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https://issues.apache.org/jira/browse/COUCHDB-2052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13894405#comment-13894405
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Benoit Chesneau commented on COUCHDB-2052:
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rather than API discovery I would prefer to describe capabilities.
If we take the example of the replication for example, it seems that couchlite
can use _bulk_get on the couchbase sync gateway or _changes and other things on
couchdb. But some servers like the coming release of rcouch can handle both (ie
proposing the _bulk_get feature).
In the smpt world it would be represented as 2 capabilities corresponding to 2
well defined api/protocols. Here why not something like REPCOUCHDB01 and
REPCOUCHBASE01 . whatever. A capability would then describe a behaviour and an
entry point depending on the transport (http by default). Describing an
expected behaviour is a way easier imo than expecting that all applications are
able to parse a message in time etc. Also it would allows to define a default
behaviour eventually.
Then we could have a behaviour/protocol per type of actions:
- Document api
- Replication
...
In term of implementation, when using the HTTP protocol why not getting them by
issuing an OPTIONS method to / ?
> 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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