On 2/5/2019 8:52 PM, Richard Greenwood wrote:
Stephen,
I was watching this thread hoping for a reply to your original
question because it's an interesting problem. If you have time to
provide a more detailed explanation of your solution I'd be interested.
So what I had originally were 7 layers of NOAA ENC (Electronic Nautical
Charts) being pulled from the NOAA WMS service and these were getting
cached locally in mapcache. Since my app was always turning on/off all
seven layers as a set, I wanted to build a new layer that merged all
seven into a single layer. Part of the reason for this was to reduce the
number of layer in openlayers for performance improvements. This would
be just a vertical stacking of the the seven layers into one. Because of
the way NOAA service is structured each layer has a different end point
so it was not possible to have their server do the stacking.
I eventually found this post:
https://lists.osgeo.org/pipermail/mapserver-users/2012-April/072045.html
which suggests, this might no be the best approach.
In addition, while looking at this issue I realized the NOAA service
changed it layer definitions for some of the data and my mapcache stuff
was broken as a result. In the end, I decided to create a mapserver
mapfile that did WMS client requests to the NOAA server and broke up the
seven layers into 21 (7 each area, line and point) smaller layers that
allowed for more correct stacking of the data and setting appropriate
MIN/MAX scaledenom values as recommended by the getCapabilities for the
NOAA services. Now I have one mapcache layer that uses the new mosaic
mapfile and this does the vertical stacking which is slow given that
mapserver has to make about 21 WMS requests to serve each metatile
request from mapcache. But the end result is good and tiles are fast
once they are populated.
Also, I will note that the NOAA ENC service updates the chart data on a
regular basis, so I expire my tiles in the cache after 7 days so they
get regenerated possible using new data. I think because of this, the
strategy of using mapserver to do the stacking and mapcache to handle
the caching is a better division of labor and once the app is converted
to use the new mosaic layer, I'll remove the 7 old layers to free up
disk space.
Hope this helps someone with a similar issue.
Best regards,
-Steve W
Best regards,
Rich
On Tue, Feb 5, 2019 at 4:38 PM Stephen Woodbridge
<[email protected] <mailto:[email protected]>>
wrote:
I found response to question by Thomas on this subject that
suggested it might cause a deadlock if you ran out of connections.
Anyway I decided to build a new map file to do the vertical
assembly and then cache that through mapcache.
-Steve
Sent from my iPhone
On Jan 27, 2019, at 11:35 PM, Lime, Steve D (MNIT)
<[email protected] <mailto:[email protected]>> wrote:
I’ll try to derive something from the source and report back.
------------------------------------------------------------------------
*From:* mapserver-users <[email protected]
<mailto:[email protected]>> on behalf of
Stephen Woodbridge <[email protected]
<mailto:[email protected]>>
*Sent:* Sunday, January 27, 2019 7:08:38 PM
*To:* mapserver-users
*Subject:* [mapserver-users] mamcache vertical assembly
Hi,
The mapcache docs has a page for vertical assembly but it is blank :(
I have 7 layers in mapcache and I would like to vertically assemble
these into a composite layer. In the past I have been loading all
7 in
openlayers but it makes more sense to just composite them into a new
layer. There are some scale limits that apply to the various layers.
Does anyone have some info on how to do this in mapcache directly
rather
than create a mapfile and compositing them in mapserver and then
making
that a new layer in mapcache.
Thanks,
-Steve W
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--
Richard W. Greenwood, PLS
www.greenwoodmap.com <http://www.greenwoodmap.com>
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