[mapguide-users] MapGuide Open Source 3.0 Beta 1 released

[Jackie Ng]

I'd thought the "3.0" milestone and the "completed" status on that RFC
would've hinted the state of this new feature :)

This is not yet tested, but if you make a new TileSetDefinition using the
default provider with the same layer/group structure and finite scale list
and point its tile cache path to where your old tiles are located, it should
theoretically continue to serve out any cached tiles from that old location
(and put any new tiles in there) should you do GETTILE requests through the
new TileSetDefinition.

As mentioned in the RFC, tile caches can still be wiped if you save the
TileSetDefinition itself. However, if you save a Map Definition that links
to a TileSetDefinition, that tile cache *should not* be wiped out. This is
one of the many benefits of separating the tile set stuff out into its own
resource. Now if while testing this beta release you find out what I just
said is false (ie. The tile cache is being wiped when you are saving
something other than the TileSetDefinition), then this is a bug that should
be reported and resolved ASAP.

Another thing about the XYZ provider that I didn't really explain in the
blog post is that it uses a {z}/{x}/{y} physical directory structure for its
tile storage. So if you wanted to, you could easily map a fully seeded XYZ
tile cache directory in your web server of choice and easily consume these
tiles directly via OpenLayers/Leaflet/etc with full cache headers and other
goodness that a web server would normally apply for static content that is
served out.

The flagrant tile set invalidation problem itself is not solved for this
milestone. I have a few ideas:

 * APIs to "lock" tile sets to prevent edits on upstream dependent
resources.
 * Only triggering tile cache invalidation on changes of certain XML content
on upstream resources (eg. The VectorScaleRange section of the Layer
Definition). This way, layer changes that do not affect how a tile would
look (anything not related to styles), won't trigger a blow up of the tile
cache.
 * A hybrid of the above two solutions, where a locked tile set will prevent
edits to style settings in any upstream Layer Definition but anything else
goes through.

I've yet to explore any of these ideas to determine feasibility.

That's pretty much all the "gotchas" to be aware of.

- Jackie



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