OCR3 Commit Plugin

Context

The purpose of the OCR3 Commit Plugin is to write reports to a configured destination chain. These reports contain metadata of cross-chain messages, from a set of source chains, that can be executed on the destination chain.

Commit Plugin Design

The plugin is implemented as a state machine, and moves from state to state each round. There are 3 states:

1. SelectingIntervalsForReport
   • Determine intervals to be included in the next report
2. BuildingReport
   • Build a report from the intervals determined in the previous round
3. WaitingForReportTransmission
   • Check if the maximum committed sequence numbers on the dest chain have changed since generating the most recent report, i.e. check if the report has been committed.
   • If the maximum committed sequence numbers have changed (i.e. the report has been committed) or the maximum number of check attempts have been exhausted, move to the SelectingIntervalsForReport state and generate a new report.
   • If the maximum committed sequence numbers have not changed (i.e. the report is still in-flight) and the maximum number of check attempts are not been exhausted, move to the WaitingForReportTransmission state in order to check again.

This approach leads to a clear separation of concerns and addresses the complications that can arise if a report is not successfully transmitted (as we explicitly only continue once we know the previous report has been committed). In this design, full messages are no longer in the observations, only merkle roots and intervals are. This reduces the size of observations, which reduces bandwidth and improves performance.

This is the state machine diagram. States are in boxes, outcomes are within arrows.

          Start
            |
            V
-------------------------------
| SelectingIntervalsForReport | <---------|
-------------------------------           |
            |                             |
    ReportIntervalsSelected               |
            |                             |
            V                             |
    ------------------                    |
    | BuildingReport | -- ReportEmpty --->|
    ------------------                    |
            |                     ReportTransmitted
     ReportGenerated                     or
            |                    ReportNotTransmitted
            V                             |
--------------------------------          |
| WaitingForReportTransmission | -------->|
--------------------------------
        |           ^
        |           |
    ReportNotYetTransmitted