The trail names along the side of trails on the map are actually pre-rendered map tile images. These tile images are generated then cached for each zoom level to increase load time and performance.

The app has always used these image labels, but at various times the website has used labels generated in vector text by Mapbox. But the generated labels are much lower quality and MUCH less frequently drawn. So we choose to use the tile image based labels that look better, display better and more often. But have the headache of there updating.

There are several levels of caching, the CDN caches for 6 days, our server caches the tile for 6 days. So it is possible with the correct overlap timing it could take up to 12 days to refresh.

When a trail is updated the system sends a boundingbox to the tile server saying update all tiles in this area. But the server is not able to handle all these requests, its resource intensive. So these requests go into a queue that is slowly worked on one-by-one. The queue is often several thousand items long so it could take several weeks to complete.

And then there is always your local browser cache that might cache tile images. Although it shouldn't cache longer than 6 days since that's what the header maxage is set too.
  • By canadaka Trailforks
  • #75 - 3,841 views