From e04723a56fe84785145e1e88eb3befcacaf3b86f Mon Sep 17 00:00:00 2001
From: crazycs <crazycs520@gmail.com>
Date: Tue, 2 Jul 2019 11:44:14 +0800
Subject: [PATCH] ddl: add recover for run ddl job (#10981) (#11022)

---
 ddl/ddl_worker.go            | 14 +++++++++++++-
 ddl/failtest/fail_db_test.go | 14 ++++++++++++++
 ddl/table.go                 |  2 +-
 infoschema/infoschema.go     |  5 +++++
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/ddl/ddl_worker.go b/ddl/ddl_worker.go
index 2151d9efebb78..6ec289f3ebd82 100644
--- a/ddl/ddl_worker.go
+++ b/ddl/ddl_worker.go
@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/parser/terror"
 	"github.com/pingcap/tidb/ddl/util"
@@ -30,6 +31,7 @@ import (
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/sessionctx/binloginfo"
 	"github.com/pingcap/tidb/sessionctx/variable"
+	tidbutil "github.com/pingcap/tidb/util"
 	"github.com/pingcap/tidb/util/admin"
 	"github.com/pingcap/tidb/util/logutil"
 	"go.uber.org/zap"
@@ -397,7 +399,14 @@ func (w *worker) handleDDLJobQueue(d *ddlCtx) error {
 
 			// If running job meets error, we will save this error in job Error
 			// and retry later if the job is not cancelled.
-			schemaVer, runJobErr = w.runDDLJob(d, t, job)
+			tidbutil.WithRecovery(func() {
+				schemaVer, runJobErr = w.runDDLJob(d, t, job)
+			}, func(r interface{}) {
+				if r != nil {
+					// If run ddl job panic, just cancel the ddl jobs.
+					job.State = model.JobStateCancelling
+				}
+			})
 			if job.IsCancelled() {
 				txn.Reset()
 				err = w.finishDDLJob(t, job)
@@ -469,6 +478,9 @@ func chooseLeaseTime(t, max time.Duration) time.Duration {
 
 // runDDLJob runs a DDL job. It returns the current schema version in this transaction and the error.
 func (w *worker) runDDLJob(d *ddlCtx, t *meta.Meta, job *model.Job) (ver int64, err error) {
+	// Mock for run ddl job panic.
+	failpoint.Inject("mockPanicInRunDDLJob", func(_ failpoint.Value) {})
+
 	logutil.Logger(w.logCtx).Info("[ddl] run DDL job", zap.String("job", job.String()))
 	timeStart := time.Now()
 	defer func() {
diff --git a/ddl/failtest/fail_db_test.go b/ddl/failtest/fail_db_test.go
index a8ad59c218ed0..8488cda6cddf7 100644
--- a/ddl/failtest/fail_db_test.go
+++ b/ddl/failtest/fail_db_test.go
@@ -386,3 +386,17 @@ LOOP:
 	tk.MustExec("admin check table test_add_index")
 	tk.MustExec("drop table test_add_index")
 }
+
+// TestRunDDLJobPanic tests recover panic when run ddl job panic.
+func (s *testFailDBSuite) TestRunDDLJobPanic(c *C) {
+	defer func() {
+		c.Assert(failpoint.Disable("github.com/pingcap/tidb/ddl/mockPanicInRunDDLJob"), IsNil)
+	}()
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	c.Assert(failpoint.Enable("github.com/pingcap/tidb/ddl/mockPanicInRunDDLJob", `1*panic("panic test")`), IsNil)
+	_, err := tk.Exec("create table t(c1 int, c2 int)")
+	c.Assert(err, NotNil)
+	c.Assert(err.Error(), Equals, "[ddl:12]cancelled DDL job")
+}
diff --git a/ddl/table.go b/ddl/table.go
index a466f40e2f2af..3232fa3ab8ae2 100644
--- a/ddl/table.go
+++ b/ddl/table.go
@@ -765,7 +765,7 @@ func onModifyTableCharsetAndCollate(t *meta.Meta, job *model.Job) (ver int64, _
 
 func checkTableNotExists(d *ddlCtx, t *meta.Meta, schemaID int64, tableName string) error {
 	// d.infoHandle maybe nil in some test.
-	if d.infoHandle == nil {
+	if d.infoHandle == nil || !d.infoHandle.IsValid() {
 		return checkTableNotExistsFromStore(t, schemaID, tableName)
 	}
 	// Try to use memory schema info to check first.
diff --git a/infoschema/infoschema.go b/infoschema/infoschema.go
index ed455b3dacfcb..7b0b5f612cae0 100644
--- a/infoschema/infoschema.go
+++ b/infoschema/infoschema.go
@@ -292,6 +292,11 @@ func (h *Handle) Get() InfoSchema {
 	return schema
 }
 
+// IsValid uses to check whether handle value is valid.
+func (h *Handle) IsValid() bool {
+	return h.value.Load() != nil
+}
+
 // EmptyClone creates a new Handle with the same store and memSchema, but the value is not set.
 func (h *Handle) EmptyClone() *Handle {
 	newHandle := &Handle{