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Alternative Mempools

P2P mempool

Disclaimer: Content created from source code using generative AI. Contact us for clarifications or if you find mistakes in this document.

Running ./skandha node instead of ./skandha standalone joins a libp2p network that gossips Frame Transactions between sidecar nodes. Gossipsub handles propagation and discv5 handles peer discovery.

Wire format version

Section titled “Wire format version”

Nodes must run the same wire format to share a mempool. Adding keyed nonces (EIP-8250) and recent-root references (EIP-8272) changed the SSZ FrameTransaction, so both protocols that carry it were versioned.

Protocol Before Now
Gossip topic /account_abstraction/<mempool>/frame_transaction/ssz_snappy …/frame_transaction_v2/ssz_snappy
Req/resp pooled_frame_txs_by_hash version 1 version 2

Old and new nodes simply do not exchange Frame Transactions. Upgrade every node of a network together. The other req/resp protocols (pooled_frame_tx_hashes, status, ping, metadata, goodbye) are unchanged.

Walkthrough

Section titled “Walkthrough”

This is a bootnode and a regular node against a local ethrex devnet.

  1. Build and start ethrex from the eip8141-tracer branch. It does not build natively on macOS, so test/e2e/ethrex-devnet.sh builds and runs it in Docker: ./test/e2e/ethrex-devnet.sh build once, then ./test/e2e/ethrex-devnet.sh up. It listens on http://127.0.0.1:8555 with chain ID 9 and the ethrex API namespace enabled.

  2. Configure the bootnode. Create nodeA/config.json with the sentinel entry point address, the standard mempool ID, a funded relayer key and rpcEndpoint set to http://127.0.0.1:8555. See Run the sidecar.

  3. Run the bootnode:

    Terminal window
    bun --bun packages/cli/bin/skandha.js node \
      --configFile ./nodeA/config.json --dataDir ./nodeA \
      --api.address 127.0.0.1 --api.port 14337 --api.wsPort 14337 \
      --p2p.host 127.0.0.1 --p2p.enrHost 127.0.0.1 --p2p.port 4337 --p2p.enrPort 4337 \
      --p2p.retainPeerId \
      --executor.bundlingMode manual

    --api.wsPort defaults to 14337 and does not follow --api.port. Set it explicitly. --p2p.retainPeerId persists the node’s ENR to ./nodeA/enr.

  4. Read the ENR with cat ./nodeA/enr.

  5. Run the second node with its own config, data directory and ports, and --p2p.bootEnrs <the ENR>. Use ports 14338 and 4338 on the same machine.

  6. Confirm the nodes peered. Gossipsub silently drops a publish with no subscribed peers. Call skandha_connectedPeers on both nodes and wait for a non-empty array.

  7. Submit a Frame Transaction to node A with eth_sendFrameTransaction. See Submit a Frame Transaction.

  8. Confirm it reached node B with eth_getFrameTransactionByHash on node B’s RPC. A non-null result proves the transaction was published by gossip and that node B validated it and stored it in its own mempool.

Automated version

Section titled “Automated version”
Terminal window
./test/e2e/ethrex-devnet.sh build   # once
bun run build
bun run test:e2e

Connecting to the public devnet

Section titled “Connecting to the public devnet”

A sidecar can peer with the devnet’s mempool by using the devnet’s ENR as a boot node. See deploy/devnet/devnet-readme.md in the sidecar repository for the ENR and flags.