frostfs-node/pkg/local_object_storage/writecache/mode.go

64 lines
1.8 KiB
Go

package writecache
import (
"errors"
"fmt"
"time"
"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard/mode"
)
// ErrReadOnly is returned when Put/Write is performed in a read-only mode.
var ErrReadOnly = errors.New("write-cache is in read-only mode")
// SetMode sets write-cache mode of operation.
// When shard is put in read-only mode all objects in memory are flushed to disk
// and all background jobs are suspended.
func (c *cache) SetMode(m mode.Mode) error {
c.modeMtx.Lock()
defer c.modeMtx.Unlock()
if m.ReadOnly() == c.readOnly() {
c.mode = m
return nil
}
if !c.readOnly() {
// Because modeMtx is taken no new objects will arrive an all other modifying
// operations are completed.
// 1. Persist objects already in memory on disk.
c.persistMemoryCache()
}
if c.db != nil {
if err := c.db.Close(); err != nil {
return fmt.Errorf("can't close write-cache database: %w", err)
}
c.db = nil
}
// 2. Suspend producers to ensure there are channel send operations in fly.
// metaCh and directCh can be populated either during Put or in background memory persist thread.
// Former possibility is eliminated by taking `modeMtx` mutex and
// latter by explicit persist in the previous step.
// flushCh is populated by `flush` with `modeMtx` is also taken.
// Thus all producers are shutdown and we only need to wait until all channels are empty.
for len(c.metaCh) != 0 || len(c.directCh) != 0 || len(c.flushCh) != 0 {
c.log.Info("waiting for channels to flush")
time.Sleep(time.Second)
}
if err := c.openStore(m.ReadOnly()); err != nil {
return err
}
c.mode = m
return nil
}
// readOnly returns true if current mode is read-only.
// `c.modeMtx` must be taken.
func (c *cache) readOnly() bool {
return c.mode.ReadOnly()
}