Summary

Adds weighted random steering to Graph Node’s Ethereum RPC provider selection, enabling per-endpoint load balancing with fractional weights and optional runtime control via a new CLI/config flag.

• add weighted random steering flag for Ethereum RPC providers
• allow provider entries to specify connection weights
• select RPC adapters using weighted random strategy

Key Changes

• Decimal weight configuration: RPC providers accept weights as f64 fractions (0.0–1.0), defaulting to 1.0.
• Weighted steering flag: --weighted-rpc-steering (and corresponding config option) toggles the new load-balancing strategy.
• Randomized adapter selection: Providers are chosen using a weighted distribution based on their configured fractions.
• Validation: Configuration rejects negative weights or values above 1.0.

Configuration Format

Enable weighted steering with custom fractions:

[chains.mainnet]
weighted_rpc_steering = true
provider = [
  { 
    label = "fast-node",
    details = { type = "web3", url = "https://fast.example", weight = 0.8 }
  },
  { 
    label = "backup-node",
    details = { type = "web3", url = "https://backup.example", weight = 0.2 }
  }
]

Weights omitted or set to 1.0 distribute traffic evenly.

Implementation Details

• Configuration: Added weight field and weighted_rpc_steering flag in node/src/config.rs with serde support.
• CLI: node/src/opt.rs exposes --weighted-rpc-steering flag.
• Network setup: node/src/network_setup.rs forwards weights to adapter creation.
• Ethereum adapter: chain/ethereum/src/network.rs implements weighted sampling logic in RPC selection.

Future Extensions

• Support dynamic weight updates without restarting the node.
• Expose metrics for per-provider utilization to tune weights automatically.
• Extend weighted steering to other chains or transport layers.

Test Plan

• Unit tests for configuration parsing of fractional weights.
• CLI integration tests for --weighted-rpc-steering.
• Manual verification against multiple RPC endpoints with uneven weights.
• (Pending) cargo test -p graph-node -p graph-chain-ethereum once protoc and proto dependencies are available.