graph, store: Replace std::sync::RwLock with parking_lot::RwLock for pool metrics

Use parking_lot::RwLock instead of std::sync::RwLock for connection pool
metric recording. parking_lot::RwLock is faster for short-held locks as
it uses efficient spinning before parking, reducing tokio worker thread
blocking during metric recording.

This change helps reduce tokio threadpool contention when the connection
pool is under heavy load, as the metric recording locks are held for
only microseconds.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: lutter

graph/src/components/store/mod.rs

@@ -25,9 +25,11 @@ use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::fmt;
 use std::fmt::Display;
 use std::sync::atomic::{AtomicUsize, Ordering};
-use std::sync::{Arc, RwLock};
+use std::sync::Arc;
 use std::time::Duration;
 
+use crate::parking_lot::RwLock;
+
 use async_trait::async_trait;
 
 use crate::blockchain::{Block, BlockHash, BlockPtr};

graph/src/data/graphql/load_manager.rs

@@ -457,7 +457,7 @@ impl LoadManager {
     }
 
     fn overloaded(&self, wait_stats: &PoolWaitStats) -> (bool, Duration) {
-        let store_avg = wait_stats.read().unwrap().average();
+        let store_avg = wait_stats.read().average();
         let overloaded = store_avg
             .map(|average| average > ENV_VARS.load_threshold)
             .unwrap_or(false);

store/postgres/src/pool/manager.rs

@@ -22,9 +22,10 @@ use std::collections::HashMap;
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
 use std::sync::Arc;
-use std::sync::RwLock;
 use std::time::{Duration, Instant};
 
+use graph::parking_lot::RwLock;
+
 use crate::pool::AsyncPool;
 
 /// Our own connection manager. It is pretty much the same as
@@ -308,7 +309,6 @@ impl WaitMeter {
     pub(crate) fn add_conn_wait_time(&self, duration: Duration) {
         self.wait_stats
             .write()
-            .unwrap()
             .add_and_register(duration, &self.wait_gauge);
     }
 }

store/postgres/src/pool/mod.rs

@@ -19,11 +19,13 @@ use graph::slog::warn;
 use graph::util::timed_rw_lock::TimedMutex;
 use tokio::sync::OwnedSemaphorePermit;
 
+use std::collections::HashMap;
 use std::fmt::{self};
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 use std::time::Duration;
-use std::{collections::HashMap, sync::RwLock};
+
+use graph::parking_lot::RwLock;
 
 use crate::catalog;
 use crate::pool::manager::{ConnectionManager, WaitMeter};
@@ -720,7 +722,6 @@ impl PoolInner {
         let permit = self.query_semaphore.cheap_clone().acquire_owned().await;
         self.semaphore_wait_stats
             .write()
-            .unwrap()
             .add_and_register(start.elapsed(), &self.semaphore_wait_gauge);
         permit.unwrap()
     }
@@ -734,7 +735,6 @@ impl PoolInner {
         let elapsed = start.elapsed();
         self.indexing_semaphore_wait_stats
             .write()
-            .unwrap()
             .add_and_register(elapsed, &self.indexing_semaphore_wait_gauge);
         (permit.unwrap(), elapsed)
     }