domain: support retry if load failed.

domain/domain.go

@@ -142,45 +142,59 @@ func (do *Domain) tryReload() {
 	}
 }
 
+const minReloadTimeout = 20 * time.Second
+
 func (do *Domain) reload() error {
 	// lock here for only once at same time.
 	do.m.Lock()
 	defer do.m.Unlock()
 
-	err := kv.RunInNewTxn(do.store, false, do.loadInfoSchema)
-	if err != nil {
-		return errors.Trace(err)
+	timeout := do.ddl.GetLease() / 2
+	if timeout < minReloadTimeout {
+		timeout = minReloadTimeout
 	}
 
-	atomic.StoreInt64(&do.lastLeaseTS, time.Now().UnixNano())
-	return nil
+	done := make(chan error, 1)
+	go func() {
+		var err error
+
+		for {
+			err = kv.RunInNewTxn(do.store, false, do.loadInfoSchema)
+			// if err is db closed, we will return it directly, otherwise, we will
+			// check reloading again.
+			if terror.ErrorEqual(err, localstore.ErrDBClosed) {
+				break
+			}
+
+			if err != nil {
+				// TODO: use a backoff algorithm.
+				time.Sleep(500 * time.Millisecond)
+				continue
+			}
+
+			atomic.StoreInt64(&do.lastLeaseTS, time.Now().UnixNano())
+			break
+		}
+
+		done <- err
+	}()
+
+	select {
+	case err := <-done:
+		return errors.Trace(err)
+	case <-time.After(timeout):
+		return errors.Errorf("reload schema timeout")
+	}
 }
 
 func (do *Domain) mustReload() {
 	// if reload error, we will terminate whole program to guarantee data safe.
-	// TODO: retry some times if reload error.
 	err := do.reload()
 	if err != nil {
-		log.Fatalf("reload schema err %v", err)
+		log.Fatalf("reload schema err %v", errors.ErrorStack(err))
 	}
 }
 
-const maxReloadTimeout = 60 * time.Second
-const minReloadTimeout = 20 * time.Second
-
-func getReloadTimeout(lease time.Duration) time.Duration {
-	timeout := lease / 4
-
-	if timeout >= maxReloadTimeout {
-		return maxReloadTimeout
-	}
-	if timeout <= minReloadTimeout {
-		return minReloadTimeout
-	}
-
-	return timeout
-}
-
 // check schema every 300 seconds default.
 const defaultLoadTime = 300 * time.Second
 
@@ -192,26 +206,16 @@ func (do *Domain) loadSchemaInLoop(lease time.Duration) {
 	ticker := time.NewTicker(lease)
 	defer ticker.Stop()
 
-	reloadTimeout := getReloadTimeout(lease)
-	reloadErrCh := make(chan error, 1)
-
 	for {
 		select {
 		case <-ticker.C:
-			go func() {
-				reloadErrCh <- do.reload()
-			}()
-			select {
-			case err := <-reloadErrCh:
-				// we may close store in test, but the domain load schema loop is still checking,
-				// so we can't panic for ErrDBClosed and just return here.
-				if terror.ErrorEqual(err, localstore.ErrDBClosed) {
-					return
-				} else if err != nil {
-					log.Fatalf("reload schema err %v", errors.ErrorStack(err))
-				}
-			case <-time.After(reloadTimeout):
-				log.Fatalf("reload schema timeout:%d", reloadTimeout)
+			err := do.reload()
+			// we may close store in test, but the domain load schema loop is still checking,
+			// so we can't panic for ErrDBClosed and just return here.
+			if terror.ErrorEqual(err, localstore.ErrDBClosed) {
+				return
+			} else if err != nil {
+				log.Fatalf("reload schema err %v", errors.ErrorStack(err))
 			}
 		case newLease := <-do.leaseCh:
 			if newLease <= 0 {
@@ -224,7 +228,6 @@ func (do *Domain) loadSchemaInLoop(lease time.Duration) {
 			}
 
 			lease = newLease
-			reloadTimeout = getReloadTimeout(lease)
 			// reset ticker too.
 			ticker.Stop()
 			ticker = time.NewTicker(lease)

domain/domain_test.go

@@ -14,11 +14,13 @@
 package domain
 
 import (
+	"sync/atomic"
 	"testing"
 	"time"
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/tidb/model"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/store/localstore"
 	"github.com/pingcap/tidb/store/localstore/goleveldb"
 	"github.com/pingcap/tidb/util/mock"
@@ -59,16 +61,13 @@ func (*testSuite) TestT(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(m[ddlLastReloadSchemaTS], GreaterEqual, int64(0))
 
-	dom.SetLease(50 * time.Millisecond)
+	c.Assert(dom.GetScope("dummy_status"), Equals, variable.DefaultScopeFlag)
+
+	dom.SetLease(10 * time.Millisecond)
+	time.Sleep(20 * time.Millisecond)
+	atomic.StoreInt64(&dom.lastLeaseTS, 0)
+	dom.tryReload()
+
 	store.Close()
 	time.Sleep(1 * time.Second)
 }
-
-func (*testSuite) TestGetReloadTimeout(c *C) {
-	timeout := getReloadTimeout(241 * time.Second)
-	c.Assert(timeout, Equals, maxReloadTimeout)
-	timeout = getReloadTimeout(76 * time.Second)
-	c.Assert(timeout, Equals, minReloadTimeout)
-	timeout = getReloadTimeout(120 * time.Second)
-	c.Assert(timeout, Equals, 30*time.Second)
-}