[OSM-talk] Map tiles in Chrome

David Earl david at frankieandshadow.com
Fri Oct 21 14:58:16 BST 2011


I'm very puzzled by Chrome's behaviour with respect to the main Mapnik 
map tiles.

When I'm working on an area, it is very common for a tile not to visibly 
update after refreshing after uploading some changes. Some do, some 
don't, especially at high zoom levels

When I do a status on the tile, it is clear it has been re-rendered. 
It's not that it is stuck in a rendering queue - the renderer has finished.

If I clear the Chrome cache, it still doesn't drop the old rendering.

If I drop the Chrome cache and restart Chrome it still doesn't let go.

The only way I have found that is certain to display the new tile is:
1. Right Click on the tile in the home page and choose 'Show image in 
now tab'
2. Go to the new tab, and hard refresh (CTRL+F5)
3. Restart chrome

(a hard refresh or a click on Permalink after step 2 isn't sufficient).

So what's going on? If the cache is empty, is the server really serving 
an old tile? Is there some proxying going on somewhere (there's no 
explicit proxies)? Why is it random which tiles update?

More to the point, why should I need to do anything with the 
cache/refreshing etc. Why isn't the date handling from the server 
telling Chrome the tile is out of date? I see the headers have an expiry 
date with the tile, but the old tile seems to persist even beyond that.

David





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