Orchestration: Checkpointing process

[adlrocha]

Background

Every check_period epochs, the state of a child subnet C must be checkpointed in its parent subnet P. A checkpoint for some epoch e includes metadata (e.g., subnet ID, epoch, etc.) and a proof of the state of C at epoch e. The form of this proof is an implementation detail of the respective subnet.

The validators of the subnet C are responsible for generating the proof. Its exact form and the number of validators involved in its generation is an implementation detail of the subnet. As of the time of this writing, in our reference implementation, this proof consists of the signatures of more than two-thirds of the validators of C.

The IPC Agent actively acts on behalf of one or more validators to orchestrate the general checkpointing activity. This includes constructing the checkpoint data, collecting proofs from the validators, and submitting the checkpoint to the subnet actor of C deployed on the parent subnet P. At a high level, for every account A on subnet C associated with the agent, the agent conducts the following steps:

• Monitor subnet C for checkpoint epochs.
• For every checkpoint epoch e:
• Check if A is a validator at epoch e.
• If yes, then build the checkpoint metadata.
• Request a proof from A for the checkpoint.
• Submit the checkpoint, consisting of the metadata and the proof, to the subnet actor of C on P.

Subnet manager command

• checkpoint list: Lists all the checkpoints committed for a range of blocks for a subnet C.