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dmap.go
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dmap.go
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// Copyright 2018-2022 Burak Sezer
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package dmap
import (
"errors"
"fmt"
"time"
"github.com/buraksezer/olric/internal/cluster/partitions"
"github.com/buraksezer/olric/pkg/storage"
)
const nilTimeout = 0 * time.Second
var (
// ErrKeyNotFound is returned when a key could not be found.
ErrKeyNotFound = errors.New("key not found")
ErrDMapNotFound = errors.New("dmap not found")
ErrServerGone = errors.New("server is gone")
)
// DMap implements a single-hop distributed hash table.
type DMap struct {
name string
fragmentName string
s *Service
engine storage.Engine
config *dmapConfig
}
// Name exposes name of the DMap.
func (dm *DMap) Name() string {
return dm.name
}
// getDMap returns an initialized DMap instance, otherwise it returns ErrDMapNotFound.
func (s *Service) getDMap(name string) (*DMap, error) {
s.RLock()
defer s.RUnlock()
dm, ok := s.dmaps[name]
if !ok {
return nil, ErrDMapNotFound
}
return dm, nil
}
func (s *Service) fragmentName(name string) string {
return fmt.Sprintf("dmap.%s", name)
}
// NewDMap creates and returns a new DMap instance. It checks member count quorum
// and bootstrapping status before creating a new DMap.
func (s *Service) NewDMap(name string) (*DMap, error) {
// Check operation status first:
//
// * Checks member count in the cluster, returns ErrClusterQuorum if
// the quorum value cannot be satisfied,
// * Checks bootstrapping status and awaits for a short period before
// returning ErrRequest timeout.
if err := s.rt.CheckMemberCountQuorum(); err != nil {
return nil, err
}
// An Olric node has to be bootstrapped to function properly.
if err := s.rt.CheckBootstrap(); err != nil {
return nil, err
}
s.Lock()
defer s.Unlock()
dm, ok := s.dmaps[name]
if ok {
return dm, nil
}
dm = &DMap{
config: &dmapConfig{},
name: name,
fragmentName: s.fragmentName(name),
s: s,
}
if err := dm.config.load(s.config.DMaps, name); err != nil {
return nil, err
}
// It's a shortcut.
dm.engine = dm.config.engine.Implementation
s.dmaps[name] = dm
return dm, nil
}
// getOrCreate is a shortcut function to create a new DMap or get an already initialized DMap instance.
func (s *Service) getOrCreateDMap(name string) (*DMap, error) {
dm, err := s.getDMap(name)
if errors.Is(err, ErrDMapNotFound) {
return s.NewDMap(name)
}
return dm, err
}
func (dm *DMap) getPartitionByHKey(hkey uint64, kind partitions.Kind) *partitions.Partition {
var part *partitions.Partition
switch {
case kind == partitions.PRIMARY:
part = dm.s.primary.PartitionByHKey(hkey)
case kind == partitions.BACKUP:
part = dm.s.backup.PartitionByHKey(hkey)
default:
panic("unknown partition kind")
}
return part
}
func isKeyExpired(ttl int64) bool {
if ttl == 0 {
return false
}
// convert nanoseconds to milliseconds
res := (time.Now().UnixNano() / 1000000) >= ttl
if res {
// number of valid items removed from cache to free memory for new items.
EvictedTotal.Increase(1)
}
return res
}