#Mpchadwick_PageCacheHitRate

Hit rate tracking for Magento Page Cache.

###Configuration

All configuration is done through an XML file in the /app/etc directory. This is because module configuration is not loaded in the case of a full hit. mpchadwick_pagecachehitrate.xml.template is included with example settings. A few notes...

• Mpchadwick_PageCacheHitRate_Model_Processor is added as a <request_processor>.
  • Note: request_processors are loaded alphabetically based on the file name in /app/etc. It is important that Mpchadwick_PageCacheHitRate_Model_Processor be the final request_processor to know for sure if this is a full hit. By default the Enterprise_PageCache_Model_Processor is defined in enterprise.xml and will be loaded first, however if your are using something else to process the result of Enterprise_PageCache_Model_Processor you may need to change the file name in /app/etc.
• <tracker>s can be configured in your <full_page_cache> configuration under the <mpchadwick_pagecachehitrate> node. If no trackers are specified, hit rate will not be tracked.
• There is a <track_container_misses> setting which can be used to track individual container misses in the case of partial page hits.
• A <metadata_source> can be configured under the <full_page_cache> configuration in the case where Enterprise_PageCache_Model_Processor is not the correct class to provide metadata. This can happen if the <ee> request processor is changed, notably with Elastera_EnterprisePageCache.

###Trackers

The following trackers are available...

• Mpchadwick_PageCacheHitRate_Model_Tracker_File A log file will be used for for tracking hit rate. A new file will be created each day.
• Mpchadwick_PageCacheHitRate_Model_Tracker_NewRelic New Relic custom events will be used for tracking hit rate.
• Mpchadwick_PageCacheHitRate_Model_Tracker_Redis Hit rate will be tracked in Redis. The intention is to scrape this data periodically and store it in a tool such as InfluxDb or Prometheus.

You can easily create your own tracker if you'd prefer a different means of tracking. Simply implement the Mpchadwick_PageCacheHitRate_Model_TrackerInterface interface and configure your class as the <tracker> in an xml file in /app/etc.

###Dimensions

In addition to a full hit and a full miss, Enterprise_PageCache can also have partial hits. This happens if a cached response is found, but it has containers that need additional processing. The type metric is thus tracked as either a hit, a miss, or a partial.

In addition to type, the following dimensions are tracked...

• route,
• url
• ip
• hostname
• customerGroup

For example, you may want to see your cache hit rate for a single route such as /catalog/product/view or know your cache hit rate for a single IP address if your are seeing crawling / bot activity creating performance impact on your site.

Here are some example entries using the Mpchadwick_PageCacheHitRate_Model_Tracker_File tracker...

2016-06-02T02:28:04+00:00 DEBUG (7): {"url":"http:\/\/magento-1_14_1_0.dev\/men\/shirts.html","ip":"172.16.9.1","type":"miss","route":"catalog\/category\/view"}
2016-06-02T02:28:09+00:00 DEBUG (7): {"url":"http:\/\/magento-1_14_1_0.dev\/men\/shirts.html","ip":"172.16.9.1","type":"partial","route":"catalog\/category\/view"}
2016-06-02T02:28:11+00:00 DEBUG (7): {"url":"http:\/\/magento-1_14_1_0.dev\/men\/shirts.html","ip":"172.16.9.1","type":"hit","route":"catalog\/category\/view"}

Container misses will be recorded to a separate file (if enabled). The entries will look like this...

2016-06-02T03:18:14+00:00 DEBUG (7): {"url":"http:\/\/magento-1_14_1_0.dev\/women\/women-new-arrivals.html","ip":"172.16.9.1","route":"catalog\/category\/view","container":"Enterprise_PageCache_Model_Container_Catalognavigation"}

Also note that you can configure multiple trackers. You may want to store data in both New Relic and Redis, for example.

###Cardinality

By default, highly cardinal dimensions are tracked such as IP address and URL. For the Mpchadwick_PageCacheHitRate_Model_Tracker_File and Mpchadwick_PageCacheHitRate_Model_Tracker_NewRelic trackers this is probably fine. However if you are using Mpchadwick_PageCacheHitRate_Model_Tracker_Redis and sending the data to InfluxDb or Prometheus you'll probably want to decrease the cardinality of the data.

You can specify dimensions to strip on a per tracker-basis. E.g...

<config>
    <global>
        <full_page_cache>
            <mpchadwick_pagecachehitrate>
                <trackers>
                    <redis>
                        <class>Mpchadwick_PageCacheHitRate_Model_Tracker_Redis</class>
                        <server>127.0.0.1</server>
                        <port>6379</port>
                        <database>1</database>
                        <strip>
                            <ip />
                            <url />
                        </strip>
                    </redis>
                </trackers>
            </mpchadwick_pagecachehitrate>
        </full_page_cache>
    </global>
</config>