The Livepeer network is an open marketplace where broadcasters are able to
select orchestrators to send work to based on their own preferences. The
algorithm for selecting orchestrators depends on the broadcaster implemention,
but all selection algorithms including the default implementation included in
livepeer consider the following factors:
The economic security provided by an orchestrator is measured by its total stake including its own self-delegated stake as well as the stake of its delegators. The more stake that an orchestrator has, the more economic security it provides to a broadcaster because the stake can be slashed if the work is performed incorrectly.
The default broadcaster implementation will bias towards selecting orchestrators that provide more economic security more often with the probability of an orchestrator receiving work being proportional to the orchestrator's stake relative to the rest of the orchestrators on the network. However, just because an orchestrator receives work does not necessarily mean it will retain work - if the orchestrator does not meet the requirements of the broadcaster for other selection factors, the orchestrator can lose the work after being initially selected.
The latency of an orchestrator is the total time for an orchestrator to return transcoded results to a broadcaster. This includes the time it takes for the broadcaster to upload a segment to the orchesterator, the time it takes for the orchestrator to transcode the segment (and in the case of a split orchestrator and transcoder this includes the network transit time between the orchestrator and transcoder) and the time it takes for the broadcaster to download the transcoded results from the orchestrator. The latency of an orchestrator will depend on its geographic proximity to the broadcaster, its hardware resources which impact transcoding speed and its bandwidth resources which impact upload/download speed.
The default broadcaster implementation will assess an orchestrator's latency after initial selection to determine whether to continue sending work to the orchestrator. The default requirement is for the transcoded results to be received within real-time meaning the round trip time needs to be less than or equal to the duration of segment. If an orchestrator that is initially selected fails to meet this requirement, it may stop receiving work from the broadcaster giving other orchestrators an opportunity to win work.
The selection algorithm in
livepeer is being improved over time and in the
future, there may be a variety of selection algorithms used in the network.
Additional factors that selection algorithms may consider include: