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From "Benjamin Young (JIRA)" <>
Subject [jira] [Commented] (COUCHDB-2052) Add API for discovering feature availability
Date Fri, 07 Feb 2014 15:46:21 GMT


Benjamin Young commented on COUCHDB-2052:

[~benoitc] by using URI (and not URL) in your comment above, you prove the point. :) URI's
are just identifiers. They can be relative, absolute, and even non-dereferencable (if you
want to go there...).

To your point about protocols. It can be a tangled word. CouchDB (et al) use HTTP for their
protocol. Anything we do inside or on top of that could be considered a protocol as well,
but that starts to tangle things up a bit.

We'll be best served if we "cut with the grain" of the web and use the pieces as they were
designed: URI's, HTTP methods, media types, etc.

Feature and capability aren't new territory. We'd be best served by "rinsing and repeating"
some proven method of scalable resource the Web. :)

> Add API for discovering feature availability
> --------------------------------------------
>                 Key: COUCHDB-2052
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>      Security Level: public(Regular issues) 
>          Components: HTTP Interface
>            Reporter: Jens Alfke
> I propose adding to the response of "GET /" a property called "features" or "extensions"
whose value is an array of strings, each string being an agreed-upon identifier of a specific
optional feature. For example:
> 	{"couchdb": "welcome", "features": ["_bulk_get", "persona"]}, "vendor": …
> Rationale:
> Features are being added to CouchDB over time, plug-ins may add features, and there are
compatible servers that may have nonstandard features (like _bulk_get). But there isn't a
clear way for a client (which might be another server's replicator) to determine what features
a server has. Currently a client looking at the response of a GET / has to figure out what
server and version thereof it's talking to, and then has to consult hardcoded knowledge that
version X of server Y supports feature Z.
> (True, you can often get away without needing to check, by assuming a feature exists
but falling back to standard behavior if you get an error. But not all features may be so
easy to detect — the behavior of an unaware server might be to ignore the feature and do
the wrong thing, rather than returning an error — and anyway this adds extra round-trips
that slow down the operation.)

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