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.*
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