[fusion-trac] #137: Support multiple hosts for tile maps
Fusion
trac_fusion at osgeo.org
Wed Oct 8 15:23:11 EDT 2008
#137: Support multiple hosts for tile maps
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Reporter: jbirch | Owner: madair
Type: enhancement | Status: new
Priority: P2 | Milestone: 2.0
Component: Widgets | Version: SVN
Severity: Major | Keywords:
External_id: | State: New
Browser: All | Os: All
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One of the limiting factors of perceived performance for tiled maps is
that (by RFC) the number of active HTTP 1.1 connections to a server should
be limited to 2. This providers a very small pipeline for service
multiple images, javascript files, and other supporting resources.
!OpenLayers works around this by allowing you to specify multiple hosts to
retrieve tiles from as a comma-separated list, and accesses them in a
round-robin fashion. This could either be used to make requests to
several load-balanced tile servers, or a single server with multiple DNS
host entries pointing to it.
To my understanding, Fusion currently requires that the user specify a
single !MapGuide !MapAgent or !MapServer CGI in its config file, and then
uses that for all requests of that type.
I am not sure what the implications of this would be (does !OpenLayers
also round-robin non-image requests?) but I believe that an ideal system
would use a single host from the list per-client for all non-map requests
so that you don't run into session problems, but would use a list of hosts
for tiled map requests.
One way of supporting this would be to leave the WebTierURL specification
in the config.json file alone (and use this for non-mapimage requests),
and add an extension to the Map element to specify which hosts to retrieve
maps from. Again, I'm not sure of how this would work with
Fusion/OpenLayers internals, but it seems like the least invasive
approach, and would also lend itself well to defining external sources for
non-!MapGuide/!MapServer map types.
--
Ticket URL: <http://trac.osgeo.org/fusion/ticket/137>
Fusion <http://trac.osgeo.org/fusion>
Fusion is a web-mapping application development framework for MapServer and MapGuide OS.
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