[OSM-talk] [OSM-dev] Software development - most pressing issues

[Robert (Jamie) Munro]

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Tom Hughes wrote:
> In message <474EE4A0.8070201 at arjam.net>
>         Robert Munro <rjmunro at arjam.net> wrote:
> 
>> This should be fairly simple:
>>
>> 1. Figure out how to efficiently apply osmosis changesets to the postgis
>> database (probably based on keeping a copy of the OSM database using
>> osm2pgsql's database intermediate storage thing, then maybe using
>> triggers to pass changes to the postgis geometry tables)
>> 2. Figure out which tiles have been changed in the osmosis changeset and
>> expunge them from the cache.
>> 3. Repeat hourly
> 
> You seem to have forgotten to rerender the tiles - just flushing as
> bad as it means people will get the "here be dragons" tile until such
> time as the tile is rerendered.
> 
> The current scheme largely never flushes - it just marks as dirty so
> that they are (in due course) rerendered and until then it continues
> to serve the old ones as that is better than a "coming soon" tile.

Mark them dirty rather than flushing is an improvement, yes. But
currently, AFAIK, it marks all tiles as dirty once a week (or something
like that) weather they have changed or not. If it didn't do this, the
backlog could be reduced.

What happened to the live on-demand rendering of tiles? I think it
should try to render tiles that people are wanting to see now ahead of
tiles in the backlog. It should only look at the backlog if it is not
busy rendering current requests.

Random other thought: Have we tried removing the highest 2 levels of
zoom from the backlog? I.e. only ever show them rendered live? They
would take up something 3/4 of the storage, but each tile individually
is very unlikely to ever be looked at. They are also the fastest to
rerender.

Robert (Jamie) Munro
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