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Scheduler

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

Features​

  • Based on the multi-feature intelligent scheduling system selects the optimal parent peer.
  • Build a scheduling directed acyclic graph for the P2P cluster.
  • Remove abnormal peer based on peer multi-feature evaluation results.
  • In the case of scheduling failure, notice peer back-to-source download.
  • Provide metadata storage to support file writing and seeding.

Scheduling​

Scheduler maintains task, peer and host resources.

  • Peer: a download task for Client
  • Host: host information for Client, 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 directed acyclic graph according to the peer's load.

scheduler-dag

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