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From "Benoit Chesneau (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-2052) Add API for discovering feature availability
Date Fri, 07 Feb 2014 15:34:20 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-2052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13894629#comment-13894629
] 

Benoit Chesneau commented on COUCHDB-2052:
------------------------------------------

[~snej] afaik definiing entrypoint and their use or not is about protocol. Saying I can use
_bulk_get is a capability. defining it is available for the replication is a protocol. 

About using Options, well this what we already use for CORS which far more than checking available
methods.

[~bigbluehat] Hypermedia is fine, but a little to much oriented URI. I wonder how it could
work on non HTTP protocols. 

About channels and co, I am afraid we are  mixing 2 issues, ie metadata added by channels,
and defined by the channel spec or protocol, and the way we want to advertise the capabilities
of a node.  

In fact I am thinking that this story of "API" is misleading, I would prefer to speak about
resources and the capabilities of a node to accept them or not (REST).  URI are a way to see
these resources but not only. Concretely a Couchdb node actually exposes the following resources

database
document
replication
stat
...

on which you can access over http, can bulk get ...



- benoit



> Add API for discovering feature availability
> --------------------------------------------
>
>                 Key: COUCHDB-2052
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-2052
>             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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