CDN nodes are usually used in a website to achieve content distribution after acceleration, when the source station updated content, refresh the CDN system will refresh request will specify the contents of the cache on the CDN node forced by submitting expired. When the user access, CDN node back to the source to obtain the latest content back to the user, and update the resource cache node. Traditional CDN refresh usually takes a few minutes to take effect, and as the number of service nodes and form, the effective time will be longer linear.
In this case will encounter these problems: When the media website published an article there is error, because the system is slow to refresh, the first time can not be amended or withdrawn; electricity supplier during the large-scale promotional activities, product activity details page the pictures need real-time updates in a timely manner because they can not refresh CDN cache, the latest details page can not update the first time to the whole network, may affect a single user. Above such questions could bring some credibility or loss of business.
There is no doubt, want to avoid the above problems, CDN systems need to refresh to refresh the cache CDN node after the source station updates to ensure that the contents of the source station with CDN caching content as consistent as possible.
In fact, Ali cloud CDN per day over one million domain names accelerating, undertake billions of refresh, you want to break the barriers of conventional refresh rate, we will face several technical challenges :
First, real-time , in such a large amount of background data, the need to address how to quickly spread the word to the whole network issues
second, reliability , under the complex network of public transport links, we need to effectively deal with network congestion, ensure low latency and stability of the transmission of
the third, scalability , with the increase in business growth, CDN node, to resolve the long linear growth problems will not refresh, refresh rates remained without performing center expansion, provided "no sense" refreshing experience
For more than a few technical difficulties, Ali cloud CDN technical team with extensive protocol optimization practice, and finally reach a breakthrough to achieve a whole network average refresh time down to the millisecond take effect . That is when the customer changes the contents of the source station, less than a second time, all network users can already access to the latest content. The system enables true exponential news broadcasts, can effectively deal with information systems refresh slowly brought not updating other issues, greatly enhance the entire network refresh rate customer content, thereby enhancing users access experience. At the same time, refresh the system uses log (n) base (a) the convergence rate, can be done at the level of tens of thousands of nodes refresh time still remain in milliseconds, not linear growth, protect the whole network in the rapid growth of the service node refresh . The follow-up capabilities for Ali cloud CDN customers will open.
In addition, Ali goes global CDN there are 2500 nodes, 120T bandwidth of reserves, relying CDN intelligent scheduling systems, precision controlled water level prediction technology, security, and other full-link disaster recovery capabilities, time and time again withstood 11 double party, Spring Festival live Internet broadcast and other large trials, and to assume 70% of the entire network traffic during the World Cup last summer World Cup in Russia.
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