

I already have ZenCache installed; how do I install Comet Cache?

Comet Cache is the successor to ZenCache and will automatically detect any existing ZenCache options and migrate those options over to Comet Cache. For further details, please see the migration FAQ.

How do I know that Comet Cache is working the way it should be?

First of all, make sure that you’ve enabled Comet Cache. After you activate the plugin, go to the Comet Cache options panel and enable it, then scroll to the bottom and click Save All Changes. All of the other options on that page are already pre-configured for typical usage. Skip them all for now. You can go back through all of them later and fine-tune things the way you like them.

What is the downside to running Comet Cache?

There is NOT one! Comet Cache is a MUST HAVE for every WordPress® powered site. In fact, we really can’t think of any site running WordPress® that would want to be without it. To put it another way, the WordPress® software itself comes with a built in action reference for an advanced-cache.php file, because WordPress® developers realize the importance of such as plugin. The /wp-content/advanced-cache.php file is named as such, because the WordPress® developers expect it to be there when caching is enabled by a plugin. If you don’t have the /wp-content/advanced-cache.php file yet, it is because you have not enabled Comet Cache from the options panel yet.

So why does WordPress® need to be cached?

Where & why are the cache files stored on my server?

The cache files are stored in a special directory: /wp-content/cache/comet-cache. This directory needs to remain writable, just like the /wp-content/uploads directory on many WordPress® installations. The /comet-cache/cache directory is where cache files reside. These files are stored using an intutive directory structure that named based on the request URL (HTTPS/HTTP_HOST/REQUEST_URI). See also: Dashboard -› Comet Cache -› Cache Directory/Expiration Time for further details.

Whenever a request comes in from someone on the web, Comet Cache checks to see if it can serve a cached file; e.g. it looks at the HTTPS/HTTP_HOST/REQUEST_URI environent variables, then it checks the /comet-cache/cache directory. If a cache file has been built already, and it matches an existing HTTPS.HTTP_HOST.REQUEST_URI combination; and it is not too old (see: Dashboard -› Comet Cache -› Cache Directory/Expiration Time), then it will serve that file instead of asking WordPress® to regenerate it. This adds tremendous speed to your site and reduces server load.

What happens if a user logs in? Are cache files used then?

By default, Comet Cache does NOT serve cached pages to users who are logged in, or to users who have left comments recently. Comet Cache also excludes administrative pages, login pages, POST/PUT/DELETE/GET(w/ query string) requests and/or CLI processes. That being said, the Pro version of Comet Cache DOES make it possible to cache pages even when users ARE logged-in; adding even more speed! This is particularly helpful on membership sites; e.g. sites that run plugins like s2Member™ for instance.

Will comments and other dynamic parts of my blog update immediately?

It depends on your configuration of Comet Cache. There is an automatic expiration system (the garbage collector), which runs through WordPress® behind-the-scene, according to your Expiration setting (see: Dashboard -› Comet Cache -› Cache Directory/Expiration Time). There is also a built-in expiration time on existing files that is checked before any cache file is served up, which also uses your Expiration setting. In addition; whenever you update a Post or a Page, Comet Cache can automatically prune that particular file from the cache so it instantly becomes fresh again. Otherwise, your visitors would need to wait for the previous cached version to expire.

How do I enable GZIP compression? Is GZIP supported?

There is no need to use an .htaccess file with this plugin; caching is handled by WordPress®/PHP alone. That being said, if you also want to take advantage of GZIP compression (and we do recommend this), then you WILL need an .htaccess file to accomplish that part. This plugin fully supports GZIP compression on its output. However, it does not handle GZIP compression directly. We purposely left GZIP compression out of this plugin, because GZIP compression is something that should really be enabled at the Apache level or inside your php.ini file. GZIP compression can be used for things like JavaScript and CSS files as well, so why bother turning it on for only WordPress-generated pages when you can enable GZIP at the server level and cover all the bases!

<IfModule deflate_module>
    <IfModule filter_module>
        AddOutputFilterByType DEFLATE text/plain text/html
        AddOutputFilterByType DEFLATE text/xml application/xml application/xhtml+xml application/xml-dtd
        AddOutputFilterByType DEFLATE application/rdf+xml application/rss+xml application/atom+xml image/svg+xml
        AddOutputFilterByType DEFLATE text/css text/javascript application/javascript application/x-javascript
        AddOutputFilterByType DEFLATE font/otf font/opentype application/font-otf application/x-font-otf
        AddOutputFilterByType DEFLATE font/ttf font/truetype application/font-ttf application/x-font-ttf
    </IfModule>
</IfModule>

If your installation of Apache does not have mod_deflate installed. You can also enable gzip compression using PHP configuration alone. In your php.ini file, you can simply add the following line anywhere: zlib.output_compression = on

I’m a plugin developer. How can I prevent certain files from being cached?

<?php
define(‘COMET_CACHE_ALLOWED’, FALSE); // The easiest way.
// or $_SERVER[‘COMET_CACHE_ALLOWED’] = FALSE; // Also very easy.
// or define(‘DONOTCACHEPAGE’, TRUE); // For compatibility with other cache plugins.

When your script finishes execution, Comet Cache will know that it should NOT cache that particular page. It does not matter where or when you define this Constant; e.g. define('COMET_CACHE_ALLOWED', FALSE); because Comet Cache is the last thing to run during execution. So as long as you define this Constant at some point in your routines, everything will be fine.

Comet Cache also provides support for define('DONOTCACHEPAGE', TRUE), which is used by the WP Super Cache plugin as well. Another option is: $_SERVER['COMET_CACHE_ALLOWED'] = FALSE. The $_SERVER array method is useful if you need to disable caching at the Apache level using mod_rewrite. The $_SERVER array is filled with all environment variables, so if you use mod_rewrite to set the COMET_CACHE_ALLOWED environment variable, that will end up in $_SERVER['COMET_CACHE_ALLOWED']. All of these methods have the same end result, so it’s up to you which one you’d like to use.

What should my expiration setting be?

If you don’t update your site much, you could set this to 6 months; optimizing everything even further. The longer the cache expiration time is, the greater your performance gain. Alternatively, the shorter the expiration time, the fresher everything will remain on your site. A default value of 7 days (recommended expiration time), is a good conservative middle-ground.

Keep in mind that your expiration setting is only one part of the big picture. Comet Cache will also purge the cache automatically as changes are made to the site (i.e. you edit a post, someone comments on a post, you change your theme, you add a new navigation menu item, etc., etc.). Thus, your expiration time is really just a fallback; e.g. the maximum amount of time that a cache file could ever possibly live.

That being said, you could set this to just 60 seconds and you would still see huge differences in speed and performance. If you’re just starting out with Comet Cache (perhaps a bit nervous about old cache files being served to your visitors); you could set this to something like 30 minutes and experiment with it while you build confidence in Comet Cache. It’s not necessary, but many site owners have reported this makes them feel like they’re more-in-control when the cache has a short expiration time. All-in-all, it’s a matter of preference 🙂

EMERGENCY: If all else fails, how can I remove Comet Cache?

Ordinarily you can just deactivate Comet Cache from the plugins menu in WordPress. However, if you’re having a more serious issue, please follow the instructions here.

Log into your site via FTP; perhaps using FileZilla.
Delete this file: /wp-content/advanced-cache.php
Delete this directory: /wp-content/plugins/comet-cache/
Remove this line from your /wp-config.php file: define('WP_CACHE', TRUE);

Comet Cache is now completely uninstalled and you can start fresh 🙂