Add pool MaxConnLifetime

pool/conn.go

@@ -2,6 +2,7 @@ package pool
 
 import (
 	"context"
+	"time"
 
 	"github.com/jackc/pgconn"
 	"github.com/jackc/pgx/v4"
@@ -26,7 +27,8 @@ func (c *Conn) Release() {
 	c.res = nil
 
 	go func() {
-		if !conn.IsAlive() || conn.PgConn().TxStatus != 'I' {
+		now := time.Now()
+		if !conn.IsAlive() || conn.PgConn().TxStatus != 'I' || (now.Sub(res.CreationTime()) > c.p.maxConnLifetime) {
 			res.Destroy()
 			return
 		}

pool/pool.go

@@ -2,7 +2,6 @@ package pool
 
 import (
 	"context"
-	"fmt"
 	"runtime"
 	"strconv"
 	"time"
@@ -10,14 +9,20 @@ import (
 	"github.com/jackc/pgconn"
 	"github.com/jackc/pgx/v4"
 	"github.com/jackc/puddle"
+	errors "golang.org/x/xerrors"
 )
 
-const defaultMaxConns = 5
+var defaultMinMaxConns = int32(4)
+var defaultMaxConnLifetime = time.Hour
+var defaultHealthCheckPeriod = time.Minute
 
 type Pool struct {
-	p             *puddle.Pool
-	beforeAcquire func(*pgx.Conn) bool
-	afterRelease  func(*pgx.Conn) bool
+	p                 *puddle.Pool
+	beforeAcquire     func(*pgx.Conn) bool
+	afterRelease      func(*pgx.Conn) bool
+	maxConnLifetime   time.Duration
+	healthCheckPeriod time.Duration
+	closeChan         chan struct{}
 }
 
 type Config struct {
@@ -32,7 +37,14 @@ type Config struct {
 	// return the connection to the pool or false to destroy the connection.
 	AfterRelease func(*pgx.Conn) bool
 
+	// MaxConnLifetime is the duration after which a connection will be automatically closed.
+	MaxConnLifetime time.Duration
+
+	// MaxConns is the maximum size of the pool.
 	MaxConns int32
+
+	// HealthCheckPeriod is the duration between checks of the health of idle connections.
+	HealthCheckPeriod time.Duration
 }
 
 // Connect creates a new Pool and immediately establishes one connection. ctx can be used to cancel this initial
@@ -50,8 +62,11 @@ func Connect(ctx context.Context, connString string) (*Pool, error) {
 // connection.
 func ConnectConfig(ctx context.Context, config *Config) (*Pool, error) {
 	p := &Pool{
-		beforeAcquire: config.BeforeAcquire,
-		afterRelease:  config.AfterRelease,
+		beforeAcquire:     config.BeforeAcquire,
+		afterRelease:      config.AfterRelease,
+		maxConnLifetime:   config.MaxConnLifetime,
+		healthCheckPeriod: config.HealthCheckPeriod,
+		closeChan:         make(chan struct{}),
 	}
 
 	p.p = puddle.NewPool(
@@ -64,6 +79,8 @@ func ConnectConfig(ctx context.Context, config *Config) (*Pool, error) {
 		config.MaxConns,
 	)
 
+	go p.backgroundHealthCheck()
+
 	// Initially establish one connection
 	res, err := p.p.Acquire(ctx)
 	if err != nil {
@@ -87,25 +104,78 @@ func ParseConfig(connString string) (*Config, error) {
 		delete(connConfig.Config.RuntimeParams, "pool_max_conns")
 		n, err := strconv.ParseInt(s, 10, 32)
 		if err != nil {
-			return nil, fmt.Errorf("invalid pool_max_conns: %v", err)
+			return nil, errors.Errorf("cannot parse pool_max_conns: %w", err)
+		}
+		if n < 1 {
+			return nil, errors.Errorf("pool_max_conns too small: %d", n)
 		}
 		config.MaxConns = int32(n)
 	} else {
-		config.MaxConns = 4
-		if int32(runtime.NumCPU()) > config.MaxConns {
-			config.MaxConns = runtime.NumCPU()
+		config.MaxConns = defaultMinMaxConns
+		if numCPU := int32(runtime.NumCPU()); numCPU > config.MaxConns {
+			config.MaxConns = numCPU
 		}
 	}
 
