[mapserver-users] Updating MapCache on feature edits

[Seth G]

Thanks Andreas for the OGR suggestion and clarification on 
ows_updatesequence.

There was a tantalising sentence in 
https://agile-online.org/Conference_Paper/CDs/agile_2012/proceedings/papers/Paper_Loechel_Caching_techniques_for_high-performance_Web_Map_Services_2012.pdf 
- with no space or links to the techniques to solve the problem!

" The purge effect leads to the problem, that a cache or mapserver might 
respond outdated maps. This is assumed to be critical in two cases:
1. Manually changing data: The map has to reflect the change 
immediately; otherwise users get confused and try to perform the change 
again.
2. Automatically changing data: public map layers with up to date 
information, like traffic conditions or weather data. There are special 
techniques to solve this problem, but these cannot be explained in 
detail here due to space limitations."

I'm rethinking the design of my application to workaround it, and can 
think of 3 possible options:

1. Cache higher zoom levels, and switch to dynamic WMS at higher scales 
as edits are normally made when zoomed in
2. The application has a log in function, so I could switch to dynamic 
for users with edit-rights, and use a cache for read-only users (which 
would update nightly). This would solve the issue where a user makes an 
edit and the layer doesn't change.
3. Try and edit the XML MapCache config file and update a dimension to 
cause a new cache to be generated following an edit. This approach would 
probably lead to race conditions, and would need to be reloaded in Apache.

Regards,

Seth

On 04/10/2016 15:44, Eichner, Andreas - SID wrote:
> Seth,
>
> you can use OGR to retrieve the updated features and give it to mapcache_seed.
> See http://mapserver.org/mapcache/seed.html#optional-commandline-options-when-using-ogr-geos .
>
> The ows_updatesequence metadata signals changes in the metadata returned by a GetCapabilities request, i.e. when adding/removing layers, descriptions and the like.
>
> HTH
>   
>> -----Ursprüngliche Nachricht-----
>> Von: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] Im
>> Auftrag von Seth G
>> Gesendet: Sonntag, 2. Oktober 2016 15:23
>> An: mapserver-users at lists.osgeo.org
>> Betreff: [mapserver-users] Updating MapCache on feature edits
>>
>> Hi list,
>>
>> I have a few MapServer layers based on data that can be edited at any
>> time. In practice this usually happens in short bursts every month or so.
>> The remaining time the layers would benefit greatly from using a tile
>> cache.
>>
>> Are there any suggested methods on how to automatically
>> purge/delete/change the cache when an edit happens when using MapServer
>> and Mapcache?
>>
>> I see that GeoWebCache/Geoserver allows a GeoRSS feed to invalidate
>> features
>> http://geowebcache.org/docs/current/configuration/layers/georss.html
>>
>>
>> The ows_updatesequence metadata parameter for a WMS layer looks like it
>> could be used somehow (see http://mapserver.org/ogc/wms_server.html#web-
>> object-metadata), but it seems that custom dimensions need to be requested
>> by the client, and any Mapcache configurations would need Apache to be
>> restarted.
>>
>> Any best practices, or solutions appreciated,
>>
>> Seth
>>
>>
>> --
>> web: http://geographika.co.uk <http://geographika.co.uk>
>> twitter: @geographika
>>
>>