Scaling WebRTC applications with Janus

1. Scaling server-side WebRTC applications: the Janus challenge Lorenzo Miniero @elminiero CommCon 2018 June 27th 2018, Wotton House, Surrey (UK)

2. Sorry Dan, pineapples on pizza = BIG NO

3. A picture of me as a kid for no reason Lorenzo Miniero • Ph.D @ UniNA • Chairman @ Meetecho • Open source believer Contacts and info • lorenzo@meetecho.com • https://twitter.com/elminiero • https://www.slideshare.net/LorenzoMiniero

4. 1. No, I don’t know what happened...

5. 2. Yes, Police is still looking for who stole my cheeks

6. Ok, let’s stop clowning around... Lorenzo Miniero • Ph.D @ UniNA • Chairman @ Meetecho • Open source believer Contacts and info • lorenzo@meetecho.com • https://twitter.com/elminiero • https://www.slideshare.net/LorenzoMiniero

7. What is Janus? Janus General purpose, open source WebRTC server • https://github.com/meetecho/janus-gateway • Demos and documentation: https://janus.conf.meetecho.com • Community: https://groups.google.com/forum/#!forum/meetecho-janus

8. Modular architecture • The core only implements the WebRTC stack • JSEP/SDP, ICE, DTLS-SRTP, Data Channels, ... • Plugins expose Janus API over different “transports” • Currently HTTP / WebSockets / RabbitMQ / Unix Sockets / MQTT / Nanomsg • “Application” logic implemented in plugins too • Users attach to plugins via the Janus core • The core handles the WebRTC stuff • Plugins route/manipulate the media/data • Plugins can be combined on client side as “bricks” • Video SFU, Audio MCU, SIP gatewaying, broadcasting, etc.

12. Extensible Architecture and API

13. Extensible Architecture and API

14. A quick look at plugins: SIP gateway

15. A quick look at plugins: RTP rebroadcaster

16. A quick look at plugins: Audio MCU

17. A quick look at plugins: Video SFU

18. The ﬁrst step towards scaling: benchmarking • Measuring Janus performance is not trivial... • Different plugins have different behaviours • Different technologies have different impact • Need to focus on individual features • SIP Gateway (SIP plugin) • Multimedia streaming (Streaming plugin) • Audio mixing (AudioBridge plugin) • Video routing (VideoRoom plugin) • ... What about the results?1 • When just relaying, bandwidth is typically the real bottleneck • Linear vs. exponential resource increase depends on plugin and topologies 1 https://janus.conf.meetecho.com/citeus

21. Beyond a single Janus instance: different strategies • Once performance is evaluated, other aspects come into play • Does a user stream need to stay within the plugin? • Can it be sent to/received from somewhere else? • Will this affect other connections? • How much is the context important? • What level of orchestration is needed? • All those questions can lead to different answers/solutions, e.g. 1 Plain load balancing 2 Media resource brokering (MRB) 3 Sharing the “burden” 4 Cascaded delivery 5 ...

22. Beyond a single Janus instance: different strategies • Once performance is evaluated, other aspects come into play • Does a user stream need to stay within the plugin? • Can it be sent to/received from somewhere else? • Will this affect other connections? • How much is the context important? • What level of orchestration is needed? • All those questions can lead to different answers/solutions, e.g. 1 Plain load balancing 2 Media resource brokering (MRB) 3 Sharing the “burden” 4 Cascaded delivery 5 ...

23. Plain load balancing • The simplest strategy of them all • You have N Janus instances available • You allocate users on one according to some logic • No orchestration needed, just knowledge of Janus addresses • User has list vs. HAProxy vs. nginx vs. ... • Logic can differ depending on the application • Pick a random server? • Use round robin? • Pick the one closest to the user? • Pick the least loaded? • Something else and/or any combination of the above?

26. Plain load balancing examples

29. Plain load balancing limitations • The only safe option is the SIP plugin • All streams are independent of each other • Even those that are related, are related via the SIP infrastructure • It might work with the Streaming plugin... • ... as long as you make sure the same mountpoints exist on all servers... • ... and they’re all fed with the same data! • With other plugins (e.g., AudioBridge or VideoRoom), it’s not as simple • Users meant for the same room may end up on different servers • ... unless the balancing component is aware of the context (“room”) • What about hosting the same room on different servers? • May work, but is also messy • Different contexts, multiple signalling channels, events overhead

34. Media resource brokering • A step above Plain load balancing • You have N Janus instances available • You allocate users based on logic AND context • Orchestration needed, here • You need to know which Janus instances are available... • ... and which one is doing what • Logic will differ depending on the context • Before allocating users, you allocate the context itself (e.g., a conference room) • Users are then sent wherever their context belongs to • Unlike Plain load balancing, can be used for everything • You just need to implement context awareness somehow, and track resources

