Hi Jody, that is pretty good for documentation, but it presumes we can enumerate all possible cases in advance. I don't feel like I have a powerful enough crystal ball.
Cheers Andrea On Tue, May 25, 2021 at 8:51 PM Jody Garnett <[email protected]> wrote: > Sorry I did not have anything to add earlier. > > To expand on the meeting discussion, the UI could be presented in terms of > desired effect. > > *Cache Control Handling for WMS Dimension Matching* > Configure cache-control header when matching latest, nearest match, and > empty images generated with a warning header: > * ( ) Static dataset: cache latest, nearest match, and empty > * ( ) Additive dataset: do not cache latest tiles, continue to cache > nearest match and empty > * ( ) Dynamic dataset: do not cache latest, cache nearest match, and empty > > -- > Jody Garnett > > > On Fri, 21 May 2021 at 03:35, Andrea Aime <[email protected]> > wrote: > >> Hi all, >> WMS time handling (and in general, dimension handling) can have a fair >> bit of "magic" going on: >> >> - When no time is provided, a default time value is set (but the >> actual value can change over time) >> - When time is provided but it's not a match, a nearest match >> behavior can be configured, returning a different time >> - When nearest time is enabled, a max distance can be configured, >> which might make the lookup fail and return an empty tile regardless >> >> Abiding to the spec, GeoServer sets a HTTP header, a WARNING, in >> responses talking about the actual time being used (or the lack of match). >> Which is great for strictly compliant WMS servers that bothered to handle >> this aspect for the spec... but I don't know of any that actually do LOL. >> >> If the dataset is strictly static it's maybe not a big of a deal, as the >> response to a given URL is going to be mostly static (there might be >> redundant caching). >> But if the time based dataset is dynamic, with continuous ingestion of >> new data, then we have a problem. >> >> Generally speaking, this is problematic for web clients and anything in >> between (proxies, edge servers) that might decide to cache the response >> in front of the eventual WMS/WMTS (in other words, the issue goes beyond >> what we might control at the integrated GWC level. >> >> In these cases, the important bit is to give whatever is in front the >> information about whether the tile is not cacheable or not, >> while maybe avoid trying to cache a blank tile locally, or a tile with >> the wrong content (in dynamic situations, a possible missing time >> in a time series could also be filled later). >> >> However... someone could be happy with the status-quo, especially when >> dealing with static datasets (historical ones, not active). >> >> So... we think a good way to handle this is to add the following settings >> to caching defaults, and per layer settings, allowing >> to disable caching for situations that would cause warnings, letting the >> admin decide what to do: >> [image: image.png] >> In addition to not caching the tiles, the response headers would have a >> clear indication that the response is not meant to >> be cached, in other words: >> >> Cache-Control: no-cache, no-store, must-revalidate >> Pragma: no-cache >> Expires: 0 >> >> This should hopefully work across the board. >> >> Cheers >> Andrea >> >> == GeoServer Professional Services from the experts! Visit >> http://goo.gl/it488V for more information. == Ing. Andrea Aime @geowolf >> Technical Lead GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa >> (LU) phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 >> http://www.geo-solutions.it http://twitter.com/geosolutions_it >> ------------------------------------------------------- *Con riferimento >> alla normativa sul trattamento dei dati personali (Reg. UE 2016/679 - >> Regolamento generale sulla protezione dei dati “GDPR”), si precisa che ogni >> circostanza inerente alla presente email (il suo contenuto, gli eventuali >> allegati, etc.) è un dato la cui conoscenza è riservata al/i solo/i >> destinatario/i indicati dallo scrivente. Se il messaggio Le è giunto per >> errore, è tenuta/o a cancellarlo, ogni altra operazione è illecita. Le >> sarei comunque grato se potesse darmene notizia. This email is intended >> only for the person or entity to which it is addressed and may contain >> information that is privileged, confidential or otherwise protected from >> disclosure. We remind that - as provided by European Regulation 2016/679 >> “GDPR” - copying, dissemination or use of this e-mail or the information >> herein by anyone other than the intended recipient is prohibited. If you >> have received this email by mistake, please notify us immediately by >> telephone or e-mail.* >> _______________________________________________ >> Geoserver-devel mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/geoserver-devel >> > -- Regards, Andrea Aime == GeoServer Professional Services from the experts! Visit http://goo.gl/it488V for more information. == Ing. Andrea Aime @geowolf Technical Lead GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa (LU) phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 http://www.geo-solutions.it http://twitter.com/geosolutions_it ------------------------------------------------------- *Con riferimento alla normativa sul trattamento dei dati personali (Reg. UE 2016/679 - Regolamento generale sulla protezione dei dati “GDPR”), si precisa che ogni circostanza inerente alla presente email (il suo contenuto, gli eventuali allegati, etc.) è un dato la cui conoscenza è riservata al/i solo/i destinatario/i indicati dallo scrivente. Se il messaggio Le è giunto per errore, è tenuta/o a cancellarlo, ogni altra operazione è illecita. Le sarei comunque grato se potesse darmene notizia. This email is intended only for the person or entity to which it is addressed and may contain information that is privileged, confidential or otherwise protected from disclosure. We remind that - as provided by European Regulation 2016/679 “GDPR” - copying, dissemination or use of this e-mail or the information herein by anyone other than the intended recipient is prohibited. If you have received this email by mistake, please notify us immediately by telephone or e-mail.*
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