feat: per-address gas limit feature

src/gas_limiter/args.rs

@@ -0,0 +1,28 @@
+use clap::Args;
+
+#[derive(Debug, Clone, Default, PartialEq, Eq, Args)]
+pub struct GasLimiterArgs {
+    /// Enable address-based gas rate limiting
+    #[arg(long = "gas-limiter.enabled", env)]
+    pub gas_limiter_enabled: bool,
+
+    /// Maximum gas per address in token bucket. Defaults to 10 million gas.
+    #[arg(
+        long = "gas-limiter.max-gas-per-address",
+        env,
+        default_value = "10000000"
+    )]
+    pub max_gas_per_address: u64,
+
+    /// Gas refill rate per block. Defaults to 1 million gas per block.
+    #[arg(
+        long = "gas-limiter.refill-rate-per-block",
+        env,
+        default_value = "1000000"
+    )]
+    pub refill_rate_per_block: u64,
+
+    /// How many blocks to wait before cleaning up stale buckets for addresses.
+    #[arg(long = "gas-limiter.cleanup-interval", env, default_value = "100")]
+    pub cleanup_interval_blocks: u64,
+}

src/gas_limiter/error.rs

@@ -0,0 +1,13 @@
+use alloy_primitives::Address;
+
+#[derive(Debug, thiserror::Error)]
+pub enum GasLimitError {
+    #[error(
+        "Address {address} exceeded gas limit: {requested} gwei requested, {available} gwei available"
+    )]
+    AddressLimitExceeded {
+        address: Address,
+        requested: u64,
+        available: u64,
+    },
+}

src/gas_limiter/metrics.rs

@@ -0,0 +1,46 @@
+use std::time::Duration;
+
+use metrics::{Counter, Gauge, Histogram};
+
+use crate::prelude::*;
+use crate::gas_limiter::error::GasLimitError;
+
+#[derive(MetricsSet)]
+pub(super) struct GasLimiterMetrics {
+    /// Transactions rejected by gas limits Labeled by reason: "per_address",
+    /// "global", "burst"
+    pub rejections: Counter,
+
+    /// Time spent in rate limiting logic
+    pub check_time: Histogram,
+
+    /// Number of addresses with active budgets
+    pub active_address_count: Gauge,
+
+    /// Time to refill buckets
+    pub refresh_duration: Histogram,
+}
+
+impl GasLimiterMetrics {
+    pub(super) fn record_gas_check(
+        &self,
+        check_result: &Result<bool, GasLimitError>,
+        duration: Duration,
+    ) {
+        if let Ok(created_new_bucket) = check_result {
+            if *created_new_bucket {
+                self.active_address_count.increment(1);
+            }
+        } else {
+            self.rejections.increment(1);
+        }
+
+        self.check_time.record(duration);
+    }
+
+    pub(super) fn record_refresh(&self, removed_addresses: usize, duration: Duration) {
+        self.active_address_count
+            .decrement(removed_addresses as f64);
+        self.refresh_duration.record(duration);
+    }
+}