A recent hardware issue on the Arctic Web Map Tile Server caused a short outage earlier this week. As February 15 was a public holiday, the outage lasted 23 hours and was corrected on February 16.
To maintain some availability of Arctic Web Map tiles during any future Tile Server issues, I have set up a tile caching server in front of the Arctic Web Map Tile Server. This cache server is hosted with Cybera in Calgary, on a separate infrastructure system than Arctic Web Map which is hosted at the nearby University of Calgary.
In this new setup, when requests are made for a tile they are passed through this cache server to the main tile server and the result is cached in a disk store on the cache server. If a subsequent request is made for the same tile and the tile has not past its expiry date, then the cache server will return its local copy instead of asking for a copy from the tile server.
If the tile server is unavailable, then the cache server will return a local tile to you if there is one in the cache. Otherwise, a 504 error is returned. Currently the cache server will wait up to 3 seconds to open a connection to the tile server. If the tile server does not respond at all, then it will be considered unavailable for that request. This does not affect cases where the tile server is online and a new tile needs to be rendered, but takes more than 3 seconds to generate: in that case, the cache server will still open a connection within the 3 second limit.
You do not need to do anything to use this new service as it was activated automatically when I switched the DNS to point *.tiles.arcticconnect.org to the cache server today (February 17).