Rollup Boost

Rollup Boost is a block builder sidecar for Optimism Stack chains to enable external block production. To read more about the design, check out the design doc.

Usage

Run the rollup-boost server using the following command:

cargo run -- [OPTIONS]

Command-line Options

• --l2-jwt-token <TOKEN>: JWT token for L2 authentication (required)
• --l2-jwt-path <PATH>: Path to the L2 JWT secret file (required if --l2-jwt-token is not provided)
• --l2-url <URL>: URL of the local L2 execution engine (required)
• --builder-url <URL>: URL of the builder execution engine (required)
• --builder-jwt-token <TOKEN>: JWT token for builder authentication (required)
• --builder-jwt-path <PATH>: Path to the builder JWT secret file (required if --builder-jwt-token is not provided)
• --rpc-host <HOST>: Host to run the server on (default: 0.0.0.0)
• --rpc-port <PORT>: Port to run the server on (default: 8081)
• --tracing: Enable tracing (default: false)
• --log-level <LEVEL>: Log level (default: info)
• --log-format <FORMAT>: Log format (default: text)
• --metrics: Enable metrics (default: false)
• --no-boost-sync: Disables using the proposer to sync the builder node (default: true)

Environment Variables

You can also set the options using environment variables. See .env.example to use the default values.

Example

cargo run --l2-jwt-token your_jwt_token --l2-url http://localhost:8545 --builder-jwt-token your_jwt_token --builder-url http://localhost:8546

Core System Workflow

1. rollup-boost receives an engine_FCU with the attributes to initiate block building:
   • It relays the call to proposer op-geth as usual and multiplexes the call to builder.
   • The FCU call returns the proposer payload id and internally maps the builder payload id to proposer payload id in the case the payload ids are not the same.
2. When rollup-boost receives an engine_getPayload:
   • It queries proposer op-geth for a fallback block.
   • In parallel, it queries builder for a block.
3. Upon receiving the builder block:
   • rollup-boost validates the block with proposer op-geth using engine_newPayload.
   • This validation ensures the block will be valid for proposer op-geth, preventing network stalls due to invalid blocks.
   • If the external block is valid, it is returned to the proposer op-node. Otherwise, rollup-boost will return the fallback block.
4. The proposer op-node sends a engine_newPayload request to rollup-boost and another engine_FCU without attributes to update chain state.
   • rollup-boost just relays the calls to proposer op-geth.
   • Note that since we already called engine_newPayload on the proposer op-geth in the previous step, the block should be cached and add minimal latency.
   • The builder op-node will receive blocks via p2p gossip and keep the builder node in sync via the engine api.

sequenceDiagram
    box Proposer
        participant op-node
        participant rollup-boost
        participant op-geth
    end
    box Builder
        participant builder-op-node as op-node
        participant builder-op-geth as builder
    end

    Note over op-node, builder-op-geth: 1. Triggering Block Building
    op-node->>rollup-boost: engine_FCU (with attrs)
    rollup-boost->>op-geth: engine_FCU (with attrs)
    rollup-boost->>builder-op-geth: engine_FCU (with attrs)
    rollup-boost->>op-node: proposer payload id

    Note over op-node, builder-op-geth: 2. Get Local and Builder Blocks
    op-node->>rollup-boost: engine_getPayload
    rollup-boost->>op-geth: engine_getPayload
    rollup-boost->>builder-op-geth: engine_getPayload

    Note over op-node, builder-op-geth: 3. Validating and Returning Builder Block
    rollup-boost->>op-geth: engine_newPayload
    op-geth->>rollup-boost: block validity
    rollup-boost->>op-node: block payload

    Note over op-node, builder-op-geth: 4. Updating Chain State
    op-node->>rollup-boost: engine_newPayload
    rollup-boost->>op-geth: engine_newPayload
    op-node->>rollup-boost: engine_FCU (without attrs)
    rollup-boost->>op-geth: engine_FCU (without attrs)

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RPC Calls

By default, rollup-boost will proxy all RPC calls from the proposer op-node to its local op-geth node. These are the list of RPC calls that are proxied to both the proposer and the builder execution engines:

• engine_forkchoiceUpdatedV3: this call is only multiplexed to the builder if the call contains payload attributes and the no_tx_pool attribute is false.
• engine_getPayloadV3: this is used to get the builder block.
• miner_*: this allows the builder to be aware of changes in effective gas price, extra data, and DA throttling requests from the batcher.
• eth_sendRawTransaction*: this forwards transactions the proposer receives to the builder for block building. This call may not come from the proposer op-node, but directly from the rollup's rpc engine.

Boost Sync

By default, rollup-boost will sync the builder with the proposer op-node. After the builder is synced, boost sync improves the performance of keeping the builder in sync with the tip of the chainby removing the need to receive chain updates via p2p via the builder op-node. This entails additional engine api calls that are multiplexed to the builder from rollup-boost:

• engine_forkchoiceUpdatedV3: this call will be multiplexed to the builder regardless of whether the call contains payload attributes or not.
• engine_newPayloadV3: ensures the builder has the latest block if the local payload was used.

License

The code in this project is free software under the MIT License.

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