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Version: v2.0.2

Scheduler

Scheduler selects the optimal parent peer for current peer to be downloaded and triggers the CDN back-to-source download or dfdaemon back-to-source download at the appropriate time.

Features​

  • Scheduler selects the optimal parent peer
  • Build a scheduling tree for the P2P cluster
  • Evaluate peers based on different features
  • In the case of scheduling failure, let dfdaemon back-to-source download

Scheduling​

Scheduler maintains task, peer and host resources.

  • Peer: a download task for dfdaemon
  • Host: host information for dfdaemon, host and peer have a 1:N relationship
  • Task: a download task, task and peer have a 1:N relationship

The scheduling process is actually to build a tree according to the peer's load.

scheduler-tree

Peer State Machine​

The scheduler divides tasks into three types Tiny, Small and Normal.

  • Tiny: file size is less than 128 bytes
  • Small: only one piece task
  • Normal: tasks with more than one piece

Different scheduling strategies are used for different types of download tasks, following state transition diagram during the peer scheduling process.

scheduler-state-machine