Page Cache Hit Rates
| This feature is only available starting with Tideways Daemon version 1.8.12 and PHP extension 5.5.8 released in September 2022 and requires the latest subscription plan. |
It is common for PHP applications to implement some concept of full page caching, storing the full HTML or API response in a cache, instead of recomputing it including potentially expensive database operations.
Full page caches can be implemented with reverse proxies such as Varnish, but for best flexibility they are often fully implemented in PHP.
Tideways supports computing the page cache hit ratios for PHP-based caching systems. These are calculated both on the service- and on the transaction-level.
As soon as requests are marked as cached or uncached by the PHP extension, the Page Cache Hit Rate is shown as a primary metric for the current time frame in the monitoring screen of services and transactions.
In addition to the realtime data, there is an observation for the page cache hit rate calculated once every day for the historical performance. When the hit rate goes below 70% a warning is issued, and for below 50% an error is issued. Page cache hit rates really should be high for the cache to be efficient.