Relayer

The Relayer is a permissionless actor that submits cross chain messages to destination chains and monitors the Omni Consensus Layer until ⅔ (>66%) of the validator set attested to the next block on each source chain. It then submits the applicable cross-chain messages to each destination chain providing the quorum validator signatures and a multi-merkle-proof. Will be incentivized in future versions of the network.

The Relayer is also responsible for monitoring attestations. Similar to validators, relayers should maintain an XBlock cache. I.e., track all source chain blocks, convert them to XBlocks, cache them, and make them available for internal indexed querying. Relayers monitor the Omni Consensus Chain state for attested XBlock.

For each destination chain, the relayer has to decide how many XMsgs to submit, which defines the cost of transactions being submitted to the destination chain. This is primarily defined by the data size and gas limit of the messages and the portal contract verification and processing overhead.

A merkle-multi-proof is generated for the set of identified XMsgs that match the quorum XBlock attestations root. The relayer submits a EVM transaction to the destination chain, ensuring it gets included on-chain as soon as possible. The transaction contains the following data:

type Submission (
  AggregateAttestation att    // Aggregate attestation containing quorum signatures for a specific validator set.
  XMsg[]               msgs   // Subset of XMsgs in a XBlock (could also be all)
  bytes                Proofs // Merkle-multi-proof for XMsgBatch
)