英文:
What is the appropriate way to multithread LevelDB in Go?
问题
我在我的项目中实现了levigo包装器，以便可以使用LevelDB。声明部分相当标准，如下所示：
func NewLeveldbStorage(dbPath string) *leveldbStorage {
opts := levigo.NewOptions()
opts.SetCache(levigo.NewLRUCache(3<<30))
opts.SetCreateIfMissing(true)
log.Debugf("Entering Open")
db, err := levigo.Open(dbPath, opts)
if err != nil {
log.Fatal("BOOM %v", err)
}
log.Debugf("Finished calling open")
opts.Close()
return &leveldbStorage{db: db}
}
这是返回的结构体：
type leveldbStorage struct {
db *levigo.DB
}
然后，我在这个结构体上进行了一些简单的GET和STORE命令，实际上只是使用s.db.Get和s.db.Put。这在我的测试中运行良好，但是当我运行以下基准测试时：
func BenchmarkLeviDbGet(b *testing.B) {
s := storage.NewLeveldbStorage("/path/to/db")
value := "value"
uid, _ := s.Store(value)
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.Get(uid)
}
}
运行该基准测试时，返回以下错误信息：
2014/10/12 21:17:09 BOOM %vIO error: lock /path/to/db/LOCK: already held by process
有没有适当的方法可以使用levigo/leveldb实现多线程读取？写入呢？如果多线程写入不可行，我不会感到惊讶，但是多线程读取似乎是可行的。我在这里做错了什么？
英文:
I have implemented the levigo wrapper in my project so I can use LevelDB. The declaration is fairly boilerplate, like so:
func NewLeveldbStorage(dbPath string) *leveldbStorage {
opts := levigo.NewOptions()
opts.SetCache(levigo.NewLRUCache(3<<30))
opts.SetCreateIfMissing(true)
log.Debugf("Entering Open")
db, err := levigo.Open(dbPath, opts); if err != nil {
log.Fatal("BOOM %v", err)
}
log.Debugf("Finished calling open")
opts.Close()
return &leveldbStorage{db:db}
}
Here is the struct returned:
type leveldbStorage struct {
db *levigo.DB
}
I then made a few simple GET and STORE commands on the struct that essentially just use s.db.Get and s.db.Put. This works fine in my tests, but when I run the following benchmark:
func BenchmarkLeviDbGet(b *testing.B) {
s := storage.NewLeveldbStorage("/path/to/db")
value := "value"
uid,_ := s.Store(value)
b.ResetTimer()
for i := 0; i < b.N; i++ {
s.Get(uid)
}
This benchmark, when run, returns:
2014/10/12 21:17:09 BOOM %vIO error: lock /path/to/db/LOCK: already held by process
Is there an appropriate way to use levigo/leveldb to enable multithreaded reading? What about writing? I would not be surprised if multithreaded writing is not possible, but multithreaded reading seems like it should be. What am I doing wrong here?
答案1
得分: 2
你需要关闭数据库文件或者使用一个全局实例来操作它，不能多次打开同一个文件，但是你可以在多个 goroutine 中访问同一个实例。
英文:
You either need to close the database file or use a global instance to it, you can't open the file multiple times, you can however access the same instance from multiple goroutines.
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