[#472] blobstor: implement write-cache

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/local_object_storage/writecache/persist.go

@@ -0,0 +1,124 @@
+package writecache
+
+import (
+	"sort"
+	"time"
+
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+)
+
+const defaultPersistInterval = time.Second
+
+// persistLoop persists object accumulated in memory to the database.
+func (c *cache) persistLoop() {
+	tick := time.NewTicker(defaultPersistInterval)
+	defer tick.Stop()
+
+	for {
+		select {
+		case <-tick.C:
+			c.mtx.RLock()
+			m := c.mem
+			c.mtx.RUnlock()
+
+			sort.Slice(m, func(i, j int) bool { return m[i].addr < m[j].addr })
+
+			start := time.Now()
+			c.persistObjects(m)
+			c.log.Debug("persisted items to disk",
+				zap.Duration("took", time.Since(start)),
+				zap.Int("total", len(m)))
+
+			c.mtx.Lock()
+			n := copy(c.mem, c.mem[len(m):])
+			c.mem = c.mem[:n]
+			for i := range c.mem {
+				c.curMemSize += uint64(len(c.mem[i].data))
+			}
+			c.mtx.Unlock()
+
+			sz := 0
+			for i := range m {
+				sz += len(m[i].addr) + m[i].obj.ToV2().StableSize()
+			}
+			c.dbSize.Add(uint64(sz))
+
+		case <-c.closeCh:
+			return
+		}
+	}
+}
+
+func (c *cache) persistToCache(objs []objectInfo) []int {
+	var (
+		failMem []int
+		doneMem []int
+	)
+
+	_ = c.db.Update(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		for i := range objs {
+			if uint64(len(objs[i].data)) >= c.smallObjectSize {
+				failMem = append(failMem, i)
+				continue
+			}
+
+			err := b.Put([]byte(objs[i].addr), objs[i].data)
+			if err != nil {
+				return err
+			}
+
+			doneMem = append(doneMem, i)
+		}
+		return nil
+	})
+
+	if len(doneMem) > 0 {
+		c.evictObjects(len(doneMem))
+		for _, i := range doneMem {
+			c.flushed.Add(objs[i].addr, true)
+		}
+	}
+
+	var failDisk []int
+
+	for _, i := range failMem {
+		if uint64(len(objs[i].data)) > c.maxObjectSize {
+			failDisk = append(failDisk, i)
+			continue
+		}
+
+		err := c.fsTree.Put(objs[i].obj.Address(), objs[i].data)
+		if err != nil {
+			failDisk = append(failDisk, i)
+		}
+	}
+
+	return failDisk
+}
+
+// persistObjects tries to write objects from memory to the persistent storage.
+// If tryCache is false, writing skips cache and is done directly to the main storage.
+func (c *cache) persistObjects(objs []objectInfo) {
+	toDisk := c.persistToCache(objs)
+	j := 0
+
+	for i := range objs {
+		ch := c.metaCh
+		if j < len(toDisk) {
+			if i == toDisk[j] {
+				ch = c.directCh
+			} else {
+				for ; j < len(toDisk) && i > toDisk[j]; j++ {
+				}
+			}
+		}
+
+		select {
+		case ch <- objs[j].obj:
+		case <-c.closeCh:
+			return
+		}
+	}
+}