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optimism.md

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Running Reth on OP Stack chains

reth ships with the optimism feature flag in several crates, including the binary, enabling support for OP Stack chains out of the box. Optimism has a small diff from the L1 EELS, comprising of the following key changes:

  1. A new transaction type, 0x7E (Deposit), which is used to deposit funds from L1 to L2.
  2. Modifications to the PayloadAttributes that allow the sequencer to submit transactions to the EL through the Engine API. Payloads will be built with deposit transactions at the top of the block, with the first deposit transaction always being the "L1 Info Transaction."
  3. EIP-1559 denominator and elasticity parameters have been adjusted to account for the lower block time (2s) on L2. Otherwise, the 1559 formula remains the same.
  4. Network fees are distributed to the various fee vaults.
  5. ... and some other minor changes.

For a more in-depth list of changes and their rationale, as well as specifics about the OP Stack specification such as transaction ordering and more, see the documented op-geth diff, the L2 EL specification, and the OP Stack specification.

Running on Optimism

You will need three things to run op-reth:

  1. An archival L1 node, synced to the settlement layer of the OP Stack chain you want to sync (e.g. reth, geth, besu, nethermind, etc.)
  2. A rollup node (e.g. op-node, magi, hildr, etc.)
  3. An instance of op-reth.

For this example, we'll start a Base Mainnet node.

Installing op-reth

To run Reth on Optimism, first install op-reth via the Makefile in the workspace root:

git clone https://github.com/paradigmxyz/reth.git && \
    cd reth && \
    make install-op

This will install the op-reth binary to ~/.cargo/bin/op-reth.

Installing a Rollup Node

Next, you'll need to install a Rollup Node, which is the equivalent to the Consensus Client on the OP Stack. Available options include:

  1. op-node
  2. magi
  3. hildr

For the sake of this tutorial, we'll use the reference implementation of the Rollup Node maintained by OP Labs, the op-node. The op-node can be built from source, or pulled from a Docker image available on Google Cloud.

rethdb build tag
The op-node also comes with an experimental rethdb build tag, which allows it to read receipts directly from an L1 reth database during derivation. This can speed up sync times, but it is not required if you do not have access to the L1 archive node on the same machine as your L2 node.

To build the op-node with the rethdb build tag enabled:

git clone https://github.com/ethereum-optimism/optimism.git && \
    (cd optimism/op-service/rethdb-reader && cargo build --release) && \ 
    cd optimism/op-node && \
    go build -v -tags rethdb -o ./bin/op-node ./cmd/main.go && \
    mv bin/op-node /usr/bin/op-node

This will build the rethdb-reader dylib and instruct the op-node build to statically link this dylib into the binary. The op-node binary will be installed to /usr/bin/op-node.

Running op-reth

The optimism feature flag in op-reth adds several new CLI flags to the reth binary:

  1. --rollup.sequencer-http <uri> - The sequencer endpoint to connect to. Transactions sent to the op-reth EL are also forwarded to this sequencer endpoint for inclusion, as the sequencer is the entity that builds blocks on OP Stack chains.
  2. --rollup.disable-tx-pool-gossip - Disables gossiping of transactions in the mempool to peers. This can be omitted for personal nodes, though providers should always opt to enable this flag.
  3. --rollup.enable-genesis-walkback - Disables setting the forkchoice status to tip on startup, making the op-node walk back to genesis and verify the integrity of the chain before starting to sync. This can be omitted unless a corruption of local chainstate is suspected.
  4. --rollup.discovery.v4 - Enables the discovery v4 protocol for peer discovery. By default, op-reth, similar to op-geth, has discovery v5 enabled and discovery v4 disabled, whereas regular reth has discovery v4 enabled and discovery v5 disabled.

First, ensure that your L1 archival node is running and synced to tip. Also make sure that the beacon node / consensus layer client is running and has http APIs enabled. Then, start op-reth with the --rollup.sequencer-http flag set to the Base Mainnet sequencer endpoint:

op-reth node \
    --chain base \
    --rollup.sequencer-http https://mainnet-sequencer.base.org \
    --http \
    --ws \
    --authrpc.port 9551 \
    --authrpc.jwtsecret /path/to/jwt.hex

Then, once op-reth has been started, start up the op-node:

op-node \
    --network="base-mainnet" \
    --l1=<your-L1-rpc> \
    --l2=http://localhost:9551 \
    --l2.jwt-secret=/path/to/jwt.hex \
    --rpc.addr=0.0.0.0 \
    --rpc.port=7000 \
    --l1.beacon=<your-beacon-node-http-endpoint>
    --syncmode=execution-layer
    --l2.enginekind=reth

Consider adding the --l1.trustrpc flag to improve performance, if the connection to l1 is over localhost.

If you opted to build the op-node with the rethdb build tag, this feature can be enabled by appending one extra flag to the op-node invocation:

Note, the reth_db_path is the path to the db folder inside of the reth datadir, not the mdbx.dat file itself. This can be fetched from op-reth db path [--chain <chain-name>], or if you are using a custom datadir location via the --datadir flag, by appending /db to the end of the path.

op-node \
    # ...
    --l1.rethdb=<your_L1_reth_db_path>