[OSM-dev] mod_tile configuration question

[Phil! Gold]

* Nonmaskable Interrupt <nmi8080 at gmail.com> [2012-04-20 12:26 -0400]:
> Hi.  I have a private mod_tile server that has database performance
> problems generating zoomed out tiles.  Since I am not updating my
> database frequently, what would I need to do to keep the cache from
> ever automatically expiring tiles?  Also, is there a way to prerender
> all tiles for several of the zoomed out levels automatically?

Here's what I've done:

I use `render_expired` to expire tiles with the following command line:

    render_expired --min-zoom=11 --max-zoom=18 --touch-from=11 --delete-from=17

(Plus other appropriate options for my setup, like --map.)  That ensures
that tiles from zoom 10 and below don't get automatically expired, so they
don't get rerendered every time someone visits one.  (The main OSM map
ignores everything from zoom 12 down, which seems to me to be a good
policy for a widely-used tileserver.)

I'm using tirex to do the rendering, so I just set up an appropriately
low-priority queue and used `tirex-batch` to queue up all the low zoom
tiles.  I'm not sure what the equivalent machanism for mod_tile's renderd
is.  I also had to change tirex's master_rendering_timeout and
backend_manager_alive_timeout settings because the defaults were too small
for my rendering; I was getting a lot of zoom 7 and 8 tiles that always
timed out when it tried to render them.  I set the variables to 60 and 55,
respectively, which has worked for my system.

-- 
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