refactor(client): skip some pool housekeeping on shared h2 handles

src/client/pool.rs

@@ -159,7 +159,7 @@ impl<T: Poolable> Pool<T> {
     }
 
     pub(super) fn pooled(&self, mut connecting: Connecting<T>, value: T) -> Pooled<T> {
-        let value = match value.reserve() {
+        let (value, pool_ref) = match value.reserve() {
             Reservation::Shared(to_insert, to_return) => {
                 debug_assert_eq!(
                     connecting.key.1,
@@ -174,24 +174,45 @@ impl<T: Poolable> Pool<T> {
                 // prevent the Drop of Connecting from repeating inner.connected()
                 connecting.pool = Weak::new();
 
-                to_return
+                // Shared reservations don't need a reference to the pool,
+                // since the pool always keeps a copy.
+                (to_return, Weak::new())
+            },
+            Reservation::Unique(value) => {
+                // Unique reservations must take a reference to the pool
+                // since they hope to reinsert once the reservation is
+                // completed
+                (value, Arc::downgrade(&self.inner))
             },
-            Reservation::Unique(value) => value,
         };
         Pooled {
             is_reused: false,
             key: connecting.key.clone(),
-            pool: Arc::downgrade(&self.inner),
+            pool: pool_ref,
             value: Some(value)
         }
     }
 
     fn reuse(&self, key: &Key, value: T) -> Pooled<T> {
         debug!("reuse idle connection for {:?}", key);
+        // TODO: unhack this
+        // In Pool::pooled(), which is used for inserting brand new connections,
+        // there's some code that adjusts the pool reference taken depending
+        // on if the Reservation can be shared or is unique. By the time
+        // reuse() is called, the reservation has already been made, and
+        // we just have the final value, without knowledge of if this is
+        // unique or shared. So, the hack is to just assume Ver::Http2 means
+        // shared... :(
+        let pool_ref = if key.1 == Ver::Http2 {
+            Weak::new()
+        } else {
+            Arc::downgrade(&self.inner)
+        };
+
         Pooled {
             is_reused: true,
             key: key.clone(),
-            pool: Arc::downgrade(&self.inner),
+            pool: pool_ref,
             value: Some(value),
         }
     }
@@ -216,15 +237,18 @@ impl<'a, T: Poolable + 'a> IdlePopper<'a, T> {
         while let Some(entry) = self.list.pop() {
             // If the connection has been closed, or is older than our idle
             // timeout, simply drop it and keep looking...
-            //
+            if entry.value.is_closed() {
+                trace!("removing closed connection for {:?}", self.key);
+                continue;
+            }
             // TODO: Actually, since the `idle` list is pushed to the end always,
             // that would imply that if *this* entry is expired, then anything
             // "earlier" in the list would *have* to be expired also... Right?
             //
             // In that case, we could just break out of the loop and drop the
             // whole list...
-            if entry.value.is_closed() || expiration.expires(entry.idle_at) {
-                trace!("remove unacceptable pooled connection for {:?}", self.key);
+            if expiration.expires(entry.idle_at) {
+                trace!("removing expired connection for {:?}", self.key);
                 continue;
             }
 
@@ -257,10 +281,10 @@ impl<T: Poolable> PoolInner<T> {
             return;
         }
         if key.1 == Ver::Http2 && self.idle.contains_key(&key) {
-            trace!("Pool::put; existing idle HTTP/2 connection for {:?}", key);
+            trace!("put; existing idle HTTP/2 connection for {:?}", key);
             return;
         }
-        trace!("Pool::put {:?}", key);
+        trace!("put; add idle connection for {:?}", key);
         let mut remove_parked = false;
         let mut value = Some(value);
         if let Some(parked) = self.parked.get_mut(&key) {
@@ -288,7 +312,7 @@ impl<T: Poolable> PoolInner<T> {
                     }
                 }
 
-                trace!("Pool::put removing canceled parked {:?}", key);
+                trace!("put; removing canceled waiter for {:?}", key);
             }
             remove_parked = parked.is_empty();
         }
@@ -306,7 +330,7 @@ impl<T: Poolable> PoolInner<T> {
                          idle_at: Instant::now(),
                      });
             }
-            None => trace!("Pool::put found parked {:?}", key),
+            None => trace!("put; found waiter for {:?}", key),
         }
     }
 
@@ -345,23 +369,26 @@ impl<T> PoolInner<T> {
 }
 
 impl<T: Poolable> PoolInner<T> {
+    /// This should *only* be called by the IdleInterval.
     fn clear_expired(&mut self) {
-        let dur = if let Some(dur) = self.timeout {
-            dur
-        } else {
-            return
-        };
+        let dur = self.timeout.expect("interval assumes timeout");
 
         let now = Instant::now();
         //self.last_idle_check_at = now;
 
-        self.idle.retain(|_key, values| {
-
+        self.idle.retain(|key, values| {
             values.retain(|entry| {
                 if entry.value.is_closed() {
+                    trace!("idle interval evicting closed for {:?}", key);
                     return false;
                 }
-                now - entry.idle_at < dur
+                if now - entry.idle_at > dur {
+                    trace!("idle interval evicting expired for {:?}", key);
+                    return false;
+                }
+
+                // Otherwise, keep this value...
+                true
             });
 
             // returning false evicts this key/val
@@ -459,9 +486,11 @@ impl<T: Poolable> Drop for Pooled<T> {
                 if let Ok(mut inner) = inner.lock() {
                     inner.put(self.key.clone(), value);
                 }
-            } else {
+            } else if self.key.1 == Ver::Http1 {
                 trace!("pool dropped, dropping pooled ({:?})", self.key);
             }
+            // Ver::Http2 is already in the Pool (or dead), so we wouldn't
+            // have an actual reference to the Pool.
         }
     }
 }