Script to invalidate Redis cache in Wordpress after adding new blog posts and such. To be used with https://gist.github.com/hans2103/5657621 where you already defined the connection information to Redis.

rediscacheinvalidation.php

<?php
/*
   Redis Cache invalidation
   Author: Flynsarmy and modified by Hans2103
   This is a Redis Cache invalidation script for Wordpress.
   http://www.flynsarmy.com/2013/03/how-to-drastically-speed-up-wordpress-with-redis/
   defined the connection credentials in wp-config.php
   
   Add this piece of code to your theme functions.php or...
   when using Roots theme add this as a file to the lib directory and call it from functions.php
 */
 
define('R_SERVER', '<servername>');                  // The server of your Redis database
define('R_PORT', <portnumber>);                            // The port to your Redis server
define('R_PASSWORD', '<password>');  // ...and password
define('R_PREFIX_KEY', '');                         // Redis key prefix
 
function get_redis()
{
  // Redis connection information
  // defined in wp-config.php
	$redis = new Redis();
	$redis->connect(R_SERVER,R_PORT,2.5);
	$redis->auth(R_PASSWORD);
	return $redis;
}
 
// Chances are you'll have a list of categories on every page.
// So delete all site cache if categories are messed with
add_action('add_category', 'redis_invalidate_all');
add_action('delete_category', 'redis_invalidate_all');
add_action('edit_category', 'redis_invalidate_all');

// Delete all site cache for the current domain
function redis_invalidate_all()
{
	$redis = get_redis();
 
 	$redis->flushdb();
 	
	/*$domain = $_SERVER['HTTP_HOST'];
	$dkey = md5($domain);
	if ( $redis->exists($dkey) )
		$redis->del($dkey);*/
}
 
// When adding/editing/deleting a post, invalidate post and home pages
add_action('trashed_post', 'redis_invalidate_post');
add_action('save_post', 'redis_invalidate_post');
add_action('publish_post', 'redis_invalidate_post');
add_action('edit_post', 'redis_invalidate_post');
add_action('pre_post_update', 'redis_invalidate_post');

function redis_invalidate_post( $post_id )
{
	// Don't delete cache on auto-save
	if ( isset($_POST['action']) && $_POST['action'] == 'autosave' )
		return;
 
	// Don't delete cache if we're saving as draft or pending
	if ( isset($_POST['save']) && in_array($_POST['save'], array('Save Draft', 'Save as Pending')) )
		return;
 
	$redis = get_redis();
 
	$domain = $_SERVER['HTTP_HOST'];
	$dkey = md5($domain);

	// Invalidate homepage
  //$ukey = md5("http://".$_SERVER['HTTP_HOST'].'/');
	$ukey = md5(site_url().'/');
	if ( $redis->hexists(R_PREFIX_KEY.$ukey, $dkey) )
		$redis->hdel(R_PREFIX_KEY.$ukey, $dkey);
		
	// Invalidate post page
	$ukey = md5($permalink = get_permalink( $post_id ));
	if ( $redis->hexists(R_PREFIX_KEY.$ukey, $dkey) )
		$redis->hdel(R_PREFIX_KEY.$ukey, $dkey);
}
 
// When adding/editing/deleting a comment, invalidate post and home pages
add_action('comment_closed', 'redis_invalidate_comment');
add_action('comment_post', 'redis_invalidate_comment');
add_action('edit_comment', 'redis_invalidate_comment');
add_action('delete_comment', 'redis_invalidate_comment');
add_action('wp_set_comment_status', 'redis_invalidate_comment');

function redis_invalidate_comment( $comment_id )
{
	$comment = get_comment( $comment_id );
	redis_invalidate_post( $comment->comment_post_ID );
}