Skipping layers that fail to load

[iansan]

Currently if a map file contains layers that make database connections and the database is down, a map will never successfully complete.

This is a request for an option at the map and/or layer level to gracefully skip layers that fail to load so that a map can still be generated.

[dmorissette]

The CONFIG “ON_MISSING_DATA” “[ACTION]” option was added in RFC-47:

http://mapserver.org/development/rfc/ms-rfc-47.html

I guess it should be extended to work with db connections if that's not the case already.

[aboudreault]

I'm going to extend the ON_MISSING_DATA behavior to support this case. I can make the ms*LayerOpen() functions of oracle, mysql and postgis return MS_DONE if the process is terminated for the layer and handle that return code everytime we call msLayerOpen().

[aboudreault]

The MS_DONE code will be handled only for the layers of type POSTGIS, ORACLESPATIAL and MYSQL.

[aboudreault]

I think this ticket would need a RFC to document the changes. To support the requested feature, the behavior of the msLayerOpen function has to be changed. The new behavior of the function would be that it can return MS_DONE, which has the meaning that the appropriate ms*LayerOpen call fails but the map uses ON_MISSING_DATA IGNORE.

This new return code will have to be handled by the different request types: mode map,nquery and all requests of wms/wfs/etc.. to support properly the ON_MISSING_DATA action.

Steve, Paul, Daniel, I would like to get your opinion on that feature before writing a small RFC.