feat(chpool): add healthcheck function

Author: Neven Miculinic

chpool/client.go

@@ -2,7 +2,6 @@ package chpool
 
 import (
 	"context"
-	"time"
 
 	"github.com/jackc/puddle/v2"
 
@@ -21,14 +20,16 @@ func (c *Client) Release() {
 		return
 	}
 
-	client := c.client()
-
-	if client.IsClosed() || time.Since(c.res.CreationTime()) > c.p.options.MaxConnLifetime {
-		c.res.Destroy()
-		return
-	}
-
-	c.res.Release()
+	// calling async since connIsHealthy may block
+	go func() {
+		if c.p.connIsHealthy(c.res) {
+			c.p.options.ClientOptions.Logger.Debug("chpool: releasing connection")
+			c.res.Release()
+		} else {
+			c.p.options.ClientOptions.Logger.Debug("chpool: destoying connection")
+			c.res.Destroy()
+		}
+	}()
 }
 
 func (c *Client) Do(ctx context.Context, q ch.Query) (err error) {

chpool/client_test.go

@@ -2,9 +2,13 @@ package chpool
 
 import (
 	"context"
+	"sync/atomic"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/ClickHouse/ch-go"
 )
 
 func TestClient_Do(t *testing.T) {
@@ -17,6 +21,24 @@ func TestClient_Do(t *testing.T) {
 	testDo(t, conn)
 }
 
+func TestClient_ReleaseHealthCheck(t *testing.T) {
+	t.Parallel()
+	var healthCheckCnt int64
+	p := PoolConnOpt(t, Options{
+		HealthCheckFunc: func(ctx context.Context, client *ch.Client) error {
+			atomic.AddInt64(&healthCheckCnt, 1)
+			return nil
+		},
+	})
+	conn, err := p.Acquire(context.Background())
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), atomic.LoadInt64(&healthCheckCnt))
+
+	conn.Release()
+	waitForReleaseToComplete()
+	assert.Equal(t, int64(1), atomic.LoadInt64(&healthCheckCnt))
+}
+
 func TestClient_Ping(t *testing.T) {
 	t.Parallel()
 	p := PoolConn(t)

chpool/conn.go

@@ -1,14 +1,17 @@
 package chpool
 
 import (
+	"time"
+
 	"github.com/jackc/puddle/v2"
 
 	"github.com/ClickHouse/ch-go"
 )
 
 type connResource struct {
-	client  *ch.Client
-	clients []Client
+	lastHealthCheckTimestamp time.Time
+	client                   *ch.Client
+	clients                  []Client
 }
 
 func (cr *connResource) getConn(p *Pool, res *puddle.Resource[*connResource]) *Client {

chpool/pool.go

@@ -6,9 +6,10 @@ import (
 	"sync"
 	"time"
 
-	"github.com/ClickHouse/ch-go"
-
 	"github.com/jackc/puddle/v2"
+	"go.uber.org/zap"
+
+	"github.com/ClickHouse/ch-go"
 )
 
 // Pool of connections to ClickHouse.
@@ -23,19 +24,26 @@ type Pool struct {
 
 // Options for Pool.
 type Options struct {
-	ClientOptions     ch.Options
-	MaxConnLifetime   time.Duration
-	MaxConnIdleTime   time.Duration
-	MaxConns          int32
-	MinConns          int32
-	HealthCheckPeriod time.Duration
+	ClientOptions      ch.Options
+	MaxConnLifetime    time.Duration
+	MaxConnIdleTime    time.Duration
+	MaxConns           int32
+	MinConns           int32
+	HealthCheckPeriod  time.Duration
+	HealthCheckFunc    func(ctx context.Context, client *ch.Client) error
+	HealthCheckTimeout time.Duration
+}
+
+func DefaultHealthCheckFunc(ctx context.Context, client *ch.Client) error {
+	return client.Ping(ctx)
 }
 
