feat(txpool): add sub-pools length and size metrics (#2598)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/transaction-pool/src/metrics.rs

@@ -1,6 +1,6 @@
 //! Transaction pool metrics.
 
-use metrics::Counter;
+use metrics::{Counter, Gauge};
 use reth_metrics_derive::Metrics;
 
 /// Transaction pool metrics
@@ -13,4 +13,19 @@ pub struct TxPoolMetrics {
     pub(crate) invalid_transactions: Counter,
     /// Number of removed transactions from the pool
     pub(crate) removed_transactions: Counter,
+
+    /// Number of transactions in the pending sub-pool
+    pub(crate) pending_pool_transactions: Gauge,
+    /// Total amount of memory used by the transactions in the pending sub-pool in bytes
+    pub(crate) pending_pool_size_bytes: Gauge,
+
+    /// Number of transactions in the basefee sub-pool
+    pub(crate) basefee_pool_transactions: Gauge,
+    /// Total amount of memory used by the transactions in the basefee sub-pool in bytes
+    pub(crate) basefee_pool_size_bytes: Gauge,
+
+    /// Number of transactions in the queued sub-pool
+    pub(crate) queued_pool_transactions: Gauge,
+    /// Total amount of memory used by the transactions in the queued sub-pool in bytes
+    pub(crate) queued_pool_size_bytes: Gauge,
 }

crates/transaction-pool/src/pool/txpool.rs

@@ -253,9 +253,23 @@ impl<T: TransactionOrdering> TxPool<T> {
         // Process the sub-pool updates
         let UpdateOutcome { promoted, discarded } = self.process_updates(updates);
 
+        // update the metrics after the update
+        self.update_size_metrics();
+
         OnNewCanonicalStateOutcome { block_hash, mined: mined_transactions, promoted, discarded }
     }
 
+    /// Update sub-pools size metrics.
+    pub(crate) fn update_size_metrics(&mut self) {
+        let stats = self.size();
+        self.metrics.pending_pool_transactions.set(stats.pending as f64);
+        self.metrics.pending_pool_size_bytes.set(stats.pending_size as f64);
+        self.metrics.basefee_pool_transactions.set(stats.basefee as f64);
+        self.metrics.basefee_pool_size_bytes.set(stats.basefee_size as f64);
+        self.metrics.queued_pool_transactions.set(stats.queued as f64);
+        self.metrics.queued_pool_size_bytes.set(stats.queued_size as f64);
+    }
+
     /// Adds the transaction into the pool.
     ///
     /// This pool consists of two three-pools: `Queued`, `Pending` and `BaseFee`.

docs/design/metrics.md

@@ -75,8 +75,14 @@ This list may be non-exhaustive.
 #### Component: Transaction Pool
 
 - `transaction_pool.inserted_transactions`: Number of transactions inserted in the pool
-- `transaction_pool.invalid_transactions`: Number of invalid transactions 
+- `transaction_pool.invalid_transactions`: Number of invalid transactions
 - `transaction_pool.removed_transactions`: Number of removed transactions from the pool
+- `transaction_pool.pending_pool_transactions`: Number of transactions in the pending sub-pool
+- `transaction_pool.pending_pool_size_bytes`: Total amount of memory used by the transactions in the pending sub-pool in bytes
+- `transaction_pool.basefee_pool_transactions`: Number of transactions in the basefee sub-pool
+- `transaction_pool.basefee_pool_size_bytes`: Total amount of memory used by the transactions in the basefee sub-pool in bytes
+- `transaction_pool.queued_pool_transactions`: Number of transactions in the queued sub-pool
+- `transaction_pool.queued_pool_size_bytes`: Total amount of memory used by the transactions in the queued sub-pool in bytes
 
 #### Component: Network