Integrated Cache Test

Ideally, the value of this measure should be high.

Ideally, the value of this measure should be 0 or much lower than the value of the Hits measure. A very high value is a cause for concern as it indicates that the cache is poorly utilized.

This is the sum of the values of the Hits and Misses measures.

Ideally, the value of this measure should be 80% and above. A value lesser than 80% indicates that the cache is unable to service many requests, maybe because the objects requested are not in cache. This could be due to poor cache size. 

The integrated cache saves bandwidth by servicing requests that would otherwise have fetched data from the origin server and consumed considerable bandwidth resources in the process.

This is why, the value of this measure should be high, ideally.

A very low value indicates excessive bandwidth consumption and abysmal bandwidth saving owing to the inability of the cache to service majority of the requests. 

A 304 status code indicates that a response has not been modified since the last time it was served.

Ideally, the value of this measure should be close to 100%.

A value close to 100% is desired for this measure.

If compression is On in the ADC, this ratio may not reflect the bytes served by the compression module. If the compression is Off, this ratio is the same the ratio of the Origin bandwidth saved.

A high value is desired for this measure, as it may reduce cache misses going forward.

Ideally, the value of this measure should be 0. This is because, non-storable misses are inappropriate for caching. By default, any response that contains the following status codes is a non-storable cache miss:

201, 202, 204, 205, 206 status codes

All 4xx codes, except 403, 404 and 410

5xx status codes

Max-Age setting in a Cache-Control header determines, in number of seconds, when an intervening cache must revalidate the content with the integrated cache before serving it to the user.

The value of this measure signifies the number of times the Max-Age setting was violated, causing revalidation to be attempted.

Ideally, the value of this measure should be the same as the value of the Revalidations measure.

You can configure the ADC appliance to always consult the origin server before serving a stored response. This is known as Poll Every Time (PET). When the ADC appliance consults the origin server and the PET response has not expired, a full response from the origin server does not overwrite cached content. This property is useful when serving client-specific content. After a PET response expires, the ADC appliance refreshes it when the first full response arrives from the origin server.

A client issues a conditional request to ensure that the response that it has is the most recent copy. A user-agent request for a cached PET response is always converted to a conditional request and sent to the origin server. A conditional request has validators in If-Modified-Since or If-None-Match headers. The If-Modified-Since header contains the time from the Last-Modified header. An If-None-Match header contains the response's ETag header value.

If the client's copy of the response is fresh, the origin server replies with 304 Not Modified. If the copy is stale, a conditional response generates a 200 OK that contains the entire response.

Higher the value of this measure, lesser will be the count of cache misses going forward. A value close to 100% will be ideal.

The value 100% will be ideal for this measure.

The phenomenon of Flash crowds occurs when a large number of clients access the same content. The result is a sudden surge in traffic toward the server. The Flash Cache feature enables the ADC appliance to improve performance in such situations by sending only one request to the server. All other requests are queued on the appliance and the single response is served to all of the requests.

Ideally, the value of this measure should be 0.

Ideally, the value of this measure should be high.

Policies enable the integrated cache to determine whether to try to serve a response from the cache or the origin.

Actions determine what the ADC appliance does when traffic matches a policy.

Policies that you associate with the INVAL action for instance, immediately expire cached responses and refresh them from the origin server.

An invalidation selector/parameter in a content group is a filter that locates particular objects in a content group that need to be expired.

The value of this measure represents the number of requests that match an invalidation policy configured with an invalidation selector or parameter. A non-zero value for this measure indicates that one/more responses in the content group match the invalidation selector/parameter specification in the invalidation policy and have hence been expired. 

The invalGroups parameter in an INVAL policy configuration indicates the content groups to be invalidated/expired.

A non-zero value for this measure therefore indicates that content groups configured for invalidation have been found and have been expired.

A non-zero value for this measure indicates that content groups and/or one/more responses in content groups have been found to be match with configured invalidation policies and the matching groups/responses have been expired.

You can configure the ADC appliance to always consult the origin server before serving a stored response. This is known as Poll Every Time (PET). When the ADC appliance consults the origin server and the PET response has not expired, a full response from the origin server does not overwrite cached content. This property is useful when serving client-specific content.

After a PET response expires, the ADC appliance refreshes it when the first full response arrives from the origin server.

A high value is desired for this measure.

Typically, up to 50% of memory available to the ADC appliance can be allocated for caching. If the global memory limit of the cache is set to 0, it indicates that the integrated cache feature is disabled.

Once the global memory limit is set, you can reset it to any other positive value later. However, this change will not alter the existing memory allocation to the Integrated cache immediately. For instance, you can change the global memory limit from 4000 MB to 6000 MB. But, if you query the memory limit soon after, you will find that while  the Maximum memory measure reports the new memory limit of 6000 MB, the actual memory usage limit in effect currently continues to be 4000 MB and is by Maximum memory active measure. To ensure that the change to the global memory limit is effected, save the new configuration and restart the appliance. Once this is done, then before the Maximum memory and Maximum memory active measures will report the same value.

If the value of this measure is very close to the Maximum memory active measure, it indicates that the cache is running out of memory and will not be able to hold any more requested objects.  This will drastically reduce cache hits and increase cache misses. Also, accesses to the origin server will increase, thereby adversely impacting bandwidth usage.

Under such circumstances, you may want to consider resizing the cache by allocating more memory to it. 

Ideally, the value of this measure should be 0. A high value for this measure could indicate that the cache does not have adequate memory to allocate for responses. In such a situation, consider resizing the cache by allocating more memory to it.

One of the reasons for a memory drain on the cache is the presence of too many objects in the cache. Whenever Memory allocation failures are high, check the value of this measure to figure out if too many objects have been cached.

Marker objects are created when a response exceeds the maximum or minimum size for entries in its content group or has not yet received the minimum number of hits required for items in its content group.

Though a marker object is cacheable, it will not be cached until it meets the configured maximum or minimum size specification or the minimum number of hits specification.

If too many cache misses occur because of a marker object, you may want to change the Minimum Response Size, Maximum Response Size, and/or the MinHits for the content group.