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queuestore.go
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queuestore.go
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// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package target
import (
"encoding/json"
"io/ioutil"
"math"
"os"
"path/filepath"
"sort"
"sync"
"github.com/memoio/minio/internal/event"
)
const (
defaultLimit = 100000 // Default store limit.
eventExt = ".event"
)
// QueueStore - Filestore for persisting events.
type QueueStore struct {
sync.RWMutex
currentEntries uint64
entryLimit uint64
directory string
}
// NewQueueStore - Creates an instance for QueueStore.
func NewQueueStore(directory string, limit uint64) Store {
if limit == 0 {
limit = defaultLimit
}
return &QueueStore{
directory: directory,
entryLimit: limit,
}
}
// Open - Creates the directory if not present.
func (store *QueueStore) Open() error {
store.Lock()
defer store.Unlock()
if err := os.MkdirAll(store.directory, os.FileMode(0o770)); err != nil {
return err
}
names, err := store.list()
if err != nil {
return err
}
currentEntries := uint64(len(names))
if currentEntries >= store.entryLimit {
return errLimitExceeded
}
store.currentEntries = currentEntries
return nil
}
// write - writes event to the directory.
func (store *QueueStore) write(key string, e event.Event) error {
// Marshalls the event.
eventData, err := json.Marshal(e)
if err != nil {
return err
}
path := filepath.Join(store.directory, key+eventExt)
if err := ioutil.WriteFile(path, eventData, os.FileMode(0o770)); err != nil {
return err
}
// Increment the event count.
store.currentEntries++
return nil
}
// Put - puts a event to the store.
func (store *QueueStore) Put(e event.Event) error {
store.Lock()
defer store.Unlock()
if store.currentEntries >= store.entryLimit {
return errLimitExceeded
}
key, err := getNewUUID()
if err != nil {
return err
}
return store.write(key, e)
}
// Get - gets a event from the store.
func (store *QueueStore) Get(key string) (event event.Event, err error) {
store.RLock()
defer func(store *QueueStore) {
store.RUnlock()
if err != nil {
// Upon error we remove the entry.
store.Del(key)
}
}(store)
var eventData []byte
eventData, err = ioutil.ReadFile(filepath.Join(store.directory, key+eventExt))
if err != nil {
return event, err
}
if len(eventData) == 0 {
return event, os.ErrNotExist
}
if err = json.Unmarshal(eventData, &event); err != nil {
return event, err
}
return event, nil
}
// Del - Deletes an entry from the store.
func (store *QueueStore) Del(key string) error {
store.Lock()
defer store.Unlock()
return store.del(key)
}
// lockless call
func (store *QueueStore) del(key string) error {
if err := os.Remove(filepath.Join(store.directory, key+eventExt)); err != nil {
return err
}
// Decrement the current entries count.
store.currentEntries--
// Current entries can underflow, when multiple
// events are being pushed in parallel, this code
// is needed to ensure that we don't underflow.
//
// queueStore replayEvents is not serialized,
// this code is needed to protect us under
// such situations.
if store.currentEntries == math.MaxUint64 {
store.currentEntries = 0
}
return nil
}
// List - lists all files from the directory.
func (store *QueueStore) List() ([]string, error) {
store.RLock()
defer store.RUnlock()
return store.list()
}
// list lock less.
func (store *QueueStore) list() ([]string, error) {
var names []string
files, err := ioutil.ReadDir(store.directory)
if err != nil {
return names, err
}
// Sort the dentries.
sort.Slice(files, func(i, j int) bool {
return files[i].ModTime().Before(files[j].ModTime())
})
for _, file := range files {
names = append(names, file.Name())
}
return names, nil
}