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sql: fix recent racy regression #93360

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merged 1 commit into from
Dec 12, 2022
Merged

sql: fix recent racy regression #93360

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51 changes: 33 additions & 18 deletions pkg/sql/distsql_running.go
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Original file line number Diff line number Diff line change
Expand Up @@ -587,9 +587,9 @@ func (dsp *DistSQLPlanner) setupFlows(
//
// In order to not protect DistSQLReceiver.status with a mutex,
// we do not update the status here and, instead, rely on the
// DistSQLReceiver detecting the error the next time a meta is
// pushed into it.
recv.setErrorWithoutStatusUpdate(res.err)
// DistSQLReceiver detecting the error the next time an object
// is pushed into it.
recv.setErrorWithoutStatusUpdate(res.err, true /* willDeferStatusUpdate */)
// Now explicitly cancel the local flow.
flow.Cancel()
}
Expand Down Expand Up @@ -834,6 +834,11 @@ type DistSQLReceiver struct {
row rowResultWriter
batch batchResultWriter
}
// updateStatus, if true, indicates that a concurrent goroutine has set an
// error on the rowResultWriter without updating status, so the main
// goroutine needs to update the status.
updateStatus atomic.Bool
status execinfra.ConsumerStatus

stmtType tree.StatementReturnType

Expand All @@ -859,7 +864,6 @@ type DistSQLReceiver struct {
commErr error

row tree.Datums
status execinfra.ConsumerStatus
alloc tree.DatumAlloc
closed bool

Expand Down Expand Up @@ -1174,12 +1178,12 @@ func (r *DistSQLReceiver) getError() error {
}

// setErrorWithoutStatusUpdate sets the error in the rowResultWriter but does
// **not** update the status of the DistSQLReceiver. The status will be updated
// the next time a meta is pushed into the receiver (by the goroutine that is
// pushing).
// **not** update the status of the DistSQLReceiver. willDeferStatusUpdate
// indicates whether the main goroutine should update the status the next time
// it pushes something into the DistSQLReceiver.
//
// NOTE: consider using SetError() instead.
func (r *DistSQLReceiver) setErrorWithoutStatusUpdate(err error) {
func (r *DistSQLReceiver) setErrorWithoutStatusUpdate(err error, willDeferStatusUpdate bool) {
r.resultWriterMu.Lock()
defer r.resultWriterMu.Unlock()
// Check if the error we just received should take precedence over a
Expand All @@ -1204,6 +1208,7 @@ func (r *DistSQLReceiver) setErrorWithoutStatusUpdate(err error) {
}
}
r.resultWriterMu.row.SetError(err)
r.updateStatus.Store(willDeferStatusUpdate)
}
}

Expand All @@ -1227,20 +1232,28 @@ func (r *DistSQLReceiver) updateStatusAfterError(err error) {
//
// The status of DistSQLReceiver is updated accordingly.
func (r *DistSQLReceiver) SetError(err error) {
r.setErrorWithoutStatusUpdate(err)
r.setErrorWithoutStatusUpdate(err, false /* willDeferStatusUpdate */)
r.updateStatusAfterError(err)
}

// checkConcurrentError sets the status if an error has been set by another
// goroutine that did not also update the status.
func (r *DistSQLReceiver) checkConcurrentError() {
if r.status != execinfra.NeedMoreRows || !r.updateStatus.Load() {
// If the status already is not NeedMoreRows, then it doesn't matter if
// there was a concurrent error set.
return
}
previousErr := r.getError()
if previousErr == nil {
previousErr = errors.AssertionFailedf("unexpectedly updateStatus is set but there is no error")
}
r.updateStatusAfterError(previousErr)
}

// pushMeta takes in non-empty metadata object and pushes it to the result
// writer. Possibly updated status is returned.
func (r *DistSQLReceiver) pushMeta(meta *execinfrapb.ProducerMetadata) execinfra.ConsumerStatus {
// Check whether an error has been set by another goroutine without updating
// the status.
if r.status == execinfra.NeedMoreRows {
if previousErr := r.getError(); previousErr != nil {
r.updateStatusAfterError(previousErr)
}
}
if metaWriter, ok := r.resultWriterMu.row.(MetadataResultWriter); ok {
metaWriter.AddMeta(r.ctx, meta)
}
Expand Down Expand Up @@ -1346,13 +1359,14 @@ func (r *DistSQLReceiver) handleCommErr(commErr error) {
func (r *DistSQLReceiver) Push(
row rowenc.EncDatumRow, meta *execinfrapb.ProducerMetadata,
) execinfra.ConsumerStatus {
r.checkConcurrentError()
if r.testingKnobs.pushCallback != nil {
r.testingKnobs.pushCallback(row, meta)
}
if meta != nil {
return r.pushMeta(meta)
}
if r.ctx.Err() != nil && r.getError() == nil {
if r.ctx.Err() != nil && r.status != execinfra.ConsumerClosed {
r.SetError(r.ctx.Err())
}
if r.status != execinfra.NeedMoreRows {
Expand Down Expand Up @@ -1425,10 +1439,11 @@ func (r *DistSQLReceiver) Push(
func (r *DistSQLReceiver) PushBatch(
batch coldata.Batch, meta *execinfrapb.ProducerMetadata,
) execinfra.ConsumerStatus {
r.checkConcurrentError()
if meta != nil {
return r.pushMeta(meta)
}
if r.ctx.Err() != nil && r.getError() == nil {
if r.ctx.Err() != nil && r.status != execinfra.ConsumerClosed {
r.SetError(r.ctx.Err())
}
if r.status != execinfra.NeedMoreRows {
Expand Down