Cache Summaries

A cache summary has the following columns:

Component Name

The name of the component that manages the cache. The name is also a link to the component's component browser page, where you can tweak the cache settings. For information about the component browser, see Component Browser. For advice on cache tuning, see Caching. Note that any changes you make to cache settings using the component browser are temporary and will be lost the next time the Content Store is restarted. To make permanent changes to a cache's settings you must edit a .properties file in one of your configuration layers (see Configuring The Content Store).

Size

The maximum number of entries allowed in the cache.

Adds

The number of entries added to the cache since the last restart.

Hits

The number of hits (successful cache look-ups) since the last restart.

Misses

The number of misses (unsuccessful cache look-ups) since the last restart.

Idle

The average time taken for an idle object to pass through the cache, in milliseconds.

Cache Health

A general indicator of how well the cache is performing. The vertical bar shows what proportion of the items in the cache are popular (popular items are ones which keep being requested and therefore stay in the cache for a long time). The green area in the center of the graph indicates the "healthy" area, and the vertical bar should mostly appear within this area. If the indicator is to the left of the green area, then almost all of the objects in the cache are popular. This suggests that the cache may be too small, and there are even more popular objects that cannot be kept in the cache because it keeps filling up. If the indicator is to the right of the green area, then very few of the objects in the cache are popular, suggesting that the cache is larger than it needs to be.

Note that you should not make changes to a cache's size based on a single reading of this indicator. You need to observe the indicator over time, and only make an adjustment if the indicator is consistently outside the healthy area.

LRU Distribution

This graph shows the distribution of items in the cache the last time the cache was full and needed emptying. Each bar represents a level of popularity, so the first bar indicates how many items were very popular (frequently requested), and the last bar shows how many objects were very unpopular. A well-functioning cache should have most items at the left hand (popular) end. If the distribution seems to be completely even it may mean that the cache is too small or too large. Consult Cache Health for further guidance, Idle to see whether or not the cache is retaining items for a sensible amount of time, and Adds to make sure that items are not moving through the cache too fast.

Popularity Distribution

This graph shows the relative popularity of the items in the cache the last time the cache was full and needed emptying. Popular (recently requested) items are shown at the left hand end, unpopular ones at the right hand end. A well-functioning cache should have most items at the left hand (popular) end.

Live hit rate

This shows the percentage hit rate of the cache since the last time the Performance Summary page was updated. In other words, if Auto Refresh is switched on, it shows the hit rate over the preceding 2.5 seconds. If Auto Refresh is switched off then when you click Refresh, it shows the hit rate since the previous time you clicked Refresh.