Catchup API

Serves recent consensus state to allow peers to catch up with the network

The primary customer of this API is peer consensus nodes who may have recently joined the network or were temporarily disconnected. These nodes need the very latest state, one which hasn't even been finalized yet, in order to start voting and proposing in consensus.

In HotShot, all state required to participate is represented in the form of Merkle trees or Merkle tries, so this API is able to provide select segments of the state with a proof that will convince the client that the returned segment is accurate, as long as they know the corresponding state commitment.

Types

Account

{
    // Account balance in WEI. Serialized as a hex string so as not to exceed the
    // range of JSON integers.
    "balance": hex,
    // Merkle proof justifying "balance" relative to the state commitment.
    "proof": {
        "account": hex,
        "proof":
            { "Presence": MerkleProof },
          | { "Absence": MerkleProof }
        }
    }       
}

Endpoints

GET /catchup/:height/:view/account/:address

Get the balance of the requested fee account in the state from the requested consensus height and view. This is used to fetch the state for unfinalized views, to facilitate rapid catchup. If :view has already been finalized, this endpoint may fail with error 404.

:height and :view must correspond! :height is provided to simplify lookups for backends where data is not indexed by view.

Parameters

Name	Type	Description
height	integer	The block height at which to look up the account balance
view	integer	The view from which to look up the account balance
address	hex	The account (Ethereum address) to look up

Returns Account

POST /catchup/:height/:view/accounts

Bulk version of /catchup/:height/:view/account. The request body should be a JSON array consisting of TaggedBase64-encoded fee accounts.

The response is a FeeMerkleTree containing sub-trees for each of the requested accounts, which is a more condensed way to represent the union of account proofs for each requested account. Individual Merkle proofs for each account can be extracted from this tree.

:height and :view must correspond! :height is provided to simplify lookups for backends where data is not indexed by view.

Parameters

Name	Type	Description
height	integer	The block height at which to look up the account balance
view	integer	The view from which to look up the account balance

Returns FeeMerkleTree

GET /catchup/:height/:view/blocks

Get the Merkle frontier (path to most recently inserted element) of the accumulator of blocks, from the requested consensus view. This is used to fetch the state for unfinalized views, to facilitate rapid catchup. If :view has already been finalized, this endpoint may fail with error 404.

:height and :view must correspond! :height is provided to simplify lookups for backends where data is not indexed by view.

Parameters

Name	Type	Description
height	integer	The block height at which to look up the frontier
view	integer	The view from which to look up the frontier

Returns MerkleProof

GET /catchup/chain-config/:commitment

Get the chain config with the given hash.

Parameters

Name	Type	Description
commitment	tagged<CHAIN_CONFIG>	The hash of the chain config to look up

Returns ChainConfig