Address review part 2

blockstore/autobatch.go

@@ -25,12 +25,13 @@ type AutobatchBlockstore struct {
 	// TODO: drop if memory consumption is too high
 	addedCids map[cid.Cid]struct{}
 
-	lock          sync.Mutex
+	stateLock     sync.Mutex
+	doFlushLock   sync.Mutex
 	bufferedBatch blockBatch
 
-	// the flush worker has sole control (including read) over the flushingBatch.blockList and flushErr until shutdown
+	flushingBatch   blockBatch
-	flushingBatch blockBatch
+	flushErr        error
-	flushErr      error
+	flushWorkerDone bool
 
 	flushCh chan struct{}
 
@@ -51,12 +52,13 @@ func NewAutobatch(ctx context.Context, backingBs Blockstore, bufferCapacity int)
 		bufferCapacity: bufferCapacity,
 		flushCtx:       ctx,
 		flushCh:        make(chan struct{}, 1),
+		shutdownCh:     make(chan struct{}),
 		// could be made configable
 		flushRetryDelay: time.Millisecond * 100,
+		flushWorkerDone: false,
 	}
 
 	bs.bufferedBatch.blockMap = make(map[cid.Cid]block.Block)
-	bs.flushingBatch.blockMap = make(map[cid.Cid]block.Block)
 
 	go bs.flushWorker()
 
@@ -64,8 +66,8 @@ func NewAutobatch(ctx context.Context, backingBs Blockstore, bufferCapacity int)
 }
 
 func (bs *AutobatchBlockstore) Put(ctx context.Context, blk block.Block) error {
-	bs.lock.Lock()
+	bs.stateLock.Lock()
-	defer bs.lock.Unlock()
+	defer bs.stateLock.Unlock()
 
 	_, ok := bs.addedCids[blk.Cid()]
 	if !ok {
@@ -87,6 +89,11 @@ func (bs *AutobatchBlockstore) Put(ctx context.Context, blk block.Block) error {
 }
 
 func (bs *AutobatchBlockstore) flushWorker() {
+	defer func() {
+		bs.stateLock.Lock()
+		bs.flushWorkerDone = true
+		bs.stateLock.Unlock()
+	}()
 	for {
 		select {
 		case <-bs.flushCh:
@@ -106,34 +113,47 @@ func (bs *AutobatchBlockstore) flushWorker() {
 	}
 }
 
-// caller must NOT hold lock
+// caller must NOT hold stateLock
 func (bs *AutobatchBlockstore) doFlush(ctx context.Context) error {
+	bs.doFlushLock.Lock()
+	defer bs.doFlushLock.Unlock()
 	if bs.flushErr == nil {
-		bs.lock.Lock()
+		bs.stateLock.Lock()
 		// We do NOT clear addedCids here, because its purpose is to expedite Puts
 		bs.flushingBatch = bs.bufferedBatch
 		bs.bufferedBatch.blockList = make([]block.Block, 0, len(bs.flushingBatch.blockList))
 		bs.bufferedBatch.blockMap = make(map[cid.Cid]block.Block, len(bs.flushingBatch.blockMap))
-		bs.lock.Unlock()
+		bs.stateLock.Unlock()
 	}
 
 	bs.flushErr = bs.backingBs.PutMany(ctx, bs.flushingBatch.blockList)
+	bs.stateLock.Lock()
+	bs.flushingBatch = blockBatch{}
+	bs.stateLock.Unlock()
+
 	return bs.flushErr
 }
 
-// caller must NOT hold lock
+// caller must NOT hold stateLock
 func (bs *AutobatchBlockstore) Flush(ctx context.Context) error {
 	return bs.doFlush(ctx)
 }
 
 func (bs *AutobatchBlockstore) Shutdown(ctx context.Context) error {
-	// shutdown the flush worker
+	bs.stateLock.Lock()
-	bs.shutdownCh <- struct{}{}
+	flushDone := bs.flushWorkerDone
+	bs.stateLock.Unlock()
+	if !flushDone {
+		// may racily block forever if Shutdown is called in parallel
+		bs.shutdownCh <- struct{}{}
+	}
 
 	return bs.flushErr
 }
 
 func (bs *AutobatchBlockstore) Get(ctx context.Context, c cid.Cid) (block.Block, error) {
+	bs.stateLock.Lock()
+	defer bs.stateLock.Unlock()
 	// may seem backward to check the backingBs first, but that is the likeliest case
 	blk, err := bs.backingBs.Get(ctx, c)
 	if err == nil {
@@ -144,20 +164,17 @@ func (bs *AutobatchBlockstore) Get(ctx context.Context, c cid.Cid) (block.Block,
 		return blk, err
 	}
 
-	bs.lock.Lock()
-	defer bs.lock.Unlock()
 	v, ok := bs.flushingBatch.blockMap[c]
 	if ok {
 		return v, nil
 	}
 
-	v, ok = bs.flushingBatch.blockMap[c]
+	v, ok = bs.bufferedBatch.blockMap[c]
 	if ok {
 		return v, nil
 	}
 
-	// check the backingBs in case it just got put in the backingBs (and removed from the batch maps) while we were here
+	return nil, ErrNotFound
-	return bs.backingBs.Get(ctx, c)
 }
 
 func (bs *AutobatchBlockstore) DeleteBlock(context.Context, cid.Cid) error {
@@ -218,9 +235,10 @@ func (bs *AutobatchBlockstore) HashOnRead(enabled bool) {
 }
 
 func (bs *AutobatchBlockstore) View(ctx context.Context, cid cid.Cid, callback func([]byte) error) error {
-	if err := bs.Flush(ctx); err != nil {
+	blk, err := bs.Get(ctx, cid)
+	if err != nil {
 		return err
 	}
 
-	return bs.backingBs.View(ctx, cid, callback)
+	return callback(blk.RawData())
 }

blockstore/autobatch_test.go

@@ -17,8 +17,6 @@ func TestAutobatchBlockstore(t *testing.T) {
 	require.NoError(t, ab.Put(ctx, b1))
 	require.NoError(t, ab.Put(ctx, b2))
 
-	ab.Flush(ctx)
-
 	v0, err := ab.Get(ctx, b0.Cid())
 	require.NoError(t, err)
 	require.Equal(t, b0.RawData(), v0.RawData())
@@ -30,4 +28,7 @@ func TestAutobatchBlockstore(t *testing.T) {
 	v2, err := ab.Get(ctx, b2.Cid())
 	require.NoError(t, err)
 	require.Equal(t, b2.RawData(), v2.RawData())
+
+	require.NoError(t, ab.Flush(ctx))
+	require.NoError(t, ab.Shutdown(ctx))
 }