Read-Only Failover

After experiencing an international peering issue that affected some websites for a few hours, we deployed a new experimental service for web hosting named AlwaysUp. This free and optional service can be activated by the customers to ensure their websites will always be accessible. It’s particularly useful for websites that require high read-only availability, such as blogs, magazines, and newspapers. These sites may not be ready to invest in an expensive infrastructure/architecture or in an full-cache CDN, but they can tolerate not being able to edit their content in the event of a failure.

When the service is up, the requests are handled with RR DNS to either the master or the failover, which are geographically distant from each other. The failover proxies the requests to the master and caches them if they don’t include cookies. In case of a failure in reaching the service, the DNS will direct the requests to the failover, which has already cached most of the active pages.


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