rbuilder

rbuilder is an open-source, blazingly fast, cutting edge implementation of a Ethereum MEV-Boost block builder written in Rust. It is designed to provide a delightful developer experience, enabling community members to contribute and researchers to use rbuilder to study block building.

Features

• Multiple algorithms: Can be upgraded to handle several block building algorithms. The included algorithm builds blocks by sorting the orders by either effective gas price or total profit and then trying (they might fail!) to execute them to create the block. For more details see ordering_builder.rs
• Backtesting: support for quick and easy backtesting on mempool transactions and other data
• Bundle merging: bundles that target transactions which have already been included in a pending block can be dropped if they are marked in reverting_tx_hashes.
• Smart nonce management: identifies and smartly handles nonce dependencies between bundles and transactions
• Using Reth: leverages fast, efficient and user-friendly Ethereum node written in Rust
• Reproducible builds

Running rbuilder

rbuilder can be run in two modes:

• Backtesting: build blocks on historical data. rbuilder leverages the mempool-dumpster's open database of transactions to let anyone easily backtest block building on previous blocks.
• Live: build and submit blocks to MEV-Boost relays in real time.

Backtesting

rbuilder supports backtesting against historical blocks. It does this by using the mempool-dumpster for historical mempool transactions to let anyone run rbuilder. If you have historical bundles, you can also plug that in for testing purposes. Moreover, rbuilder pulls the on-chain block to compare local block building against what actually landed. Finally, rbuilder stores historical data locally in an SQLite database to support rapid testing and iteration,

For more details on how to use rbuilder for backtesting, see https://github.com/flashbots/rbuilder/wiki/Noob-Guide-for-Backtesting

Live

To run rbuilder you need:

• Reth node for state. (reth_datadir)
• Reth node must expose ipc interface for mempool tx subscription (el_node_ipc_path).
• CL node that triggers new payload events (it must be additionally configured to trigger payload event every single time).
• Source of bundles that sends eth_sendBundle, mev_sendBundle, eth_sendRawTransaction as JSON rpc calls. (jsonrpc_server_port) (by default rbuilder will take raw txs from the reth node mempool)
• Relays so submit to (relays)
• Alternatively it can submit to the block validation API if run in the dry run mode (dry_run, dry_run_validation_url)

A sample configuration for running Lighthouse and triggering payload events would be:

./target/maxperf/lighthouse bn \
    --network mainnet \
    --execution-endpoint http://localhost:8551 \
    --execution-jwt /secrets/jwt.hex \
    --checkpoint-sync-url https://mainnet.checkpoint.sigp.io \
    --disable-deposit-contract-sync \
    --http \
    --http-port 3500 \
    --always-prepare-payload \
    --prepare-payload-lookahead 8000 \
    --suggested-fee-recipient 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045

Additionally, you can:

• configure block processor API as a sink for submitted blocks (blocks_processor_url)
• setup Prometheus / Grafana for metrics (served on telemetry_port + /debug/metrics/prometheus)
• record traces of all events happening inside the builder (tracing_path, served on telemetry_port + /debug/tracing/{start,stop})

Running:

1. Prepare config file based on the config-live-example.toml
2. Run rbuilder run PATH_TO_CONFIG_FILE

Warning: Even if they are rare, before running a builder you should be aware of reorg losses.

Benchmarking

rbuilder has a solid initial benchmarking setup (based on Criterion.rs).

• All PRs receive a benchmark report like this.
• You can run benchmarks with make bench and open the Criterion-generated report with make bench-report-open.
• Benchmarks are located in crates/rbuilder/benches. We'd love to add more meaningful benchmarks there!
• Let us know about further improvement ideas and additional relevant benchmarks.

End-to-end local testing

You can use builder-playground to deploy a fully functional local setup for the builder (Lighthouse consensus client (proposer + validator) + Reth execution client + MEV-Boost-Relay)) to test rbuilder.

First, start builder-playground:

git clone [email protected]:flashbots/builder-playground.git
cd builder-playground
go run main.go

Then, run rbuilder using the config-playground.toml config file:

cargo run --bin rbuilder run config-playground.toml

You can query the local relay for proposed blocks like this:

curl http://localhost:5555/relay/v1/data/bidtraces/proposer_payload_delivered

Reproducible builds

You only need to set the SOURCE_DATE_EPOCH environment variable to ensure that the build is reproducible:

# Use last commit timestamp as the build date
$ export SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct)

# build #1
$ rm -rf target/
$ cargo build --release
$ sha256sum target/release/rbuilder
d92ac33b94e16ed4a035b9dd52108fe78bd9bb160a91fced8e439f59b84c3207  target/release/rbuilder

# build #2
$ rm -rf target/
$ cargo build --release
$ sha256sum target/release/rbuilder
d92ac33b94e16ed4a035b9dd52108fe78bd9bb160a91fced8e439f59b84c3207  target/release/rbuilder

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Release Stability and Development Process

rbuilder is running in production at Flashbots since Q1 2024, and is reasonably stable. It is under active (and sometimes heavy) development, as we are constantly adding new features and improvements.

We encourage users to choose the version that best fits their needs: the latest stable release for production use, or the develop branch for those who want to test the latest features and are comfortable with potential instability.

Develop Branch

The develop branch is our main integration branch for ongoing development:

• We frequently merge pull requests into this branch.
• While we strive for quality, the develop branch may occasionally be unstable.
• There are no guarantees that code in this branch is fully tested or production-ready.

Stable Releases

For users seeking stability:

• We recommend using the latest tagged release.
• Each release undergoes thorough testing in production environments before publication.
• Tagged releases offer a higher level of reliability and are suitable for production use.
• You can find the stable releases at github.com/flashbots/rbuilder/releases

Release Cadence

We plan to cut a stable release at least once a month, but this may vary depending on the volume of changes and the stability of the codebase. To get notified, watch the repository, and you'll get an email notification on new releases.

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Contributing

We welcome contributions to rbuilder! Our contributor guidelines can be found in CONTRIBUTING.md.

Start by cloning the repo, and running a few common commands:

git clone [email protected]:flashbots/rbuilder.git
cd rbuilder

# Run linter
make lint

# Run tests
make test

# Run benchmarks and open the report
make bench
make bench-report-open

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Security

See SECURITY.md

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Acknowledgements

Big shoutout to the Reth team for building a kick-ass Ethereum node.

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Various notes

make build builds a bunch of additional binaries:

Binary	Description
rbuilder	Live block builder
backtest-build-block	Run backtests for a single block
backtest-build-range	Run backtests for a range of block
backtest-fetch	Download data for backtesting
dummy-builder	Simple sample builder to show how to plugin a custom BlockBuildingSink and BlockBuildingAlgorithm
misc-relays-slot	Shows info about winning bid for the block
debug-bench-machine	Tests execution performance
debug-order-input	Observe input of the bundles and transactions
debug-order-sim	Observe simulation of the bundles and transactions
debug-slot-data-generator	Shows new payload jobs coming from CL with attached data from relays.