Fix context cancelled during clean-up GOODBYE (#640)

* Make sure that the pool's asynchronous connection closure (`GOODBYE`) does
   not get cancelled when the acquisition of return of a connection that
   triggered the clean-up ends (and thus cancels the parent context).
 * Lower log level from error to debug on errors occurring during connection
   closure or when the connection is already dead.

Author: robsdedude

neo4j/internal/bolt/bolt4.go

@@ -189,6 +189,7 @@ func (b *bolt4) setError(err error, fatal bool) {
 		return
 	}
 
+	wasDead := b.state == bolt5Dead
 	// No previous error
 	if b.err == nil {
 		b.err = err
@@ -213,6 +214,8 @@ func (b *bolt4) setError(err error, fatal bool) {
 	neo4jErr, casted := err.(*db.Neo4jError)
 	if casted && neo4jErr.Classification() == "ClientError" {
 		b.log.Debugf(log.Bolt4, b.logId, "%s", err)
+	} else if wasDead {
+		b.log.Debugf(log.Bolt5, b.logId, "Already broken connection: %s", err)
 	} else {
 		b.log.Error(log.Bolt4, b.logId, err)
 	}

neo4j/internal/bolt/bolt5.go

@@ -200,6 +200,7 @@ func (b *bolt5) setError(err error, fatal bool) {
 		return
 	}
 
+	wasDead := b.state == bolt5Dead
 	// No previous error
 	if b.err == nil {
 		b.err = err
@@ -224,6 +225,8 @@ func (b *bolt5) setError(err error, fatal bool) {
 	neo4jErr, casted := err.(*db.Neo4jError)
 	if casted && neo4jErr.Classification() == "ClientError" {
 		b.log.Debugf(log.Bolt5, b.logId, "%s", err)
+	} else if wasDead {
+		b.log.Debugf(log.Bolt5, b.logId, "Already broken connection: %s", err)
 	} else {
 		b.log.Error(log.Bolt5, b.logId, err)
 	}

neo4j/internal/pool/pool.go

@@ -411,7 +411,20 @@ func (p *Pool) removeIdleOlderThanLocked(ctx context.Context, s *server, now tim
 func (p *Pool) closeConnection(ctx context.Context, c idb.Connection) {
 	p.ssrTracker.removeConnection(c)
 	// Close connection in another thread to avoid potential long blocking operation during close.
-	go c.Close(ctx)
+	go func() {
+		ctx, cancelFunc := context.WithTimeout(context.Background(), 30*time.Second)
+		defer cancelFunc()
+		c.Close(ctx)
+		if ctxErr := ctx.Err(); ctxErr != nil {
+			p.log.Debugf(
+				log.Pool,
+				p.logId,
+				"Connection %s timed out during graceful shutdown: %s",
+				c.ConnId(),
+				ctxErr,
+			)
+		}
+	}()
 }
 
 func (p *Pool) Return(ctx context.Context, c idb.Connection) {