[mapserver-users] Dynamically update layers without service interruption

[Stephen Woodbridge]

The key to this is to minimize the time that the data and mapfile are 
potententially out of sync or the time a file might be being updated so 
that it is in a state of flux that might cause an error if a request 
tries to read the file while it is being updated.

I have managed this in the past with parallel data trees and a symbolic 
link on Linux.

/path/to/data/
/path/to/data/imagesA
/path/to/data/imagesB
/path/to/data/images -> imagesA or imagesB

the map file points to /path/to/data/images and that is a symbolic link 
to either imagesA or imagesB, for example lets say imagesA

So the update process would be something like:

# sync your A and B trees
rsync -s imagesA/* imagesB/.

# update the images in imagesB and the mapfile in imagesB

# make imagesB live
(cd /path/to/data/; rm images; ln -s imagesB images)

# if you want to rollback to imagesA
(cd /path/to/data/; rm images; ln -s imagesA images)

Hope this helps,
   -Steve W

Dan Little wrote:
> Yes, it's a matter of how you do your data management.
> 
> Generally, if you're using MapServer in CGI mode you can update the
> data, or the mapfile, and the next time a request comes in, it will
> see the updated version of your image.
> 
> 
> 
> ----- Original Message ----
>> From: Björn Harrtell <bjorn.harrtell at gmail.com> To:
>> mapserver-users at lists.osgeo.org Sent: Mon, December 7, 2009 3:11:36
>> PM Subject: [mapserver-users] Dynamically update layers without
>> service interruption
>> 
>> Is it possible to dynamically add and/or update layer definitions
>> that also might involve updates to the underlying data without
>> *any* service interruption? I'm primarily interested in this use
>> case when using raster layers.
>> 
>> I have indications that service interruptions can happen but cannot
>>  verify yet. I found 
>> http://www.mapserver.org/development/rfc/ms-rfc-44.html#rfc44 
>> describing the feature of dynamic updates (I assume?) but no
>> mention about if service interruption can be expected and/or how to
>> avoid it.
>> 
>> Regards,
>> 
>> Björn Harrtell _______________________________________________ 
>> mapserver-users mailing list mapserver-users at lists.osgeo.org 
>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
> 
> 
> 
> 
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