 // Defaults for pool.
 const (
-	DefaultMaxConnLifetime   = time.Hour
-	DefaultMaxConnIdleTime   = time.Minute * 30
-	DefaultHealthCheckPeriod = time.Minute
+	DefaultMaxConnLifetime    = time.Hour
+	DefaultMaxConnIdleTime    = time.Minute * 30
+	DefaultHealthCheckPeriod  = time.Minute
+	DefaultHealthCheckTimeout = time.Second
 )
 
 func (o *Options) setDefaults() {
@@ -51,6 +59,15 @@ func (o *Options) setDefaults() {
 	if o.HealthCheckPeriod == 0 {
 		o.HealthCheckPeriod = DefaultHealthCheckPeriod
 	}
+	if o.HealthCheckFunc == nil {
+		o.HealthCheckFunc = DefaultHealthCheckFunc
+	}
+	if o.HealthCheckTimeout == 0 {
+		o.HealthCheckTimeout = DefaultHealthCheckTimeout
+	}
+	if o.ClientOptions.Logger == nil {
+		o.ClientOptions.Logger = zap.NewNop()
+	}
 }
 
 // Dial returns a pool of connections to ClickHouse.
@@ -162,16 +179,47 @@ func (p *Pool) backgroundHealthCheck() {
 func (p *Pool) checkIdleConnsHealth() {
 	resources := p.pool.AcquireAllIdle()
 
-	now := time.Now()
+	wg := sync.WaitGroup{}
 	for _, res := range resources {
-		if now.Sub(res.CreationTime()) > p.options.MaxConnLifetime {
-			res.Destroy()
-		} else if res.IdleDuration() > p.options.MaxConnIdleTime {
-			res.Destroy()
-		} else {
-			res.ReleaseUnused()
+		res := res
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if res.IdleDuration() > p.options.MaxConnIdleTime || !p.connIsHealthy(res) {
+				res.Destroy()
+			} else {
+				res.ReleaseUnused()
+			}
+		}()
+		wg.Wait()
+	}
+}
+
+func (p *Pool) connIsHealthy(res *puddle.Resource[*connResource]) bool {
+	logger := p.options.ClientOptions.Logger
+	if res.Value().client.IsClosed() {
+		logger.Debug("chpool: connection is closed")
+		return false
+	}
+
+	if time.Since(res.CreationTime()) > p.options.MaxConnLifetime {
+		logger.Debug("chpool: connection over max lifetime")
+		return false
+	}
+
+	if p.options.HealthCheckFunc != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), p.options.HealthCheckTimeout)
+		defer cancel()
+		if err := p.options.HealthCheckFunc(ctx, res.Value().client); err != nil {
+			if logger := p.options.ClientOptions.Logger; logger != nil {
+				logger.Warn("chpool: health check failed", zap.Error(err))
+			}
+			return false
 		}
 	}
+
+	res.Value().lastHealthCheckTimestamp = time.Now()
+	return true
 }
 
 func (p *Pool) checkMinConns() {

chpool/pool_test.go

@@ -2,9 +2,12 @@ package chpool
 
 import (
 	"context"
+	"sync/atomic"
 	"testing"
 	"time"
 
+	"github.com/ClickHouse/ch-go"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -61,6 +64,7 @@ func TestPool_Ping(t *testing.T) {
 	p := PoolConn(t)
 
 	require.NoError(t, p.Ping(context.Background()))
+	waitForReleaseToComplete()
 
 	stats := p.Stat()
 	assert.EqualValues(t, 0, stats.AcquiredResources())
@@ -78,3 +82,23 @@ func TestPool_Acquire(t *testing.T) {
 	waitForReleaseToComplete()
 	require.EqualValues(t, 2, p.Stat().AcquireCount())
 }
+
+func TestPool_backgroundHealthCheck(t *testing.T) {
+	t.Parallel()
+	var healthCheckCnt int64
+	p := PoolConnOpt(t, Options{
+		MinConns: 1,
+		HealthCheckFunc: func(ctx context.Context, client *ch.Client) error {
+			atomic.AddInt64(&healthCheckCnt, 1)
+			return nil
+		},
+		HealthCheckPeriod: 500 * time.Millisecond,
+	})
+	p.checkMinConns()
+	p.checkIdleConnsHealth()
+	assert.GreaterOrEqual(t, int64(1), atomic.LoadInt64(&healthCheckCnt))
+
+	hc := atomic.LoadInt64(&healthCheckCnt)
+	time.Sleep(750 * time.Millisecond)
+	assert.Equal(t, hc+1, atomic.LoadInt64(&healthCheckCnt))
+}