etcd - 一個分布式一致性鍵值存儲系統

etcd是一個分布式一致性鍵值存儲系統，用于共享配置和服務發現，專注于：

• 簡單:良好定義的，面向用戶的API (gRPC)

• 安全： 帶有可選客戶端證書認證的自動TLS

• 快速:測試驗證，每秒10000寫入

• 可靠:使用Raft適當分布

etcd是Go編寫，并使用Raft一致性算法來管理高可用復制日志，架構如下圖所示：

下載安裝

$ mkdir -p $GOPATH/src/github.com/coreos $ cd !$ $ git clone https://github.com/coreos/etcd.git $ cd etcd $ ./build $ ./bin/etcd

另外一種下載安裝的方法：

直接下載etcd二進制 （包含etcd、etcdctl）
https://github.com/coreos/etcd/releases

測試

$ cd $GOPATH $ ./bin/etcd$ cd $GOPATH $ ETCDCTL_API=3 ./bin/etcdctl put foo bar# 輸出結果顯示OK，表示安裝成功 OK

搭建本地集群

$ go get github.com/mattn/goreman$ cd $GOPATH/src/github.com/coreos/etcd $ goreman -f Procfile start

查看本地集群的服務器列表

$ cd $GOPATH/src/github.com/coreos/etcd$ ./bin/etcdctl member list# 顯示結果8211f1d0f64f3269: name=infra1 peerURLs=http://127.0.0.1:12380 clientURLs=http://127.0.0.1:2379 isLeader=false 91bc3c398fb3c146: name=infra2 peerURLs=http://127.0.0.1:22380 clientURLs=http://127.0.0.1:22379 isLeader=true fd422379fda50e48: name=infra3 peerURLs=http://127.0.0.1:32380 clientURLs=http://127.0.0.1:32379 isLeader=false

存儲數據

export ETCDCTL_API=3$ ./bin/etcdctl put foo "Hello World!"OK$ ./bin/etcdctl get foofoo Hello World!$ ./bin/etcdctl --write-out="json" get foo{"header":{"cluster_id":17237436991929493444,"member_id":9372538179322589801,"revision":2,"raft_term":2},"kvs":[{"key":"Zm9v","create_revision":2,"mod_revision":2,"version":1,"value":"SGVsbG8gV29ybGQh"}],"count":1}

根據前綴查詢

$ ./bin/etcdctl put web1 value1 $ ./bin/etcdctl put web2 value2 $ ./bin/etcdctl put web3 value3$ ./bin/etcdctl get web --prefixweb1 value1 web2 value2 web3 value3

刪除數據

$ ./bin/etcdctl put key myvalue $ ./bin/etcdctl del key 1 $ ./bin/etcdctl get key // 查詢結果為空$ ./bin/etcdctl put k1 value1 $ ./bin/etcdctl put k2 value2 $ ./bin/etcdctl del k --prefix 2 $ ./bin/etcdctl get k --prefix // 查詢結果為空

事務寫入

$ ./bin/etcdctl put user1 bad OK $ ./bin/etcdctl txn --interactivecompares: // 輸入以下內容，輸入結束按 兩次回車 value("user1") = "bad" //如果 user1 = bad，則執行 get user1 success requests (get, put, del): get user1 //如果 user1 != bad，則執行 put user1 good failure requests (get, put, del): put user1 good // 運行結果，執行 success SUCCESSuser1 bad$ ./bin/etcdctl txn --interactive compares: value("user1") = "111" // 如果 user1 = 111，則執行 get user1 success requests (get, put, del): get user1 //如果 user1 != 111，則執行 put user1 2222 failure requests (get, put, del): put user1 2222 // 運行結果，執行 failure FAILUREOK$ ./bin/etcdctl get user1 user1 2222

watch

// 當 stock1 的數值改變（ put 方法）的時候，watch 會收到通知 $ ./bin/etcdctl watch stock1 // 新打開終端 $ export ETCDCTL_API=3 $ ./bin/etcdctl put stock1 1000 //在watch 終端顯示 PUT stock1 1000$ ./bin/etcdctl watch stock --prefix $ ./bin/etcdctl put stock1 10 $ ./bin/etcdctl put stock2 20

lease

$ ./bin/etcdctl lease grant 300 # lease 326963a02758b527 granted with TTL(300s)$ ./bin/etcdctl put sample value --lease=326963a02758b527 OK$ ./bin/etcdctl get sample$ ./bin/etcdctl lease keep-alive 326963a02758b520 $ ./bin/etcdctl lease revoke 326963a02758b527 lease 326963a02758b527 revoked# or after 300 seconds $ ./bin/etcdctl get sample

Distributed locks

//第一終端 $ ./bin/etcdctl lock mutex1 mutex1/326963a02758b52d# 第二終端 $ ./bin/etcdctl lock mutex1// 當第一個終端結束了，第二個終端會顯示 mutex1/326963a02758b531

Elections

$ ./bin/etcdctl elect one p1one/326963a02758b539 p1# another client with the same name blocks $ ./bin/etcdctl elect one p2 //結束第一終端，第二終端顯示 one/326963a02758b53e p2

Cluster status

集群狀態

$ ./bin/etcdctl --write-out=table endpoint status$ ./bin/etcdctl endpoint health

Snapshot

./bin/etcdctl snapshot save my.dbSnapshot saved at my.db./bin/etcdctl --write-out=table snapshot status my.db

Member

./bin/etcdctl member list -w table

總結

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