/
alloc.go
84 lines (68 loc) · 1.67 KB
/
alloc.go
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// Copyright 2016 DeepFabric, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package pdserver
import (
"sync"
"github.com/pkg/errors"
)
const (
batch = uint64(1000)
)
type idAllocator struct {
sync.Mutex
store Store
leaderSignatureFn func() string
base uint64
end uint64
}
func newIDAllocator(store Store, leaderSignatureFn func() string) *idAllocator {
return &idAllocator{
store: store,
leaderSignatureFn: leaderSignatureFn,
}
}
func (alloc *idAllocator) newID() (uint64, error) {
alloc.Lock()
defer alloc.Unlock()
if alloc.base == alloc.end {
end, err := alloc.generate()
if err != nil {
return 0, errors.Wrap(err, "")
}
alloc.end = end
alloc.base = alloc.end - batch
}
alloc.base++
return alloc.base, nil
}
func (alloc *idAllocator) generate() (uint64, error) {
value, err := alloc.store.GetID()
if err != nil {
return 0, errors.Wrap(err, "")
}
max := value + batch
// create id
if value == 0 {
max := value + batch
err := alloc.store.CreateID(alloc.leaderSignatureFn(), max)
if err != nil {
return 0, err
}
return max, nil
}
err = alloc.store.UpdateID(alloc.leaderSignatureFn(), value, max)
if err != nil {
return 0, err
}
return max, nil
}