Hi Dave,
the callback in question extends the official OGC conditional capabilties
request (based on the
update sequence number) to non compliant clients that can do HTTP
conditional requests instead.
So the answer would be, "if something changes, you'd have to increment the
update sequence,
since your caps document changed".
However, I understand and agree this is indeed a problem, the capabilities
document can change
due to dimensions, but also due to security, without anything touching the
GeoServer configuration (which
would bump the update sequence).
As a quick fix, there is already a CAPABILITIES_CACHE_CONTROL_ENABLED
envvar/sysvar/servlet context variable
that can be set to false to disable the callback.
As a longer term fix, the callback should probably be modified to identify
elements making the caps
dynamic. Like, for example, scan the layers available to the current user
and create a digest out of them
(fixes security) and if during the scan any has dimensions, uh, probably
disable the conditional request fully.
On the background, there is still the issue of proper OGC clients making
update sequence based conditional
request, those will still fail to notice something has changed... this
mapserver ticket has enough information
about it without you needing to read the OWS specifications:
https://trac.osgeo.org/mapserver/ticket/2384
Hum... from what I read, the "etag" computed above could also be used for
conditional negotiation at the OGC
level.
Cheers
Andrea
On Fri, Mar 31, 2017 at 8:06 PM, Dave Blasby <[email protected]>
wrote:
> Hi,
>
> I noticed that the GetCap document was not up-to-date. When I dug into
> it, I found that CapabilitiesCacheHeadersCallback was returning a 304
> (i.e. no changes).
>
> However, this is a timeseries dataset (ie. Time Dimension tab on Layer
> Publish).
>
> (i.e. a GeoGIG or PostGIS dataset with a time column)
>
> The issue is that the dataset is changing. A new Time value is inserted
> into the dataset - the getcap (set to LIST) should show this new value.
> However, the document is cached because the catalog hasn't detected any
> changes.
>
> We talked about this earlier ("Time dimension on Vector Layer is SLOW")
> and decided that caching this information is inappropriate (and I agree)
> for this reason.
>
> What should be done about this?
>
> Thanks,
> Dave
>
>
>
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