Add MaxConnLifetime config setting to pool in v3

conn.go

@@ -224,6 +224,7 @@ func (cc *ConnConfig) networkAddresses() ([]net.Addr, error) {
 // goroutines.
 type Conn struct {
 	conn               net.Conn  // the underlying TCP or unix domain socket connection
+	creationTime       time.Time // the time indicating when the connection is established
 	lastActivityTime   time.Time // the last time the connection was used
 	wbuf               []byte
 	pid                uint32            // backend pid
@@ -457,7 +458,7 @@ func connect(config ConnConfig, connInfo *pgtype.ConnInfo) (c *Conn, err error)
 		}
 
 		c.addr = addr
-
+		c.creationTime = time.Now()
 		return c, nil
 	}
 
@@ -602,6 +603,10 @@ func (c *Conn) connect(config ConnConfig, network, address string, tlsConfig *tl
 	}
 }
 
+func (c *Conn) CreationTime() time.Time {
+	return c.creationTime
+}
+
 func initPostgresql(c *Conn) (*pgtype.ConnInfo, error) {
 	const (
 		namedOIDQuery = `select t.oid,

conn_pool.go

@@ -13,9 +13,10 @@ import (
 
 type ConnPoolConfig struct {
 	ConnConfig
-	MaxConnections int               // max simultaneous connections to use, default 5, must be at least 2
-	AfterConnect   func(*Conn) error // function to call on every new connection
-	AcquireTimeout time.Duration     // max wait time when all connections are busy (0 means no timeout)
+	MaxConnections  int               // max simultaneous connections to use, default 5, must be at least 2
+	MaxConnLifetime time.Duration     // the duration since creation after which a connection will be automatically closed.
+	AfterConnect    func(*Conn) error // function to call on every new connection
+	AcquireTimeout  time.Duration     // max wait time when all connections are busy (0 means no timeout)
 }
 
 type ConnPool struct {
@@ -25,6 +26,7 @@ type ConnPool struct {
 	config               ConnConfig // config used when establishing connection
 	inProgressConnects   int
 	maxConnections       int
+	maxConnLifetime      time.Duration
 	resetCount           int
 	afterConnect         func(*Conn) error
 	logger               Logger
@@ -60,6 +62,7 @@ func NewConnPool(config ConnPoolConfig) (p *ConnPool, err error) {
 	p.config = config.ConnConfig
 	p.connInfo = minimalConnInfo
 	p.maxConnections = config.MaxConnections
+	p.maxConnLifetime = config.MaxConnLifetime
 	if p.maxConnections == 0 {
 		p.maxConnections = 5
 	}
@@ -226,7 +229,7 @@ func (p *ConnPool) Release(conn *Conn) {
 
 	p.cond.L.Lock()
 
-	if conn.poolResetCount != p.resetCount {
+	if conn.poolResetCount != p.resetCount || (p.maxConnLifetime != 0 && time.Now().Sub(conn.CreationTime()) > p.maxConnLifetime) {
 		conn.Close()
 		p.cond.L.Unlock()
 		p.cond.Signal()

conn_pool_test.go

@@ -15,6 +15,7 @@ import (
 
 func createConnPool(t *testing.T, maxConnections int) *pgx.ConnPool {
 	config := pgx.ConnPoolConfig{ConnConfig: *defaultConnConfig, MaxConnections: maxConnections}
+	config.MaxConnLifetime = 250 * time.Millisecond
 	pool, err := pgx.NewConnPool(config)
 	if err != nil {
 		t.Fatalf("Unable to create connection pool: %v", err)
@@ -150,6 +151,32 @@ func TestPoolAcquireAndReleaseCycle(t *testing.T) {
 	releaseAllConnections(pool, allConnections)
 }
 
+func TestPoolReleaseChecksMaxConnLifetime(t *testing.T) {
+	t.Parallel()
+
+	config := pgx.ConnPoolConfig{ConnConfig: *defaultConnConfig}
+	pool, err := pgx.NewConnPool(config)
+	if err != nil {
+		t.Fatal("Unable to establish connection pool")
+	}
+	defer pool.Close()
+
+	c, err := pool.Acquire()
+	if err != nil {
+		t.Fatal("Unable to acquire connection from the pool")
+	}
+
+	time.Sleep(config.MaxConnLifetime)
+
+	pool.Release(c)
+	waitForReleaseToComplete()
+
+	stats := pool.Stat()
+	if stats.CurrentConnections != 0 && stats.AvailableConnections != 0 {
+		t.Fatal("Unable to recycle connection from the pool")
+	}
+}
+
 func TestPoolNonBlockingConnections(t *testing.T) {
 	t.Parallel()
 
@@ -1227,3 +1254,10 @@ func TestConnPoolBeginEx(t *testing.T) {
 		t.Fatal("Should not be able to create a tx")
 	}
 }
+
+// Conn.Release is an asynchronous process that returns immediately. There is no signal when the actual work is
+// completed. To test something that relies on the actual work for Conn.Release being completed we must simply wait.
+// This function wraps the sleep so there is more meaning for the callers.
+func waitForReleaseToComplete() {
+	time.Sleep(5 * time.Millisecond)
+}