[MapProxy] New MapProxy 0.8.3rc1 release

[Oliver Tonnhofer]

Hi,

there is a new release candidate for the upcoming 0.8.3 release of  
MapProxy. Read on for more information.

This release candidate is available at:

     http://mapproxy.org/static/rel/MapProxy-0.8.3rc1.tar.gz

To update within your virtualenv:

$ pip install --no-deps --upgrade \
      http://mapproxy.org/static/rel/MapProxy-0.8.3rc1.tar.gz

Slightly updated documentation is available at:

     http://mapproxy.org/docs/0.8.3.dev-20100430/

Release information
-------------------

The upcoming 0.8.3 release will contain lots of improvements.

Some of the features of the new release:

  - There is a new seed tool that is far more advanced than existing
    tools. See below for more information.

  - There is a new link_single_color_images option for layers. If  
enabled
    MapProxy will not store tiles that only contain a single color as a
    separate file. With the new option MapProxy stores these tiles only
    once and uses links to this file for every occurrence. This can  
reduce
    the size of your tile cache if you have larger areas with no data
    (e.g. water areas, areas with no roads, etc.). This feature is only
    available on Unix since Windows has no support for symbolic links.

  - We have added some performance improvements for servers with  
multiple
    layers and layers with smaller BBOXs.

  - You can configure you own proj4 definition files. For example, if  
you
    need to tweak some projection parameters.


More information about the new seeding tool:

  - Fine control of the seeding area. You are not restricted to BBOX
    anymore and can now load polygons that define the area you want to
    seed. You can load the geometries from text files (WKT) and any data
    source that is supported by OGR (Shapefile, PostGIS, etc.). This can
    reduce the number of tiles to seed dramatically.
    See http://mapproxy.org/docs/0.8.3.dev-20100430/seed.html#geographical-extend

  - Uses multiple processes for the whole seeding chain (request images,
    split, process, encode and store tiles) for better performance on
    multi-core systems. A new --concurrency option lets you define the
    number of processes.

  - New sophisticated seeding strategy. The existing tools (MapProxy,
    TileCache, GeoWebCache) seed from top level to bottom level, from
    north to south, from east to west. This simple strategy works  
against
    the caches of your operating system and database and results in
    unneeded IO load and thus slower seeding performance. If you have
    large datasets your database will have to drop cached data when your
    seeding area moves to the south. When one level is seeded and the
    seeding tool starts in the north of the next level all data cached  
by
    you database and operating system is gone and needs to be loaded  
from
    hard disk again.

    The new seeding tool starts the seeding at the bottom and groups the
    tiles to benefit from the caches of the database and operating
    system. The figure below shows a simple tile pyramid with 3 levels.
    The numbers show the seeding order of every tile.

     level  simple strategy        new strategy

      0            1                    21

      1          2  3                  5 10
                 4  5                 15 20

      2        6  7  8  9            1  2  6  7
              10 11 12 13            3  4  8  9
              14 15 16 17           11 12 16 17
              18 19 20 21           13 14 18 19



We hope you will enjoy the new features.
Any comments are welcomed.

Regards,
Oliver

-- 
Oliver Tonnhofer <olt at omniscale.de>
Omniscale - Dominik Helle, Oliver Tonnhofer GbR
Nadorster Str. 60, 26123 Oldenburg
Tel: +49(0)441/9392774-2 (Fax: 9)