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worker: fix potential panic when restoring subtask from meta #305

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Oct 16, 2019
Merged

worker: fix potential panic when restoring subtask from meta #305

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e14e0b9
worker: fix potential panic when restoring subtask from meta
csuzhangxc Oct 8, 2019
a8c2e6a
Update dm/worker/worker.go
csuzhangxc Oct 14, 2019
713b989
Merge branch 'master' into fix-worker-ctx-panic
csuzhangxc Oct 14, 2019
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51 changes: 33 additions & 18 deletions dm/worker/worker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,14 +71,29 @@ type Worker struct {
}

// NewWorker creates a new Worker
func NewWorker(cfg *Config) (*Worker, error) {
w := &Worker{
func NewWorker(cfg *Config) (w *Worker, err error) {
w = &Worker{
cfg: cfg,
relayHolder: NewRelayHolder(cfg),
tracer: tracing.InitTracerHub(cfg.Tracer),
subTaskHolder: newSubTaskHolder(),
l: log.With(zap.String("component", "worker controller")),
}
w.ctx, w.cancel = context.WithCancel(context.Background())

defer func(w2 *Worker) {
if err != nil { // when err !=nil, `w` will become nil in this func, so we pass `w` in defer.
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// release resources, NOTE: we need to refactor New/Init/Start/Close for components later.
w2.cancel()
w2.subTaskHolder.closeAllSubTasks()
if w2.meta != nil {
w2.meta.Close()
}
if w2.db != nil {
w2.db.Close()
}
Comment on lines +86 to +94
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can we just use w2.Close(), and maybe need add some check in Close (close something when it is not nil)

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I think we can.
But I also think we should refactor the pattern of components' new/init/start/close later.
like new only creates fields but does not acquire (IO) resources and start no goroutines, then when new failed, no operation needs to do and let GC to remove the objects is enough.

I think we need to do some refactoring when developing the HA version of DM.

what's your opinion?

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OK，we can do this later

}
}(w)

// initial relay holder
purger, err := w.relayHolder.Init([]purger.PurgeInterceptor{
Expand Down Expand Up @@ -107,16 +122,18 @@ func NewWorker(cfg *Config) (*Worker, error) {
}

// open kv db
w.db, err = openDB(dbDir, defaultKVConfig)
metaDB, err := openDB(dbDir, defaultKVConfig)
if err != nil {
return nil, err
}
w.db = metaDB

// initial metadata
w.meta, err = NewMetadata(dbDir, w.db)
meta, err := NewMetadata(dbDir, w.db)
if err != nil {
return nil, err
}
w.meta = meta

InitConditionHub(w)

Expand All @@ -125,6 +142,18 @@ func NewWorker(cfg *Config) (*Worker, error) {
return nil, err
}

w.l.Info("initialized")

return w, nil
}

// Start starts working
func (w *Worker) Start() {
if w.closed.Get() == closedTrue {
w.l.Warn("already closed")
return
}

// start relay
w.relayHolder.Start()

Expand All @@ -141,20 +170,6 @@ func NewWorker(cfg *Config) (*Worker, error) {
w.tracer.Start()
}

w.ctx, w.cancel = context.WithCancel(context.Background())

w.l.Info("initialzed")

return w, nil
}

// Start starts working
func (w *Worker) Start() {
if w.closed.Get() == closedTrue {
w.l.Warn("already closed")
return
}

w.wg.Add(2)
defer w.wg.Done()

Expand Down
6 changes: 3 additions & 3 deletions dm/worker/worker_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ func (t *testServer) testWorkerHandleTask(c *C) {
w.handleTask()
}()

c.Assert(utils.WaitSomething(5, 10*time.Millisecond, func() bool {
c.Assert(utils.WaitSomething(10, 100*time.Millisecond, func() bool {
w.meta.Lock()
defer w.meta.Unlock()
return len(w.meta.logs) == 0
Expand Down Expand Up @@ -154,7 +154,7 @@ func (t *testServer) TestTaskAutoResume(c *C) {
defer s.Close()
c.Assert(s.Start(), IsNil)
}()
c.Assert(utils.WaitSomething(30, 10*time.Millisecond, func() bool {
c.Assert(utils.WaitSomething(10, 100*time.Millisecond, func() bool {
return !s.closed.Get()
}), IsTrue)

Expand All @@ -165,7 +165,7 @@ func (t *testServer) TestTaskAutoResume(c *C) {
c.Assert(err, IsNil)

// check task in paused state
c.Assert(utils.WaitSomething(10, 10*time.Millisecond, func() bool {
c.Assert(utils.WaitSomething(10, 100*time.Millisecond, func() bool {
for _, st := range s.worker.QueryStatus(taskName) {
if st.Name == taskName && st.Stage == pb.Stage_Paused {
return true
Expand Down