nci/gsky

`502 Server Error: Bad Gateway` when requesting 'large' bbox

Closed this issue · 3 comments

khornlund commented

GetCoverage requests for landsat8_nbar_16day cause an error for certain bbox values.

Here is an example of a working request using (**134.00**, -37.00, 141.00, -35.00):

http://gsky.nci.org.au/ows/dea?version=1.0.0&request=GetCoverage&service=WCS&Coverage=landsat8_nbar_16day&BBox=134.0%2C-37.0%2C141.0%2C-35.0&time=2017-12-27T00%3A00%3A00.000Z&crs=EPSG%3A4326&format=GeoTIFF&width=2556&height=2570&Styles=fc

And a broken request using (**133.00**, -37.00, 141.00, -35.00):

http://gsky.nci.org.au/ows/dea?version=1.0.0&request=GetCoverage&service=WCS&Coverage=landsat8_nbar_16day&BBox=133.0%2C-37.0%2C141.0%2C-35.0&time=2017-12-27T00%3A00%3A00.000Z&crs=EPSG%3A4326&format=GeoTIFF&width=2556&height=2570&Styles=fc

Perhaps it can't handle boxes over a particular size?

Kind Regards,
Karl

edisonguo commented

The requested width and height are limited to 512 per request. If either exceeds 512, you get the Bad Gateway error (not very friendly I know). If you want to request large bbox, please subdivide it into multiple requests. We need to put certain limits on the production service to constraint resource usage.

khornlund commented

I'm using width=2556&height=2570 in the query, so does that mean the restriction applies to the number of pixels selected in the original data? If so, it will be quite hard for users to know the maximum size of the area they can request.

Are there different limits for the different layers/endpoints? I've used this resolution/bbox successfully for MODIS Vegetation Fractional Cover 8-day v3.1.

edisonguo commented

The restriction is applied to the width and height parameters to limit the number of pixels selected in the original data. In resource usage terms, these are essentially the memory and cpu consumption. To my knowledge, for large datasets such as landsat and sentinel2, width and height are capped at 512. For smaller datasets such as Geoglam, the restrictions are lifted to much higher numbers. However, I don't know the exact numbers. Ultimately these restrictions are set by the ops team as they manage the production deployment of gsky.