Kubernetes (通常称为 K8s) 是来自 Google 云平台的开源容器集群管理系统

bbolt ===== [](https://goreportcard.com/report/github.com/etcd-io/bbolt) [](https://codecov.io/gh/etcd-io/bbolt) [](https://travis-ci.com/etcd-io/bbolt) [](https://godoc.org/github.com/etcd-io/bbolt) [](https://github.com/etcd-io/bbolt/releases) [](https://github.com/etcd-io/bbolt/blob/master/LICENSE) bbolt is a fork of [Ben Johnson's][gh_ben] [Bolt][bolt] key/value store. The purpose of this fork is to provide the Go community with an active maintenance and development target for Bolt; the goal is improved reliability and stability. bbolt includes bug fixes, performance enhancements, and features not found in Bolt while preserving backwards compatibility with the Bolt API. Bolt is a pure Go key/value store inspired by [Howard Chu's][hyc_symas] [LMDB project][lmdb]. The goal of the project is to provide a simple, fast, and reliable database for projects that don't require a full database server such as Postgres or MySQL. Since Bolt is meant to be used as such a low-level piece of functionality, simplicity is key. The API will be small and only focus on getting values and setting values. That's it. [gh_ben]: https://github.com/benbjohnson [bolt]: https://github.com/boltdb/bolt [hyc_symas]: https://twitter.com/hyc_symas [lmdb]: https://www.symas.com/symas-embedded-database-lmdb ## Project Status Bolt is stable, the API is fixed, and the file format is fixed. Full unit test coverage and randomized black box testing are used to ensure database consistency and thread safety. Bolt is currently used in high-load production environments serving databases as large as 1TB. Many companies such as Shopify and Heroku use Bolt-backed services every day. ## Project versioning bbolt uses [semantic versioning](http://semver.org). API should not change between patch and minor releases. New minor versions may add additional features to the API. ## Table of Contents - [Getting Started](#getting-started) - [Installing](#installing) - [Opening a database](#opening-a-database) - [Transactions](#transactions) - [Read-write transactions](#read-write-transactions) - [Read-only transactions](#read-only-transactions) - [Batch read-write transactions](#batch-read-write-transactions) - [Managing transactions manually](#managing-transactions-manually) - [Using buckets](#using-buckets) - [Using key/value pairs](#using-keyvalue-pairs) - [Autoincrementing integer for the bucket](#autoincrementing-integer-for-the-bucket) - [Iterating over keys](#iterating-over-keys) - [Prefix scans](#prefix-scans) - [Range scans](#range-scans) - [ForEach()](#foreach) - [Nested buckets](#nested-buckets) - [Database backups](#database-backups) - [Statistics](#statistics) - [Read-Only Mode](#read-only-mode) - [Mobile Use (iOS/Android)](#mobile-use-iosandroid) - [Resources](#resources) - [Comparison with other databases](#comparison-with-other-databases) - [Postgres, MySQL, & other relational databases](#postgres-mysql--other-relational-databases) - [LevelDB, RocksDB](#leveldb-rocksdb) - [LMDB](#lmdb) - [Caveats & Limitations](#caveats--limitations) - [Reading the Source](#reading-the-source) - [Other Projects Using Bolt](#other-projects-using-bolt) ## Getting Started ### Installing To start using Bolt, install Go and run `go get`: ```sh $ go get go.etcd.io/bbolt@latest ``` This will retrieve the library and update your `go.mod` and `go.sum` files. To run the command line utility, execute: ```sh $ go run go.etcd.io/bbolt/cmd/bbolt@latest ``` Run `go install` to install the `bbolt` command line utility into your `$GOBIN` path, which defaults to `$GOPATH/bin` or `$HOME/go/bin` if the `GOPATH` environment variable is not set. ```sh $ go install go.etcd.io/bbolt/cmd/bbolt@latest ``` ### Importing bbolt To use bbolt as an embedded key-value store, import as: ```go import bolt "go.etcd.io/bbolt" db, err := bolt.Open(path, 0666, nil) if err != nil { return err } defer db.Close() ``` ### Opening a database The top-level object in Bolt is a `DB`. It is represented as a single file on your disk and represents a consistent snapshot of your data. To open your database, simply use the `bolt.Open()` function: ```go package main import ( "log" bolt "go.etcd.io/bbolt" ) func main() { // Open the my.db data file in your current directory. // It will be created if it doesn't exist. db, err := bolt.Open("my.db", 0600, nil) if err != nil { log.Fatal(err) } defer db.Close() ... } ``` Please note that 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: ```go db, err := bolt.Open("my.db", 0600, &bolt.Options{Timeout: 1 * time.Second}) ``` ### Transactions Bolt allows only one read-write transaction at a time but allows as many read-only transactions as you want at a time. Each transaction has a consistent view of the data as it existed when the transaction started. Individual transactions and all objects created from them (e.g. buckets, keys) are not thread safe. To work with data in multiple goroutines you must start a transaction for each one or use locking to ensure only one goroutine accesses a transaction at a time. Creating transaction from the `DB` is thread safe. Transactions should not depend on one another and generally shouldn't be opened simultaneously in the same goroutine. This can cause a deadlock as the read-write transaction needs to periodically re-map the data file but it cannot do so while any read-only transaction is open. Even a nested read-only transaction can cause a deadlock, as the child transaction can block the parent transaction from releasing its resources. #### Read-write transactions To start a read-write transaction, you can use the `DB.Update()` function: ```go err := db.Update(func(tx *bolt.Tx) error { ... return nil }) ``` Inside the closure, you have a consistent view of the database. You commit the transaction by returning `nil` at the end. You can also rollback the transaction at any point by returning an error. All database operations are allowed inside a read-write transaction. Always check the return error as it will report any disk failures that can cause your transaction to not complete. If you return an error within your closure it will be passed through. #### Read-only transactions To start a read-only transaction, you can use the `DB.View()` function: ```go err := db.View(func(tx *bolt.Tx) error { ... return nil }) ``` You also get a consistent view of the database within this closure, however, no mutating operations are allowed within a read-only transaction. You can only retrieve buckets, retrieve values, and copy the database within a read-only transaction. #### Batch read-write transactions Each `DB.Update()` waits for disk to commit the writes. This overhead can be minimized by combining multiple updates with the `DB.Batch()` function: ```go err := db.Batch(func(tx *bolt.Tx) error { ... return nil }) ``` Concurrent Batch calls are opportunistically combined into larger transactions. Batch is only useful when there are multiple goroutines calling it. The trade-off is that `Batch` can call the given function multiple times, if parts of