getStats on "closed" objects

[aboba]

From Philipp Hancke:

7. page 6, section 2.3.2

Stops and closes the DTLS transport object. Since stop() is final, if
start() is called afterwards, throw an InvalidStateError exception.

what happens when calling getStats after this? There was some discussion of that case for the PC -- see w3c/webrtc-stats#3 and https://bugzilla.mozilla.org/show_bug.cgi?id=1056433 for some implementation rationale.

[robin-raymond]

getStats returns a promise, so (to me) the promise should return but trigger the failed state... ?

[robin-raymond]

Or it returns last state...

[aboba]

The May ORTC Editor's draft says the following:

"For RTCDtlsTransport.getStats(), check whether RTCDtlsTransport.start() has been called; if not, reject p with an InvalidStateError. For RTCIceTransport.getStats(), check whether RTCIceTransport.start() has been called; if not, or if RTCIceTransport.stop() has been called, if not, reject p with an InvalidStateError. For RTCRtpSender.getStats(), check whether RTCRtpSender.send(parameters) has been called; if not, if not, reject p with an InvalidStateError. For RTCRtpReceiver.getStats(), check whether RTCRtpReceiver.receive(parameters) has been called; if not, if not, reject p with an InvalidStateError."

[BA] I don't understand why these error conditions are needed. If an object has not yet been configured to send or receive data, can't the stats returned reflect this (e.g. octets sent/received = 0)? Similarly, if the object has been closed, why can't the stats reflect the last stats prior to the closure?

An alternative that would be compatible with the proposed WebRTC 1.0 PR:

getStats
Gathers stats for the given object and reports the result asynchronously. If the object has not yet begun to send or receive data, the returned stats will reflect this. If the object is in the closed state, the returned stats will reflect the stats at the time the object transitioned to the closed state.

When the getStats() method is invoked, the user agent must queue a task to run the following steps:

Let p be a new promise.

Return, but continue the following steps in the background.

Start gathering the stats.

When the relevant stats have been gathered, return a new RTCStatsReport object, representing the gathered stats.

No parameters.
Return type: Promise