exempt WIP

Author: RaduBerinde

db.go

@@ -1114,8 +1114,8 @@ func (d *DB) newIter(
 		dbi.batch.batch = batch
 		dbi.batch.batchSeqNum = batch.nextSeqNum()
 	}
-	if !dbi.batchOnlyIter && d.iterTracker != nil {
-		dbi.tracker = d.iterTracker
+	dbi.tracker = d.iterTracker
+	if !dbi.batchOnlyIter && d.iterTracker != nil && !dbi.opts.ExemptFromTracking {
 		dbi.trackerHandle = d.iterTracker.Start()
 	}
 	return finishInitializingIter(ctx, buf)

internal/inflight/in_flight.go

@@ -72,6 +72,10 @@ type Tracker struct {
 // A zero Handle is not valid.
 type Handle uint64
 
+func (h Handle) IsValid() bool {
+	return h != 0
+}
+
 // ReportFn is called (typically periodically) with a formatted report that
 // describes entries older than some threshold. An empty string report is never
 // delivered by the polling tracker.

iterator.go

@@ -210,7 +210,9 @@ type Iterator struct {
 	// short-lived (since they pin memtables and sstables), (b) plumbing a
 	// context into every method is very painful, (c) they do not (yet) respect
 	// context cancellation and are only used for tracing.
-	ctx           context.Context
+	ctx context.Context
+	// TODO(radu): group fields that are always set from `db` fields (tracker,
+	// merge, comparer, fc) into a single struct we can point to.
 	tracker       *inflight.Tracker
 	trackerHandle inflight.Handle
 	opts          IterOptions
@@ -2365,8 +2367,9 @@ const maxKeyBufCacheSize = 4 << 10 // 4 KB
 // It is not valid to call any method, including Close, after the iterator
 // has been closed.
 func (i *Iterator) Close() error {
-	if i.tracker != nil {
+	if i.trackerHandle.IsValid() {
 		i.tracker.Stop(i.trackerHandle)
+		i.trackerHandle = 0
 	}
 	// Close the child iterator before releasing the readState because when the
 	// readState is released sstables referenced by the readState may be deleted
@@ -2900,9 +2903,9 @@ func (i *Iterator) CloneWithContext(ctx context.Context, opts CloneOptions) (*It
 		newIters:            i.newIters,
 		newIterRangeKey:     i.newIterRangeKey,
 		seqNum:              i.seqNum,
+		tracker:             i.tracker,
 	}
-	if i.tracker != nil {
-		dbi.tracker = i.tracker
+	if i.tracker != nil && !dbi.opts.ExemptFromTracking {
 		dbi.trackerHandle = i.tracker.Start()
 	}
 	if i.batch != nil {

metamorphic/ops.go

@@ -1181,9 +1181,6 @@ const debugIterators = false
 func (o *newIterOp) run(t *Test, h historyRecorder) {
 	r := t.getReader(o.readerID)
 	opts := iterOptions(t.testOpts.KeyFormat, o.iterOpts)
-	if debugIterators {
-		opts.DebugRangeKeyStack = true
-	}
 
 	var i *pebble.Iterator
 	for {
@@ -1261,9 +1258,14 @@ type newIterUsingCloneOp struct {
 func (o *newIterUsingCloneOp) run(t *Test, h historyRecorder) {
 	iter := t.getIter(o.existingIterID)
 	cloneOpts := pebble.CloneOptions{
-		IterOptions:      iterOptions(t.testOpts.KeyFormat, o.iterOpts),
 		RefreshBatchView: o.refreshBatch,
 	}
+	// We treat the zero options as an indication that we want to keep the options
+	// of the original iterator. This way, we don't depend on iterOptions() and
+	// whether it returns nil or not.
+	if !o.iterOpts.IsZero() {
+		cloneOpts.IterOptions = iterOptions(t.testOpts.KeyFormat, o.iterOpts)
+	}
 	i, err := iter.iter.Clone(cloneOpts)
 	if err != nil {
 		panic(err)
@@ -1377,7 +1379,10 @@ func (o *iterSetOptionsOp) formattedString(kf KeyFormat) string {
 }
 
 func iterOptions(kf KeyFormat, o iterOpts) *pebble.IterOptions {
-	if o.IsZero() && !debugIterators {
+	// Sometimes exempt from tracking.
+	exemptFromTracking := rand.IntN(4) == 0
+	if o.IsZero() && !debugIterators && !exemptFromTracking && rand.IntN(2) == 0 {
+		// Sometimes return nil if we are using the default options.
 		return nil
 	}
 	var lower, upper []byte
@@ -1395,6 +1400,7 @@ func iterOptions(kf KeyFormat, o iterOpts) *pebble.IterOptions {
 			Suffix: o.maskSuffix,
 		},
 		UseL6Filters:       o.useL6Filters,
+		ExemptFromTracking: exemptFromTracking,
 		DebugRangeKeyStack: debugIterators,
 	}
 	if opts.RangeKeyMasking.Suffix != nil {

options.go

@@ -207,6 +207,13 @@ type IterOptions struct {
 	// changed by calling SetOptions.
 	Category block.Category
 
+	// ExemptFromTracking indicates that we should not track the lifetime of the
+	// iterator (used to log information about long-lived iterators). Useful for
+	// hot paths where we know the iterator will be short-lived.
+	ExemptFromTracking bool
+
+	// DebugRangeKeyStack enables additional logging of the range key stack
+	// iterator, via keyspan.InjectLogging. Only used for debugging.
 	DebugRangeKeyStack bool
 
 	// Internal options.