Origin offload, or the percentage of end-user requests that reach the origin servers from the Akamai Edge, is a critical number for all our customers. It indicates how much content caching happens at the Edge, yielding improved user experience via shorter latencies and cost saving for the origin infrastructure.
This number can be retrieved from the Luna Control Center menu MONITOR->Offload:
The seemingly precise question “what is a good offload number” actually needs to be broken down into two separate pieces:
1) For the resources that are cached at the Akamai Edge (TTL > 0) what should the expected offload be? In other words, what is the effectiveness of the Edge caching?
2) Taking all the resources into consideration, the no-store and the cached ones, what is the overall offload for my website?
Regarding the first question (1), what drives the origin offload are:
- The resource global popularity, i.e. how many requests hit the Akamai servers per unit of time
- The Edge TTL (obviously …) It is the one parameter you can directly control
- The traffic distribution. Everything else being equal, if all the requests happen to hit the very same edge server, the offload will be better than if each request hit a different edge server.
For popular resources, even short TTLs (< 1 min) can yield very good offload numbers (> 95 %) as explained in aseparate post. For content that is both popular and can bear a long TTL (one day or more), it is not unusual to see offload close to 100%.
In short, if you witness anything below 95% for cached resources it is likely due to the following:
- Variable query parameters that ‘bust’ the cache unnecessarily. This can be remediated by ignoring such parameters in the cache-key definition
- Long tail items, like search results or individual product pages. You may want to consider increasing the TTL for these use cases, whenever possible
As for the second question (2), since the static content is typically highly cached, it can be formulated as “what is a good proportion of dynamic (= non-cacheable) requests for my website as a whole?”
The answer to this one is highly dependent on the application. If your web pages primarily report personalized and real-time information, the expected overall offload ought to be very different from a website displaying popular stock photographs!
If your site sits in between, and the majority of the websites we serve do, then from my experience anything over 80% can be considered good. If your overall offload (taking all the cpcodes into account) falls below this mark, consult with your Akamai team. We will help you squeeze more offload out of your websites by identifying resources that were initially deemed uncacheable, starting with your home page!
No comments:
Post a Comment