Differences between Data Cached and Data Non-Cached
You may have noticed that there are two type of data in our reports - Data Cached and Data Non-Cached. For example the following chart can be seen when you purge content from your CDN service.
Data Cached represent data requested by your end-users and served from the CDN cache.
Data Non-Cached represent data requested by your end-users which were missing in the CDN cache. Please note that the data were automatically pulled from the origin server by the corresponding CDN edge server, then served to your end-users and then possibly stored in the CDN cache.
Cache Hit Ratio
Cache Hit Ratio represents the following ratio.
Data Cached / (Data Cached + Data Non-Cached)
Streaming CDN service
If you have a streaming CDN service (CDN Video, CDN Video Push or CDN Live) then all traffic is counted in Data Non-Cached. In the case of CDN Video and CDN Video Push services your video files are cached on CDN edge servers but still the traffic is counted in Data Non-Cached. Please refer here for more details.
Please note that all remaining examples apply to CDN Static and CDN Static Push services only.
New origin content
When you add new content to the origin server then it is missing in the CDN cache. If it is requested by your end-users via a CDN URL (or you prefetch it) then as explained above the content is automatically pulled from the origin server by the corresponding CDN edge server and then served to your end-users. Based on HTTP headers received from the origin server the content is or is not stored in the CDN cache (on edge server SSD drives) for subsequent requests. In this case the traffic from the CDN edge server to your end-users is counted in Data Non-Cached and the traffic from the origin server to the CDN edge server is not displayed in our reports and is free of charge.
Expired CDN content
Redirect on Origin Domain
Let's assume that your Origin Domain (mycompany.com) redirects (3xx response code) to some other domain (for example to www.mycompany.com). Please note that in this case your CDN service will redirect to www.mycompany.com also. In particular requests via CDN URLs will be served from your server via www.mycompany.com and you will not be using CDN. This traffic is counted in Data Non-Cached. Please note that to solve the "redirect problem" you need to make sure that your Origin Domain returns only 200 HTTP response codes.
Caching disabled on origin
Caching can be completely disabled on the origin server using cache control HTTP headers. In this case all traffic is counted in Data Non-Cached.
What happens to a CDN service if its origin fails?
The answer depends on the CDN service type.
- CDN Live - the CDN service fails.
- CDN Video or CDN Video Push - the CDN service fails.
- CDN Static or CDN Static Push - a high percentage of requests to your CDN service respond normally for some time. Good estimate for the percentage is your cache-hit ratio and the time closely corresponds to the cache expiry time of your content.
Read about the following topics.