Well capababilities idea come from the SMTP world at first but same idea. That's indeed a good idea. Identification per see would't be efficient on a client level. We don't really want to reproduce the nightmare we have with the browsers with different U/A. Testing capabilities is definitely a good way to test what an endpoint support. For example some endpoint or node could only support the replication. one ather could support the couchdb/1.3 api. other could offers some extensions or plugin like you say.
Though In these days I would modernize it a little as a way to describe the api endpoints with the resource supported. We could base it on the host metadata rfc [1] or using some new stuffs like the JSON api [2] . [1] http://tools.ietf.org/html/rfc6415 [2] http://jsonapi.org/ Maybe there are other specs around. Anyway it also means we need to describe our API accurately and what we support so expectation are guaranteed. So if i noow that this server is couchdb 1.1 compatible i don't have to test the vendor, like I now have to do in couchdbkit or couchbeam to handle cloudant and couchdb nodes for small changes. Instead I could just lod the capabilities and make sure to make them available at the client level. We could also make a compatibility grid later for the users based on capabilities. - benoit On Wed, Jun 5, 2013 at 12:40 AM, Joan Touzet <[email protected]> wrote: > Today, if I GET http://localhost:5984/ , I get: > > > {"couchdb":"Welcome","uuid":"b1b1dbe964914a9cb1467bfd4f297fed","version":"1.3.0","vendor":{"version":"1.3.0","name":"The > Apache Software Foundation"}} > > If I GET from http://mozauto.iriscouch.com/ , I get: > > > {"couchdb":"Welcome","uuid":"bac168113808f7ed357fb53f3a7a68bc","version":"1.3.0","vendor":{"version":"1.3.0r1","name":"Iris > Couch"}} > > And if I GET http://wohali.cloudant.com/ , I get: > > {"couchdb":"Welcome","version":"1.0.2","cloudant_build":"1202"} > > I believe I get further still different responses from Pouch and Touch > and other CouchDB-alikes, provided they even have an equivalent of > GET /. > > Long ago, in a galaxy far far away, the developers of Internet Relay > Chat daemons faced a similar problem. While they were bound by a single > RFC (and later, its twin), each developer wanted to extend the program > in interesting and unique ways. Some of those features became > commonplace and built a shared understanding, others were unique > capabilities of specific implementations, and yet others indicated > specific incompatibilities introduced for nefarious purposes. > > While the sordid history of the IRC protocol is a topic for drinks after > a meetup some night, one lesson learned has proved exceedingly useful: > the CAPAB string. Documented in the TS6 specification[1] but universally > adopted, server-to-server CAPAB/PROTOCTL provided a negotiation of both > implemented functionality as well as services offered. A further > extension was created for client-to-server capabiliity negotiation > as a draft RFC[2][4] and is also widely implemented. > > To make this more tangible, reference this list[3] of IRC server > CAPABilities. If you've ever used IRC, and especially different IRC > networks, you should be able to intuitively understand how this up-front > negotiation helps simplify server-to-server connection negotiation. > > --- > > I think CouchDB should extend its identification in the root-level > document with a capability advertisement. This would help prevent the > current anti-patterns in production use of CouchDB: > > 1. Client library negotiation based exclusively on "compatibility > with >= version of Apache CouchDB," which is nebulously documented > at best. > > 2. Provide a clear means by which CouchDB plugins and CouchDB-alike > services can advertise their availability. > > 3. Provide a way for alternate implementations of similar > functionality to indicate interoperability. > > 4. Possibly simplify the replicator (though this is a special case of > 1 and 2 above). > > I've gotten no further than this in my thinking yet; I didn't want to > start implementation before folks had a chance to say whether they > thought it'd be a good idea or not. > > [1]: > https://github.com/grawity/irc-docs/blob/master/server/ts6.txt#L205-L216 > [2]: https://tools.ietf.org/html/draft-mitchell-irc-capabilities-01 > [3]: https://github.com/grawity/irc-docs/blob/master/server/ts-capab.txt > [4]: https://github.com/grawity/irc-docs/tree/master/client/CAP-drafts > > -- > Joan Touzet | [email protected] | wohali everywhere else
