Fix LRU deadlock + regression test and improve comments / logging

src/cmd/services/m3dbnode/config/cache.go

@@ -47,5 +47,6 @@ type SeriesCacheConfiguration struct {
 // LRUSeriesCachePolicyConfiguration contains configuration for the LRU
 // series caching policy.
 type LRUSeriesCachePolicyConfiguration struct {
-	MaxBlocks uint `yaml:"maxBlocks" validate:"nonzero"`
+	MaxBlocks         uint `yaml:"maxBlocks" validate:"nonzero"`
+	EventsChannelSize uint `yaml:"eventsChannelSize" validate:"nonzero"`
 }

src/dbnode/integration/setup.go

@@ -298,11 +298,13 @@ func newTestSetup(t *testing.T, opts testOptions, fsOpts fs.Options) (*testSetup
 
 	// Set up wired list if required
 	if storageOpts.SeriesCachePolicy() == series.CacheLRU {
-		wiredList := block.NewWiredList(
-			runtimeOptsMgr,
-			storageOpts.InstrumentOptions(),
-			storageOpts.ClockOptions(),
-		)
+		wiredList := block.NewWiredList(block.WiredListOptions{
+			RuntimeOptionsManager: runtimeOptsMgr,
+			InstrumentOptions:     storageOpts.InstrumentOptions(),
+			ClockOptions:          storageOpts.ClockOptions(),
+			// Use a small event channel size to stress-test the implementation
+			EventsChannelSize: 1,
+		})
 		blockOpts := storageOpts.DatabaseBlockOptions().SetWiredList(wiredList)
 		blockPool := block.NewDatabaseBlockPool(nil)
 		// Have to manually set the blockpool because the default one uses a constructor

src/dbnode/server/server.go

@@ -326,7 +326,7 @@ func Run(runOpts RunOptions) {
 	opts = opts.SetSeriesCachePolicy(seriesCachePolicy)
 
 	// Apply pooling options
-	opts = withEncodingAndPoolingOptions(logger, opts, cfg.PoolingPolicy)
+	opts = withEncodingAndPoolingOptions(cfg, logger, opts, cfg.PoolingPolicy)
 
 	// Setup the block retriever
 	switch seriesCachePolicy {
@@ -882,6 +882,7 @@ func kvWatchBootstrappers(
 }
 
 func withEncodingAndPoolingOptions(
+	cfg config.DBConfiguration,
 	logger xlog.Logger,
 	opts storage.Options,
 	policy config.PoolingPolicy,
@@ -1003,8 +1004,20 @@ func withEncodingAndPoolingOptions(
 		SetBytesPool(bytesPool)
 
 	if opts.SeriesCachePolicy() == series.CacheLRU {
-		runtimeOpts := opts.RuntimeOptionsManager()
-		wiredList := block.NewWiredList(runtimeOpts, iopts, opts.ClockOptions())
+		var (
+			runtimeOpts   = opts.RuntimeOptionsManager()
+			wiredListOpts = block.WiredListOptions{
+				RuntimeOptionsManager: runtimeOpts,
+				InstrumentOptions:     iopts,
+				ClockOptions:          opts.ClockOptions(),
+			}
+			lruCfg = cfg.Cache.SeriesConfiguration().LRU
+		)
+
+		if lruCfg != nil && lruCfg.EventsChannelSize > 0 {
+			wiredListOpts.EventsChannelSize = int(lruCfg.EventsChannelSize)
+		}
+		wiredList := block.NewWiredList(wiredListOpts)
 		blockOpts = blockOpts.SetWiredList(wiredList)
 	}
 	blockPool := block.NewDatabaseBlockPool(poolOptions(policy.BlockPool,

src/dbnode/storage/block/block.go

@@ -73,9 +73,9 @@ type dbBlock struct {
 }
 
 type listState struct {
-	next                      DatabaseBlock
-	prev                      DatabaseBlock
-	nextPrevUpdatedAtUnixNano int64
+	next                  DatabaseBlock
+	prev                  DatabaseBlock
+	enteredListAtUnixNano int64
 }
 
 // NewDatabaseBlock creates a new DatabaseBlock instance.
@@ -414,19 +414,37 @@ func (b *dbBlock) resetRetrievableWithLock(
 }
 
 func (b *dbBlock) Discard() ts.Segment {
-	return b.closeAndDiscard()
+	seg, _ := b.closeAndDiscardConditionally(nil)
+	return seg
 }
 
 func (b *dbBlock) Close() {
-	segment := b.closeAndDiscard()
+	segment, _ := b.closeAndDiscardConditionally(nil)
 	segment.Finalize()
 }
 
