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

[Copilot]

Adds Daniel Bachhuber's wp profile tutorial to the handbook as a how-to guide.

Changes

• New guide: how-to/figure-out-why-wordpress-is-slow.md

  • Installation instructions for the wp-cli/profile-command package
  • Profile WordPress load stages with wp profile stage
  • Drill into specific stages using --spotlight flag
  • Identify slow hooks with wp profile hook <hook>

• Manifest registration: Added entry in bin/handbook-manifest.json

• Index update: Linked guide from how-to.md

Example workflow

# Install the profile command package
$ wp package install wp-cli/profile-command

# See metrics for each load stage
$ wp profile stage --url=example.com

# Drill into slow bootstrap stage
$ wp profile stage bootstrap --spotlight

# Profile specific hook callbacks
$ wp profile hook plugins_loaded --fields=callback,time,location

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add how-to guide: "Figure out why WordPress is slow"</issue_title>
<issue_description>Let's get Daniel's now deleted blog post into the handbook:

Figure out why WordPress is slow with wp profile
With wp profile, you gain quick visibility into key performance metrics (execution time, query count, cache hit/miss ratio, etc.) to guide further debugging.

November 3, 2016
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.

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.
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             |
+--------------------------+----------------+---------+------------+-------------+-------------+------------+---...

</details>



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- Fixes wp-cli/handbook#615

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