RTP NACK responder buffers not released after RemoveTrack/Stop (while PC still alive)

[ivanlukomskiy]

Your environment.

• Version: pion/interceptor v0.1.44; pion/webrtc v4.2.1
• Go version: 1.25.5
• Browser: any (it's a server-side issue)

Hi!

I use Pion in large-scale production. The app is video-only streaming from server to clients. Within a single connection users can subscribe and unsubscribe from video streams. There are hundreds of connections per pod and dozens of streams per connection.

It works great, but i got issues with large gradual growth of memory usage (several GB).

After profiling, i found out that the most of memory is occupied by NACK buffers of stopped streams.

If PC is closed, memory frees up, but in our setup we heavily reuse connections.

What did you do?

We enable NACK and RTCP interceptors like this:

webrtc.ConfigureNack(mediaEngine, interceptorRegistry)
webrtc.ConfigureRTCPReports(interceptorRegistry)
webrtc.ConfigureTWCCSender(mediaEngine, interceptorRegistry)

Streams are dynamically added/removed:

track, err := webrtc.NewTrackLocalStaticRTP(...)
transceiver, err := conn.AddTransceiverFromTrack(track, ...)
rtpSender := transceiver.Sender()

// later:
conn.RemoveTrack(rtpSender)
transceiver.Stop()
rtpSender.Stop()

Heap profiling (pprof, inuse_objects and inuse_space) shows the majority of memory retained in:

github.com/pion/interceptor/internal/rtpbuffer.(*PacketFactoryCopy).NewPacket
github.com/pion/interceptor/internal/rtpbuffer.NewPacketFactoryCopy.func2

What did you expect?

Removed tracks won't occupy large chunks of memory

What happened?

They do

[ivanlukomskiy]

I opened a PR that fixes resources cleanup:
#405