Cannot read properties of undefined (reading 'duration')

[victordidenko]

We have many errors in the Sentry, which looks like this

{
message: Cannot read properties of undefined (reading 'duration'),
name: TypeError,
stack: 
TypeError: Cannot read properties of undefined (reading 'duration')
    at Tf (.../player.js:188:3879)
    at CD.getExpiredTime (.../player.js:218:3581)
    at WD.stuckAtPlaylistEnd_ (.../player.js:218:45386)
    at kh.<anonymous> (.../player.js:218:37265)
    at i.dispatcher.i.dispatcher (.../player.js:23:40858)
    at Qh (.../player.js:23:41677)
    at kh.trigger (.../player.js:23:43393)
    at kh.haveMetadata (.../player.js:188:17321)
    at .../player.js:188:15997
    at Z_ (.../player.js:188:25260)
}

Unfortunately I cannot say conditions for this issue, I've never seen it in dev environment, but it is very frequent (in fact, this is the most repeating error in our Sentry), but from minified code I figured that this is sumDurations function:

http-streaming/src/playlist.js

Line 320 in fef62d9

durations += durationList[i].duration;

Maybe it is possible to add some kind of a guard here, at least?
Like

durations += durationList[i]?.duration ?? 0;

[adrums86]

Do you have an example manifest we could create a reduced test case with? I think we need a little more information to determine what is causing the durationList to be undefined in this case

[victordidenko]

I will try to find stream, but this may be happen in some circumstances, which are not fully depend on a stream... Unfortunately, Sentry logs from production doesn't show full image, and as I say, I've never seen this error in development environment.

But what could be wrong in adding nullish guard?

[adrums86]

Simply trying to understand why this is happening in your environment and not more common elsewhere. Nothing wrong with a nullish guard, feel free to submit a PR. However a quick look at the code suggests there might be a bigger problem with the media if the durationList is undefined. Meaning a nullish guard might only push the problem further down stream. The durationList is generated from the reduce output from the media playlist. See: playlist.js.

[victordidenko]

The issue is that we provide software for an external company, and do not own streams. I'll ask our QA engineers, if they have access to the client's production server.

Meanwhile, in the Sentry I saw different stacktrace with the similar error:

{
message: Cannot read properties of undefined (reading 'duration'),
name: TypeError,
stack: 
TypeError: Cannot read properties of undefined (reading 'duration')
    at AE.calculateBaseTime_ (.../player.js:218:343)
    at AE.update (.../player.js:215:7438)
    at n0.playlist (.../player.js:203:56263)
    at WD.handleUpdatedMediaPlaylist (.../player.js:218:38102)
    at Ch.<anonymous> (.../player.js:218:36246)
    at i.dispatcher.i.dispatcher (.../player.js:23:40858)
    at Jh (.../player.js:23:41677)
    at Ch.trigger (.../player.js:23:43393)
    at Ch.haveMetadata (.../player.js:188:17546)
    at .../player.js:188:15997
}

This looks like this place:

http-streaming/src/util/media-sequence-sync.js

Line 253 in fef62d9

baseTime -= segment.duration;