Facebook Live Video讨论

想跟大家讨论一下Facebook Live Video这道题。
这是我在跟Google员工模拟面试的时候遇到的。
因为没准备过，答得不是特别好。

Facebook自己的讲解在这： Scaling Facebook Live Videos to a Billion Users
但是视频有点老了。2017年的，4年过去了。

我觉得这道题有几个考点

• Client - Server Communication 这里应该用什么Protocol。这里又细分两部分。这个网站有个比较全的列表：Streaming Protocols: Everything You Need to Know。现在还有一个比较新兴的技术叫做QUIC。目前几个大公司都在实验这个项技术。QUIC at Snap
  • Contribution / First Mile: Procotol to use from Streaming to Streaming Server.
  • Delivery / Last Mile: Protocol to use from Streaming Server to Friends / Followers.
• Video Encoding
• Unstable Network
  • Unstable Client Connection: Use Consistent hashing to pin upload streaming to a particular host
  • Limited Network bandwidth: Use Adaptive Bit Rate, Client-side caching, Audio-only Broadcast
  • Network partition inside data center: Use Consistent Hashing to find next host available for upload
• Load Distribution for Peak Traffic (streaming to 100k viewers)
  • Caching Manifest (in local data center / PoP). Use Cache Locking Timeout to avoid Thundering Hurd
  • CDN / Edge Servers