forked from TrueCloudLab/frostfs-node
a1696a81b6
There is a need to limit disk space used by write-cache. It is almost impossible to calculate the value exactly. It is proposed to estimate the size of the cache by the number of objects stored in it. Track amounts of objects saved in DB and FSTree separately. To do this, `ObjectCounters` interface is defined. It is generalized to a store of numbers that can be made persistent (new option `WithObjectCounters`). By default DB number is calculated as key number in default bucket, and FS number is set same to DB since it is currently hard to read the actual value from `FSTree` instance. Each PUT/DELETE operation to DB or FS increases/decreases corresponding counter. Before each PUT op an overflow check is performed with the following formula for evaluating the occupied space: `NumDB * MaxDBSize + NumFS * MaxFSSize`. If next PUT can cause write-cache overflow, object is written to the main storage. By default maximum write-cache size is set to 1GB. Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
103 lines
2 KiB
Go
103 lines
2 KiB
Go
package writecache
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import (
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"fmt"
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"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
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"go.etcd.io/bbolt"
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"go.uber.org/atomic"
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)
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// ObjectCounters is an interface of the storage of cached object amount.
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type ObjectCounters interface {
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// Increments number of objects saved in DB.
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IncDB()
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// Decrements number of objects saved in DB.
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DecDB()
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// Returns number of objects saved in DB.
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DB() uint64
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// Increments number of objects saved in FSTree.
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IncFS()
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// Decrements number of objects saved in FSTree.
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DecFS()
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// Returns number of objects saved in FSTree.
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FS() uint64
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// Reads number of objects saved in write-cache. It is called on write-cache initialization step.
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Read() error
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// Flushes the values and closes the storage. It is called on write-cache shutdown.
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FlushAndClose()
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}
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func (c *cache) estimateCacheSize() uint64 {
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return c.objCounters.DB()*c.smallObjectSize + c.objCounters.FS()*c.maxObjectSize
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}
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func (c *cache) incSizeDB(sz uint64) uint64 {
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return sz + c.smallObjectSize
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}
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func (c *cache) incSizeFS(sz uint64) uint64 {
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return sz + c.maxObjectSize
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}
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type counters struct {
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cDB, cFS atomic.Uint64
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db *bbolt.DB
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fs *fstree.FSTree
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}
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func (x *counters) IncDB() {
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x.cDB.Inc()
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}
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func (x *counters) DecDB() {
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x.cDB.Dec()
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}
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func (x *counters) DB() uint64 {
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return x.cDB.Load()
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}
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func (x *counters) IncFS() {
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x.cFS.Inc()
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}
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func (x *counters) DecFS() {
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x.cFS.Dec()
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}
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func (x *counters) FS() uint64 {
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return x.cFS.Load()
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}
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func (x *counters) Read() error {
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var inDB uint64
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err := x.db.View(func(tx *bbolt.Tx) error {
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b := tx.Bucket(defaultBucket)
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if b != nil {
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inDB = uint64(b.Stats().KeyN)
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}
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return nil
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})
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if err != nil {
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return fmt.Errorf("could not read write-cache DB counter: %w", err)
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}
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x.cDB.Store(inDB)
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// FIXME: calculate the actual value in FSTree (new method?).
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// For now we can think that db/fs = 50/50.
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x.cFS.Store(inDB)
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return nil
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}
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func (x *counters) FlushAndClose() {
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// values aren't stored
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}
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