Redis Cache By Xon 2.18.3

• Work-around for buggy browsers failing to request css URLs properly

• Remove "Disable individual css cache" option.
  • While the xf_css_cache table is subject to 'thundering herd' issues; it still provides a benefit during cache rebuilds and the frequent invalidation is a XF issue with it's usage
• Implement short (~5 minute) caching of individual css templates & parse_less_color/parse_less_func functions (parse_less_func is from Advanced BbCodes Pack). Minor, but measurable performance improvement
  • When caching is enabled, this hits redis instead of the xf_css_cache table.

• On Style changes, adjust expiry to keep redis memory usage from ballooning

• Support for phpredis extension v5
• Add options icon

• Remove "Count Moderated Threads" option (caching should automatically be per-user now)
• Simplify Thread list count caching to be more robust

• Re-organise example config to be per-purpose, no actual changes to add-on itself

• Workaround for persistent connections and XF2.1 page cache feature causing login failures when using multiple databases in the same redis instance.
• Track latest upstream Credis library

• Enable LUA by default (all Redis versions since v2.8 have supported LUA scripting)
• Multi-DB support when counting keys in Redis instamce
• Support being a drop in replacement for the stock Redis provider
  • Alias the config key "host" to "server"

Thanks to @DragonByte Tech for contributions

• Update layout of master Redis server to match server environment report
• Include free/peak/max memory usage in stats output

• New option to default disable XenForo's individual templating css caching.
  • XenForo2 provides per-template css caching which is vulnerable to "thundering herd" cache slamming by introducing unexpected write load which is vulnerable to MySQL locking via insert ... on duplicate key update.
  • This is only an issue for sites which experience large numbers of concurrent users
  • The full CSS output is still cached by whatever caching layer is defined, which saves vastly more time than individual template caching.