BoltDB

An embedded key/value database for Go (用Go实现的嵌入式键值存储) without a full database server such as Postgres or MySQL

etcd kv storage is boltdb

Feature

consistency and thread safety
support transaction

thread safety:

Bolt obtains a file lock on the data file so multiple processes cannot open the same database at the same time. Opening an already open Bolt database will cause it to hang until the other process closes it. To prevent an indefinite wait you can pass a timeout option to the Open() function:

db, err := bolt.Open("my.db", 0600, &bolt.Options{Timeout: 1 * time.Second})

Usage

Init

db, err := bolt.Open("my.db", 0600, &bolt.Options{Timeout: 1 * time.Second})
if err != nil {
   log.Fatal(err)
}
defer db.Close()

Update

Create Bucket

func createBucket(db *bolt.DB, name string) error {
   // write transaction
   return db.Update(func(tx *bolt.Tx) error {

      b := tx.Bucket([]byte(name))
      if b == nil {
         log.Printf("no bucket :%s\n",name)
         _, err := tx.CreateBucket([]byte(name))
         if err != nil {
            return err
         }
      } else {
         log.Printf("already exists bucket %s",name)
      }

      return nil
   })
}

Insert Key/Value into Bucket

func insertBucket(db *bolt.DB, name string, key, value []byte) error {
   return db.Update(func(tx *bolt.Tx) error {
      b := tx.Bucket([]byte(name))
      if b != nil {
         return b.Put(key, value)
      } else {
         return fmt.Errorf("No have this bucket :%s",name)
      }
   })
}

Read

func queryBucket(db *bolt.DB, name string, key []byte) ([]byte, error) {
   // read-only transaction
   var data []byte
   err := db.View(func(tx *bolt.Tx) error {
      b := tx.Bucket([]byte(name))
      if b != nil {
         data = b.Get(key)
         return nil
      } else {
         return fmt.Errorf("No have this bucket :%s",name)
      }
   })
   return data, err
}

Principle

Key words:

B+ Tree

Transaction

Lock-Free MVCC (Reader is not Locked)

mmap

if Wana know more about mmap u can click this article

Ref

https://byte_dance.fei_shu.cn/wiki/wikcnOJLqLIObcXsx9zMIkt8PMc#
www.cnblogs.com/X-knight/p/…
github.com/etcd-io/bbo…
https://tech.byte_dance.net/articles/6931533584406675463?from=lark_all_search
www.jianshu.com/p/b86a69892…

Boltdb - Must Know