If you have been using the Machines API recently, you may have seen the support we added for flexible region placement. If you haven’t, it’s simple: You can specify a region preference such as lhr,eu to place a machine in London if possible, otherwise any region in Europe.
This syntax is now also available for request routing. Users of the fly-prefer-region header can now send fly-prefer-region: lhr,eu to prefer London, then prefer Europe, finally routing anywhere if both are unavailable.
This is also available in replays, where the specified region is treated as a “force” rather than a preference. If you replay to lhr,eu the proxy will try London, and failing that force to anywhere in Europe. To make both a preference, you can replay to lhr,eu,any.
As always, drop a comment with any feedback!