-func (b *dbBlock) closeAndDiscard() ts.Segment {
+func (b *dbBlock) CloseIfFromDisk() bool {
+	segment, ok := b.closeAndDiscardConditionally(func(b *dbBlock) bool {
+		return b.wasRetrievedFromDisk
+	})
+	if !ok {
+		return false
+	}
+	segment.Finalize()
+	return true
+}
+
+func (b *dbBlock) closeAndDiscardConditionally(condition func(b *dbBlock) bool) (ts.Segment, bool) {
 	b.Lock()
+
+	if condition != nil && !condition(b) {
+		b.Unlock()
+		return ts.Segment{}, false
+	}
+
 	if b.closed {
 		b.Unlock()
-		return ts.Segment{}
+		return ts.Segment{}, true
 	}
 
 	segment := b.segment
@@ -439,7 +457,7 @@ func (b *dbBlock) closeAndDiscard() ts.Segment {
 		pool.Put(b)
 	}
 
-	return segment
+	return segment, true
 }
 
 func (b *dbBlock) resetMergeTargetWithLock() {
@@ -470,13 +488,13 @@ func (b *dbBlock) setPrev(value DatabaseBlock) {
 }
 
 // Should only be used by the WiredList.
-func (b *dbBlock) nextPrevUpdatedAtUnixNano() int64 {
-	return b.listState.nextPrevUpdatedAtUnixNano
+func (b *dbBlock) enteredListAtUnixNano() int64 {
+	return b.listState.enteredListAtUnixNano
 }
 
 // Should only be used by the WiredList.
-func (b *dbBlock) setNextPrevUpdatedAtUnixNano(value int64) {
-	b.listState.nextPrevUpdatedAtUnixNano = value
+func (b *dbBlock) setEnteredListAtUnixNano(value int64) {
+	b.listState.enteredListAtUnixNano = value
 }
 
 // wiredListEntry is a snapshot of a subset of the block's state that the WiredList

src/dbnode/storage/block/block_test.go

@@ -551,6 +551,18 @@ func TestDatabaseBlockStreamMergePerformsCopy(t *testing.T) {
 	require.NoError(t, iter.Err())
 }
 
+func TestDatabaseBlockCloseIfFromDisk(t *testing.T) {
+	var (
+		blockOpts        = NewOptions()
+		blockNotFromDisk = NewDatabaseBlock(time.Time{}, time.Hour, ts.Segment{}, blockOpts).(*dbBlock)
+		blockFromDisk    = NewDatabaseBlock(time.Time{}, time.Hour, ts.Segment{}, blockOpts).(*dbBlock)
+	)
+	blockFromDisk.wasRetrievedFromDisk = true
+
+	require.False(t, blockNotFromDisk.CloseIfFromDisk())
+	require.True(t, blockFromDisk.CloseIfFromDisk())
+}
+
 func TestDatabaseSeriesBlocksAddBlock(t *testing.T) {
 	now := time.Now()
 	blockTimes := []time.Time{now, now.Add(time.Second), now.Add(time.Minute), now.Add(-time.Second), now.Add(-time.Hour)}

src/dbnode/storage/block/types.go

@@ -197,6 +197,11 @@ type DatabaseBlock interface {
 	// Close closes the block.
 	Close()
 
+	// CloseIfFromDisk atomically checks if the disk was retrieved from disk, and
+	// if so, closes it. It is meant as a layered protection for the WiredList
+	// which should only close blocks that were retrieved from disk.
+	CloseIfFromDisk() bool
+
 	// SetOnEvictedFromWiredList sets the owner of the block
 	SetOnEvictedFromWiredList(OnEvictedFromWiredList)
 
@@ -213,8 +218,8 @@ type databaseBlock interface {
 	setNext(block DatabaseBlock)
 	prev() DatabaseBlock
 	setPrev(block DatabaseBlock)
-	nextPrevUpdatedAtUnixNano() int64
-	setNextPrevUpdatedAtUnixNano(value int64)
+	enteredListAtUnixNano() int64
+	setEnteredListAtUnixNano(value int64)
 	wiredListEntry() wiredListEntry
 }