LudicrousDB & dotenv

LudicrousDB is a WordPress plugin, which allows splitting the database tables of a Network into multiple chucks (called shards) and use multiple database servers.

By default WordPress stores is database-configuration in a PHP-file called wp-config.php.

To avoid mixing code with config (like a proper 12factor-app) we use a separate file (.env or dotenv) to split code from configuration. This approach is used also by LEMP Stacks like Roots Trellis.

This repository uses an .env file to configure LudicrousDB in a simple (and quite basic) manner.

---

• ❗ This is not your default WordPress - Plugin. There are some setup-steps required.
• ❗ This is a very basic implementation. It only supports a small subset of the features LudicrousDB offers. PRs are welcome :)
• ❗ Use at your own risk. Create backups before you use this!
• ❗ Sadly WP-CLI does not properly support sharding with LudicrousDB. It only lists tables from the first 'global' shard with --all-tables. When you currently wp db export --all-tables you only tables from your primary shard.
• ❗ Does not support replication (yet).

Setup

1. Go ahead and get LudicrousDB running. One of the steps there is putting a file called db.php into the WP_CONTENT_DIR (more about WP Directories) and a db-config.php next to your wp-config.php (this is all describe in the LudicrousDB ducumentation).

   • db.php
     • loads mu-plugins/ludicrousdb/ludicrousdb.php
       • loads ./includes/functions.php
         • loads ABSPATH . db-config.php

2. Add the following to your db-config.php

	$ludic_defaults = array(
		'host'     => DB_HOST,
		'user'     => DB_USER,
		'password' => DB_PASSWORD,
		'name'     => DB_NAME,
		'write'    => 1,
		'read'     => 1,
		'dataset'  => 'global', // default is global.
	);

	$wpdb->add_database( $ludic_defaults );

	// path to the ludicrousdb-dotenv-plugin.
	require_once WP_CONTENT_DIR . '/mu-plugins/ludicrousdb-dotenv/ludicrousdb-dotenv.php';
	$ludic_dotenv = new Ludicrousdb_Dotenv( $ludic_defaults );

3. Setup your .env-file (see below in examples). If you don't touch your .env everything should still be running.
4. Run wp-cli commands, to prepare all databases.

Examples

Example 1

We want to scale a lot. We set up some bigger amount of shards, so we can later split them.

First specify the amount of databases you want for your 'dataset' (BLOG used as example here)

# .env
# The amount of shards you want for your blogs.
DB_BLOG_COUNT = 256
# Specify details for a specific blog:

# DB_BLOG_126_USER = DB_USER <- this is automatically inherited from WP-defaults
DB_BLOG_127_USER = 'example_user' # username for the database
DB_BLOG_127_WRITE = 0
# DB_BLOG_128_USER = 'example_user' <- 'example_user' is automatically inherited from the previous entry (127)

Values are inherited from the previous entry (from the same 'dataset')

Example 2

I just want to store my blogs in a different database, so they are separated from the global ones.

# .env
# give me a single shard for all blogs.
DB_BLOG_COUNT = 1
# You could specify another host. or another user.
# DB_BLOG_0_HOST = 'example_user' # username for the database

Now run the following wp-cli commands (on your own risk ;)

# create the databases (the default for this is spaces_development_blog_shard_0)
# you might have to use a different sql-user, who is allowed to create databases with --db_user=... --db_password=...
wp ludicrousdb_dotenv create_databases

# copy the tables to your shard(s). mysql and mysqldump have to be installed.
wp ludicrousdb_dotenv copy_tables_to_shards

Note

• Things in the .env file are all uppercase, anything else is lowercase.
• In case of blog shards we use the same name for the database as for the dataset.
• Config starts form 0. So the first shard is DB_BLOG_0_... .

Todos

• think about adding a slave to a specific blog.
• we could also move the root-blog which is difficult because wpdb->get_blog_prefix (blog_id 1 has no prefix).*
• More backend interfaces to find blogs.
• WP-CLI export is not working, as it doesn't respect custom db.php. Make a PR to WP-CLI to support sharding.