[Geowanking] Terraserver tile caching?

[Russell Nelson]

Andy Armstrong writes:
 > Russell Nelson wrote:
 > > Anybody have an interest in creating a scalable system for Terraserver
 > > tile caching?  Right now I'm just throwing everything into one
 > > directory.  That doesn't scale very well on most filesystems.  For
 > > example, I have 28,351 tiles stored right now, and I can hear the disk
 > > wanking on that directory.
 > 
 > Is this for some code you're writing? Which language?

Mapview.  http://pygps.org/#mapview .  Written in Python, but, really,
the language doesn't really matter.  What's most important is to have
a standard way to translate a Terraserver T=this & S=that into a
filename.  Storing all of the tiles in one directory won't cut it.
Viking, PyTerra, mapview, and terrapaste currently all cache into a
single directory.

I'll propose something:

 1) tiles should be stored in /var/cache/terra.  That directory, and
    all of its children, should have 777 and the sticky bit set, so
    that anybody can store files, but nobody can overwrite files.

 2) the name of a tile should be this, as expressed in Perl:

    "s$(scale)t$(type)z$(zone)/$x/$y"

   or in Python:

    "s$(scale)dt$(type)dz$(zone)d/$(x)d/$(y)d" % locals()

   or in C::

    sprintf("s%dt%dz%d/%d/%d", scale, type, zone, x, y);

 3) Programs automatically create directories as needed.

Comments?

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