38. Media resource brokering use case • Will work nicely with all plugins, if you manage the context • Context may give more info to SIP balancing logic • Conference rooms and Streaming mountpoints can be associated to instances • Broadcasting with Streaming plugin... • ... if MRB knows Janus X hosts mountpoint Y, it can send users there • Conference rooms with AudioBridge and/or VideoRoom... • New rooms can be “deployed” on a speciﬁc instance • Attempts to join room Y can be sent to Janus instance responsible for it • Won’t help much when the same resource needs to be scaled, though • e.g., many small rooms vs. one very large room • For that, some different approach is needed

42. Media resource brokering examples

46. Sharing the “burden” • A bit different from Brokering described before • You have N Janus instances available • You use one or more of them to serve the same context • Again, orchestration needed here too • You need to know which Janus instances are available... • ... and which one is serving which “subset” of the resource • Logic will differ depending on the resource • You identify how you can “split” the resource (unrelated parts) • Users are then sent where the resource “subset” is allocated • Less ﬂexible than Balancing and Brokering, and more speciﬁc • Can greatly help optimize delivery scenarios, though, depending on the context

50. Sharing the “burden” use case • A typical use case is larger conferences • Many active participants, with many viewers • The ﬁrst step is identifying the resources, and how they’re related • Publishers will send media: they don’t “depend” on each other • Subscribers only receive media: they depend on a speciﬁc publisher • Publishers can be the “subset”, here • A large conference room becomes N 1-to-many smaller broadcasts • Each publisher→subscribers distribution is allocated separately • Controlling application makes sure that viewer picks streams from the right place • Bob from Janus1, Alice from Janus2, Tom from Janus3, Jim from Janus2, ...

54. Sharing the “burden” example

59. RTP forwarding • All strategies so far assume related streams stay together • In smaller rooms, publishers and subscribers are all on the same server • In larger rooms, only the publisher and its subscribers are on the same server • No scenario where this relationship is broken • Apart from SIP and Streaming, but those are different (legacy interop) • How can streams from different servers interact? • Janus plugins don’t talk to each other... • ... and neither do different Janus instances! RTP forwarding A way to relay RTP behind the curtains, without WebRTC • e.g., relay VideoRoom publisher’s media to a Streaming mountpoint

63. RTP forwarding example

64. RTP forwarding example

65. While “plain” RTP, and not WebRTC? • Why not use WebRTC to “move” media around? • WebRTC uses RTP too, after all, and has a lot of useful stuff • Orchestrated properly, you can have one Janus see another Janus as a WebRTC user • Many reasons why we went for “plain” RTP, actually 1 Recipient may not be WebRTC compliant (e.g., FFmpeg script) 2 A lot of existing tools support RTP (and other things) natively 3 You may not need an encrypted stream (although RTP forwarders can do SRTP) 4 You may need to “feed” many recipients at the same time 5 Plain RTP is simpler to distribute in different topologies 6 You can take advantage of multicast networks easily 7 More in general, WebRTC has too much overhead for that

74. A specific scenario: broadcasting • Tree topology with several levels • Broadcaster is at the root • Intermediate levels are relayers (RTP trunks) • Attendees attached at edge nodes (WebRTC) • Waterfalls and Valves • Only one flow between related nodes • Different encodings can be different flows • Number of relay levels can vary • No levels → Broadcaster feeding edge nodes directly • 1-N levels → distribution network (unicast/simulcast) SOLEIL Streaming Of Large Scale Events over Internet cLouds

78. SOLEIL architecture: a simple overview

79. SOLEIL architecture: a simple overview

80. Another scenario: cascaded conferencing • Multiple VideoRoom instances “feeding” each other • Publisher on Janus X → relayed on other Janus instances too • Users can subscribe even when not on Janus X • Can be used for scaling purposes • Potential audience of publisher goes beyond capabilities of single Janus instance • Broadcasting seen before applied to conferencing, basically • Very interesting for geographic access to rooms too, though • Users always contact Janus closest to them • Behind the scenes, the Janus instances exchange media for all publishers • Typically, intra- and inter-datacenter network speed > Users network speed

83. Another scenario: cascaded conferencing

84. Another scenario: cascaded conferencing

85. A few words on nuts and bolts • We use Docker A LOT in our deployments • Even though Janus can deal with NATs, we do prefer it to have a public IP • Host networking makes it tricky to place more instances on the same machine • Pipework: assign a dedicated IP address to a container https://github.com/jpetazzo/pipework • Docker native macvlan network driver also allows you to assign custom IPs to containers. We’ll move to it sooner or later... • Several people (including us) using Janus in clustered environments (Docker Swarm, Kubernetes, ...) • Auto-scaling by spawning new replicas as needed • Live monitoring of machines’ resources (e.g., CPU, # connections, bandwidth) drives the deployment process

88. A real-world example

89. A real-world example

90. Thanks! Questions? Comments? Contacts • https://twitter.com/elminiero • https://twitter.com/meetecho • http://www.meetecho.com

Scaling WebRTC applications with Janus

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