Add how-to guide: Figure out why WordPress is slow

bin/handbook-manifest.json

@@ -341,6 +341,12 @@
         "markdown_source": "https:\/\/github.com\/wp-cli\/handbook\/blob\/main\/how-to\/how-to-start-webserver.md",
         "parent": "how-to"
     },
+    "figure-out-why-wordpress-is-slow": {
+        "title": "Figure out why WordPress is slow",
+        "slug": "figure-out-why-wordpress-is-slow",
+        "markdown_source": "https:\/\/github.com\/wp-cli\/handbook\/blob\/main\/how-to\/figure-out-why-wordpress-is-slow.md",
+        "parent": "how-to"
+    },
     "identify-plugin-theme-conflict": {
         "title": "Identify a Plugin or Theme Conflict",
         "slug": "identify-plugin-theme-conflict",

how-to.md

@@ -12,3 +12,5 @@ tasks.
 - [How-to start the webserver](https://make.wordpress.org/cli/handbook/)
 
 - [How to create a custom plugin](https://make.wordpress.org/cli/handbook/how-to-create-custom-plugins)
+
+- [Figure out why WordPress is slow](https://make.wordpress.org/cli/handbook/figure-out-why-wordpress-is-slow)

how-to/figure-out-why-wordpress-is-slow.md

@@ -0,0 +1,89 @@
+# Figure out why WordPress is slow
+
+`wp profile` is a WP-CLI command to help you quickly identify what's slow with WordPress. It's designed to work alongside Xdebug and New Relic because it's easy to deploy to any server that has WP-CLI. With `wp profile`, you gain quick visibility into key performance metrics (execution time, query count, cache hit/miss ratio, etc.) to guide further debugging.
+
+## Installation
+
+First, install the `wp profile` package if you haven't already:
+
+```
+$ wp package install wp-cli/profile-command
+```
+
+### Step 1 - Profile the WordPress load process
+
+Dealing with a slow WordPress install you've never worked with before? Run `wp profile stage` to see metrics for each stage of the WordPress load process. Include the `--url=<url>` argument to mock the request as a specific URL.
+
+```
+$ wp profile stage --url=runcommand.io
++------------+---------+------------+-------------+-------------+------------+--------------+-----------+------------+--------------+---------------+
+| stage      | time    | query_time | query_count | cache_ratio | cache_hits | cache_misses | hook_time | hook_count | request_time | request_count |
++------------+---------+------------+-------------+-------------+------------+--------------+-----------+------------+--------------+---------------+
+| bootstrap  | 0.7597s | 0.0052s    | 14          | 93.21%      | 357        | 26           | 0.3328s   | 2717       | 0s           | 0             |
+| main_query | 0.0131s | 0.0004s    | 3           | 94.29%      | 33         | 2            | 0.0065s   | 78         | 0s           | 0             |
+| template   | 0.7041s | 0.0192s    | 147         | 92.16%      | 2350       | 200          | 0.6982s   | 6130       | 0s           | 0             |
++------------+---------+------------+-------------+-------------+------------+--------------+-----------+------------+--------------+---------------+
+| total (3)  | 1.477s  | 0.0248s    | 164         | 93.22%      | 2740       | 228          | 1.0375s   | 8925       | 0s           | 0             |
++------------+---------+------------+-------------+-------------+------------+--------------+-----------+------------+--------------+---------------+
+```
+
+When WordPress handles a request from a browser, it's essentially executing as one long PHP script. `wp profile stage` breaks the script into three stages:
+
+* **bootstrap** is where WordPress is setting itself up, loading plugins and the main theme, and firing the `init` hook.
+* **main_query** is how WordPress transforms the request (e.g. /2016/10/21/moms-birthday/) into the primary WP_Query.
+* **template** is where WordPress determines which theme template to render based on the main query, and renders it.
+
+### Step 2 - Dive into a specific stage
+
+In the example from above, bootstrap seems a bit slow, so let's dive into it further. Run `wp profile stage bootstrap` to dive into higher fidelity mode of a given stage. Use the `--spotlight` flag to filter out the zero-ish results.
+
+```
+$ wp profile stage bootstrap --url=runcommand.io --spotlight
++--------------------------+----------------+---------+------------+-------------+-------------+------------+--------------+--------------+---------------+
+| hook                     | callback_count | time    | query_time | query_count | cache_ratio | cache_hits | cache_misses | request_time | request_count |
++--------------------------+----------------+---------+------------+-------------+-------------+------------+--------------+--------------+---------------+
+| muplugins_loaded:before  |                | 0.1644s | 0.0017s    | 1           | 40%         | 2          | 3            | 0s           | 0             |
+| muplugins_loaded         | 2              | 0.0005s | 0s         | 0           | 50%         | 1          | 1            | 0s           | 0             |
