Hi William On Wed, Jul 12, 2017 at 8:29 AM, William Valencia <[email protected]> wrote: > I noticed something weird with QGIS. So when making an "Add WCS Layer" > request with QGIS, I noticed that (After initial GetCapabilities and > DescribeCoverage), multiple redundant calls to my WCS Server are made. The > actual "Add" Button makes 12 calls to my WCS Server. It calls 1 > GetCapabilities, 1 DescribeCoverage, 4 GetCoverage and then repeats the last > 6 calls for a total of 12 calls. I am unsure why QGIS makes 4 GetCoverage > calls in the first place, let alone the repeated last 6 calls for the total > of 12 calls. Anyone know why QGIS is doing this?
I am not the author of the WCS provider, but I have some leads... the extra GetCoverage calls are used for detection of some server behaviors, from the code comments it looks like at some point there were incompatibilities among WCS server implementations that lead to addition of these checks to work around the incompatibilities. Not sure if these checks are still necessary with the current versions of map servers. For the repeated calls, this a side-effect of introduction of multi-threaded rendering since QGIS 2.4. WCS provider get cloned for use in worker thread, but the cloning is sub-optimal - it does not pass the downloaded capabilities, so cloned provider has to fetch that again. It should not be hard to fix (I have fixed that for WMS in the initial work, but WCS provider had low priority at the time). Regards Martin _______________________________________________ QGIS-Developer mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
