[OSM-dev] rendered

Jon Burgess jburgess777 at googlemail.com
Mon Aug 3 19:17:20 BST 2009


On Mon, 2009-08-03 at 13:55 +0000, John Smith wrote:
> Not sure if it's something I've done wrong or it's supposed to work that way, but after starting rendered it seems to take 2-3 minutes after calling a dirty or unrendered tile before it will respond, but after that it seems to work fine.
> 
> If I wasn't tweaking things in the style sheets it wouldn't matter I guess, but since I'm doing a lot of trial and error blundering about trying to figure it all out it takes a long time to see the result of a little tweak, is there an easy/better way to do this?


The render daemon itself does not have any such delays. I have seen
startup delays like this at other times dues to:

- The data source needing page lots of data into RAM needing lots of
disk IO (e.g. large postgres DB or shapefiles)

- With the postgis data source: setting estimated_extent to false and
not providing a fixed extent for the layer. This causes Mapnik to issue
an extent() query to the DB which normally results in it parsing all the
data to determine the extent.

The second delay is made worse since each thread initializes its own set
of parameters causing this to happen maybe 4 times.

The other issue would be a general slowness if you are trying to process
too much data in your style but this would effect most tiles rendered,
not just he first few.

	Jon






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