[mapserver-users] mamcache vertical assembly

Wed Feb 6 06:03:48 PST 2019

Steve,

Thanks for the detailed explanation. Sounds like a very logical solution.
MapServer is so powerful in its ability to both consume and serv WMS.

The thread caught my eye because my apps typically have a few dozen layers
that users can turn on/off in any combination, which makes caching less
practical.

Best regards,
Rich

On Tue, Feb 5, 2019 at 8:49 PM Stephen Woodbridge <
stephenwoodbridge37 at gmail.com> wrote:

> 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
> > <stephenwoodbridge37 at gmail.com <mailto:stephenwoodbridge37 at gmail.com>>
> > 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)
> >     <steve.lime at state.mn.us <mailto:steve.lime at state.mn.us>> wrote:
> >
> >>     I’ll try to derive something from the source and report back.
> >>
>  ------------------------------------------------------------------------
> >>     *From:* mapserver-users <mapserver-users-bounces at lists.osgeo.org
> >>     <mailto:mapserver-users-bounces at lists.osgeo.org>> on behalf of
> >>     Stephen Woodbridge <stephenwoodbridge37 at gmail.com
> >>     <mailto:stephenwoodbridge37 at gmail.com>>
> >>     *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
> >>
> >>     ---
> >>     This email has been checked for viruses by Avast antivirus software.
> >>     https://www.avast.com/antivirus
> >>
> >>     _______________________________________________
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> >     _______________________________________________
> >     mapserver-users mailing list
> >     mapserver-users at lists.osgeo.org
> >     <mailto:mapserver-users at lists.osgeo.org>
> >     https://lists.osgeo.org/mailman/listinfo/mapserver-users
> >
> >
> >
> > --
> > Richard W. Greenwood, PLS
> > www.greenwoodmap.com <http://www.greenwoodmap.com>
>
>

-- 
Richard W. Greenwood, PLS
www.greenwoodmap.com
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