+	if s, ok := config.ConnConfig.Config.RuntimeParams["pool_max_conn_lifetime"]; ok {
+		delete(connConfig.Config.RuntimeParams, "pool_max_conn_lifetime")
+		d, err := time.ParseDuration(s)
+		if err != nil {
+			return nil, errors.Errorf("invalid pool_max_conn_lifetime: %w", err)
+		}
+		config.MaxConnLifetime = d
+	} else {
+		config.MaxConnLifetime = defaultMaxConnLifetime
+	}
+
+	if s, ok := config.ConnConfig.Config.RuntimeParams["pool_health_check_period"]; ok {
+		delete(connConfig.Config.RuntimeParams, "pool_health_check_period")
+		d, err := time.ParseDuration(s)
+		if err != nil {
+			return nil, errors.Errorf("invalid pool_health_check_period: %w", err)
+		}
+		config.HealthCheckPeriod = d
+	} else {
+		config.HealthCheckPeriod = defaultHealthCheckPeriod
+	}
+
 	return config, nil
 }
 
 // Close closes all connections in the pool and rejects future Acquire calls. Blocks until all connections are returned
 // to pool and closed.
 func (p *Pool) Close() {
+	close(p.closeChan)
 	p.p.Close()
 }
 
+func (p *Pool) backgroundHealthCheck() {
+	ticker := time.NewTicker(p.healthCheckPeriod)
+
+	for {
+		select {
+		case <-p.closeChan:
+			ticker.Stop()
+			return
+		case <-ticker.C:
+			p.checkIdleConnsHealth()
+		}
+	}
+}
+
+func (p *Pool) checkIdleConnsHealth() {
+	resources := p.p.AcquireAllIdle()
+
+	now := time.Now()
+	for _, res := range resources {
+		if now.Sub(res.CreationTime()) > p.maxConnLifetime {
+			res.Destroy()
+		} else {
+			res.Release()
+		}
+	}
+}
+
 func (p *Pool) Acquire(ctx context.Context) (*Conn, error) {
 	for {
 		res, err := p.p.Acquire(ctx)

pool/pool_test.go

@@ -158,6 +158,50 @@ func TestPoolAcquireAllIdle(t *testing.T) {
 	}
 }
 
+func TestConnReleaseChecksMaxConnLifetime(t *testing.T) {
+	t.Parallel()
+
+	config, err := pool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(t, err)
+
+	config.MaxConnLifetime = 250 * time.Millisecond
+
+	db, err := pool.ConnectConfig(context.Background(), config)
+	defer db.Close()
+
+	c, err := db.Acquire(context.Background())
+	require.NoError(t, err)
+
+	time.Sleep(config.MaxConnLifetime)
+
+	c.Release()
+	waitForReleaseToComplete()
+
+	stats := db.Stat()
+	assert.EqualValues(t, 0, stats.TotalConns())
+}
+
+func TestPoolBackgroundChecksMaxConnLifetime(t *testing.T) {
+	t.Parallel()
+
+	config, err := pool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(t, err)
+
+	config.MaxConnLifetime = 100 * time.Millisecond
+	config.HealthCheckPeriod = 100 * time.Millisecond
+
+	db, err := pool.ConnectConfig(context.Background(), config)
+	defer db.Close()
+
+	c, err := db.Acquire(context.Background())
+	require.NoError(t, err)
+	c.Release()
+	time.Sleep(config.MaxConnLifetime + 50*time.Millisecond)
+
+	stats := db.Stat()
+	assert.EqualValues(t, 0, stats.TotalConns())
+}
+
 func TestPoolExec(t *testing.T) {
 	t.Parallel()