MapGuide RFC 90 - Meta Tiling Support

This page contains an change request (RFC) for the MapGuide Open Source project. More MapGuide RFCs can be found on the RFCs page.

Status

RFC Template Version	(1.0)
Submission Date	(Date/Time submitted)
Last Modified	(your name here) Timestamp
Author	Zac Spitzer, Uv
RFC Status	(draft)
Implementation Status	(testing sandbox)
Proposed Milestone	(2.2)
Assigned PSC guide(s)	(when determined)
Voting History	(vote date)
no vote

Overview

Add support internally to the MapGuide Server Engine to render larger tiles and then slice them up into the normal tile sizes

Motivation

With complex maps, it's more efficent to render one large tile than many small ones. There is little or no benefit for simple maps like the Sheboygan Sample.

Using our 140 layer example map we can observer the following timing using metatilefactor 1 & 4 and 3 different locking strategies:

[[Image:MetatilingChart1.jpg|frameless|upright|left]]

Proposed Solution

Add a meta tile factor to the tile service, which then will render larger tiles and then slice them up into the smaller tiles which get served to clients.

Implications

The current approach with polling for lock files is inefficent and is excaerbated by meta tiling. When using a meta tiling factor of 4, 15 tiles will wait and poll for 1s while the meta tile is rendered and sliced up.

Changing to a mutex would help

Test Plan

The output of a tile map request should be indentical whether served with meta tiling enabled or without.

Funding/Resources

TBD

Sandbox

​http://trac.osgeo.org/mapguide/browser/sandbox/rfc90