+| plugins_loaded:before    |                | 0.1771s | 0.0008s    | 6           | 77.63%      | 59         | 17           | 0s           | 0             |
+| plugins_loaded           | 14             | 0.0887s | 0s         | 0           | 100%        | 104        | 0            | 0s           | 0             |
+| after_setup_theme:before |                | 0.043s  | 0s         | 0           | 100%        | 26         | 0            | 0s           | 0             |
+| init                     | 82             | 0.1569s | 0.0018s    | 7           | 96.88%      | 155        | 5            | 0s           | 0             |
+| wp_loaded:after          |                | 0.027s  | 0s         | 0           |             | 0          | 0            | 0s           | 0             |
++--------------------------+----------------+---------+------------+-------------+-------------+------------+--------------+--------------+---------------+
+| total (7)                | 98             | 0.6575s | 0.0043s    | 14          | 77.42%      | 347        | 26           | 0s           | 0             |
++--------------------------+----------------+---------+------------+-------------+-------------+------------+--------------+--------------+---------------+
+```
+
+Each stage is further segmented by `wp profile` based on its primary actions. For the bootstrap stage, the primary actions include `muplugins_loaded`, `plugins_loaded`, and `init`. You can also see some intermediate actions like `plugins_loaded:before` and `wp_loaded:after`. These intermediate actions correspond to script execution before (or after) actual WordPress hooks. They're pseudo hooks in a sense.
+
+### Step 3 - Profile specific hooks
+
+When you've found a specific hook you'd like to assess, run `wp profile hook <hook>`. Include the `--fields=<fields>` argument to limit output to certain fields.
+
+```
+$ wp profile hook plugins_loaded --url=runcommand.io --fields=callback,time,location
++------------------------------------------------------------+---------+-----------------------------------------------------------------+
+| callback                                                   | time    | location                                                        |
++------------------------------------------------------------+---------+-----------------------------------------------------------------+
+| wp_maybe_load_widgets()                                    | 0.0046s | wp-includes/functions.php:3501                                  |
+| wp_maybe_load_embeds()                                     | 0.0003s | wp-includes/embed.php:162                                       |
+| VaultPress_Hotfixes->protect_jetpack_402_from_oembed_xss() | 0s      | vaultpress/class.vaultpress-hotfixes.php:124                    |
+| _wp_customize_include()                                    | 0s      | wp-includes/theme.php:2052                                      |
+| EasyRecipePlus->pluginsLoaded()                            | 0.0013s | easyrecipeplus/lib/EasyRecipePlus.php:125                       |
+| Gamajo\GenesisHeaderNav\genesis_header_nav_i18n()          | 0.0007s | genesis-header-nav/genesis-header-nav.php:61                    |
+| DS_Public_Post_Preview::init()                             | 0.0001s | public-post-preview/public-post-preview.php:52                  |
+| wpseo_load_textdomain()                                    | 0.0004s | wordpress-seo-premium/wp-seo-main.php:222                       |
+| load_yoast_notifications()                                 | 0.0016s | wordpress-seo-premium/wp-seo-main.php:381                       |
+| wpseo_init()                                               | 0.0329s | wordpress-seo-premium/wp-seo-main.php:240                       |
+| wpseo_premium_init()                                       | 0.0019s | wordpress-seo-premium/wp-seo-premium.php:79                     |
+| wpseo_frontend_init()                                      | 0.0007s | wordpress-seo-premium/wp-seo-main.php:274                       |
+| Black_Studio_TinyMCE_Plugin->load_compatibility()          | 0.0016s | black-studio-tinymce-widget/black-studio-tinymce-widget.php:206 |
+| Jetpack::load_modules()                                    | 0.0564s | jetpack/class.jetpack.php:1672                                  |
++------------------------------------------------------------+---------+-----------------------------------------------------------------+
+| total (14)                                                 | 0.1026s |                                                                 |
++------------------------------------------------------------+---------+-----------------------------------------------------------------+
+```
+
+There you have it! We've discovered that `wpseo_init()` and `Jetpack::load_modules()` are collectively contributing ~100ms to every page load.
+
+With `wp profile`, discovering why WordPress is slow becomes the easy part.