Parachains Finality Relay
Source Relay Chain is running GRANDPA Finality Gadget. Source Parachain is a parachain of the Source
Relay Chain. Bridge GRANDPA finality pallet is deployed at Target Chain runtime and is "connected"
to the Source Relay Chain. Bridge Parachains finality pallet is deployed at Target Chain and is
configured to track the Source Parachain. GRANDPA Relayer is configured to relay Source Relay Chain
finality to Target Chain. Parachains Relayer is configured to relay Source Parachain headers finality
to Target Chain.
sequenceDiagram
participant Source Parachain
participant Source Relay Chain
participant GRANDPA Relayer
participant Parachains Relayer
participant Target Chain
Note left of Source Parachain: Best: 125
Note left of Source Relay Chain: Finalized: 500, Best Parachain at Finalized: 120
Note right of Target Chain: Best Relay: 480, Best Parachain: 110
Source Parachain ->> Source Parachain: Import Block 126
Source Parachain ->> Source Relay Chain: Receives the Parachain block 126
Source Relay Chain ->> Source Relay Chain: Import block 501
Source Relay Chain ->> Source Relay Chain: Finalize block 501
Note left of Source Relay Chain: Finalized: 501, Best Parachain at Finalized: 126
Source Relay Chain ->> Parachains Relayer: notes new Source Parachain Block 126
Note left of Parachains Relayer: can't relay Source Parachain Block 126, because it requires at least Source Relay Block 501 at Target Chain
Source Relay Chain ->> Source Relay Chain: Import block 502
Source Relay Chain ->> Source Relay Chain: Finalize block 502
Source Relay Chain ->> GRANDPA Relayer: read GRANDPA Finality Proof of Block 502
GRANDPA Relayer ->> Target Chain: submit GRANDPA Finality Proof of Block 502
Note right of Target Chain: Best Relay: 502, Best Parachain: 110
Target Chain ->> Parachains Relayer: notes finalized Source Relay Block 502 at Target Chain
Source Relay Chain ->> Parachains Relayer: read Parachain Finality Proof at Relay Block 502
Parachains Relayer ->> Target Chain: submit Parachain Finality Proof at Relay Block 502
Note right of Target Chain: Best Relay: 502, Best Parachain: 126