文章出處

閱讀目錄：

  • 主機安裝
  • 集群搭建
  • API 操作
  • API 說明和 etcdctl 命令說明

etcd 是 CoreOS 團隊發起的一個開源項目（Go 語言，其實很多這類項目都是 Go 語言實現的，只能說很強大），實現了分布式鍵值存儲和服務發現，etcd 和 ZooKeeper/Consul 非常相似，都提供了類似的功能，以及 REST API 的訪問操作，具有以下特點：

  • 簡單：安裝和使用簡單，提供了 REST API 進行操作交互
  • 安全：支持 HTTPS SSL 證書
  • 快速：支持并發 10 k/s 的讀寫操作
  • 可靠：采用 raft 算法，實現分布式系統數據的可用性和一致性

etcd 可以單個實例使用，也可以進行集群配置，因為很多項目都是以 etcd 作為服務發現，比如 CoreOS 和 Kubernetes，所以，下面我們使用 Docker 簡單搭建一下 etcd 集群。

1. 主機安裝

如果不使用 Docker 的話，etcd 在主機上安裝，也非常簡單。

Linux 安裝命令：

$ curl -L  https://github.com/coreos/etcd/releases/download/v3.3.0-rc.0/etcd-v3.3.0-rc.0-linux-amd64.tar.gz -o etcd-v3.3.0-rc.0-linux-amd64.tar.gz && 
sudo tar xzvf etcd-v3.3.0-rc.0-linux-amd64.tar.gz && 
cd etcd-v3.3.0-rc.0-linux-amd64 && 
sudo cp etcd* /usr/local/bin/

其實就是將編譯后的二進制文件，拷貝到/usr/local/bin/目錄，各個版本的二進制文件，可以從 https://github.com/coreos/etcd/releases/ 中查找下載。

Mac OS 安裝命令：

$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" < /dev/null 2> /dev/null
$ brew install etcd

執行下面命令，查看 etcd 是否安裝成功：

$ etcd --version
etcd Version: 3.2.12
Git SHA: GitNotFound
Go Version: go1.9.2
Go OS/Arch: darwin/amd64

2. 集群搭建

搭建 etcd 集群，需要借助下 Docker Machine 創建三個 Docker 主機，命令：

$ docker-machine create -d virtualbox manager1 && 
docker-machine create -d virtualbox worker1 && 
docker-machine create -d virtualbox worker2

$ docker-machine ls
NAME       ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
manager1   -        virtualbox   Running   tcp://192.168.99.100:2376           v17.11.0-ce   
worker1    -        virtualbox   Running   tcp://192.168.99.101:2376           v17.11.0-ce   
worker2    -        virtualbox   Running   tcp://192.168.99.102:2376           v17.11.0-ce

為防止 Docker 主機中垃取官方鏡像，速度慢的問題，我們還需要將 etcd 鏡像打包推送到私有倉庫中，命令：

$ docker tag quay.io/coreos/etcd 192.168.99.1:5000/quay.io/coreos/etcd:latest && 
docker push 192.168.99.1:5000/quay.io/coreos/etcd:latest && 
docker pull 192.168.99.1:5000/quay.io/coreos/etcd:latest

另外，還需要將私有倉庫地址配置在 Docker 主機中，并重啟三個 Docker 主機，具體配置參考：Docker 三劍客之 Docker Swarm

Docker 主機配置好之后，我們需要使用docker-machine ssh命令，分別進入三個 Docker 主機中，執行 Docker etcd 配置命令。

manager1 主機（node1 192.168.99.100）：

$ docker run -d --name etcd \
    -p 2379:2379 \
    -p 2380:2380 \
    --volume=etcd-data:/etcd-data \
    192.168.99.1:5000/quay.io/coreos/etcd \
    /usr/local/bin/etcd \
    --data-dir=/etcd-data --name node1 \
    --initial-advertise-peer-urls http://192.168.99.100:2380 --listen-peer-urls http://0.0.0.0:2380 \
    --advertise-client-urls http://192.168.99.100:2379 --listen-client-urls http://0.0.0.0:2379 \
    --initial-cluster-state new \
    --initial-cluster-token docker-etcd \
    --initial-cluster node1=http://192.168.99.100:2380,node2=http://192.168.99.101:2380,node3=http://192.168.99.102:2380

worker1 主機（node2 192.168.99.101）：

$ docker run -d --name etcd \
    -p 2379:2379 \
    -p 2380:2380 \
    --volume=etcd-data:/etcd-data \
    192.168.99.1:5000/quay.io/coreos/etcd \
    /usr/local/bin/etcd \
    --data-dir=/etcd-data --name node2 \
    --initial-advertise-peer-urls http://192.168.99.101:2380 --listen-peer-urls http://0.0.0.0:2380 \
    --advertise-client-urls http://192.168.99.101:2379 --listen-client-urls http://0.0.0.0:2379 \
    --initial-cluster-state new \
    --initial-cluster-token docker-etcd \
    --initial-cluster node1=http://192.168.99.100:2380,node2=http://192.168.99.101:2380,node3=http://192.168.99.102:2380

worker2 主機（node1 192.168.99.102）：

$ docker run -d --name etcd \
    -p 2379:2379 \
    -p 2380:2380 \
    --volume=etcd-data:/etcd-data \
    192.168.99.1:5000/quay.io/coreos/etcd \
    /usr/local/bin/etcd \
    --data-dir=/etcd-data --name node3 \
    --initial-advertise-peer-urls http://192.168.99.102:2380 --listen-peer-urls http://0.0.0.0:2380 \
    --advertise-client-urls http://192.168.99.102:2379 --listen-client-urls http://0.0.0.0:2379 \
    --initial-cluster-state existing \
    --initial-cluster-token docker-etcd \
    --initial-cluster node1=http://192.168.99.100:2380,node2=http://192.168.99.101:2380,node3=http://192.168.99.102:2380

先來說明下 etcd 各個配置參數的意思（參考自 etcd 使用入門）：

  • --name：節點名稱，默認為 default。
  • --data-dir：服務運行數據保存的路徑，默認為${name}.etcd。
  • --snapshot-count：指定有多少事務（transaction）被提交時，觸發截取快照保存到磁盤。
  • --heartbeat-interval：leader 多久發送一次心跳到 followers。默認值是 100ms。
  • --eletion-timeout：重新投票的超時時間，如果 follow 在該時間間隔沒有收到心跳包，會觸發重新投票，默認為 1000 ms。
  • --listen-peer-urls：和同伴通信的地址，比如http://ip:2380，如果有多個，使用逗號分隔。需要所有節點都能夠訪問，所以不要使用 localhost！
  • --listen-client-urls：對外提供服務的地址：比如http://ip:2379,http://127.0.0.1:2379，客戶端會連接到這里和 etcd 交互。
  • --advertise-client-urls：對外公告的該節點客戶端監聽地址，這個值會告訴集群中其他節點。
  • --initial-advertise-peer-urls：該節點同伴監聽地址，這個值會告訴集群中其他節點。
  • --initial-cluster：集群中所有節點的信息，格式為node1=http://ip1:2380,node2=http://ip2:2380,…，注意：這里的 node1 是節點的 --name 指定的名字；后面的 ip1:2380 是 --initial-advertise-peer-urls 指定的值。
  • --initial-cluster-state：新建集群的時候，這個值為 new；假如已經存在的集群，這個值為 existing。
  • --initial-cluster-token：創建集群的 token，這個值每個集群保持唯一。這樣的話，如果你要重新創建集群，即使配置和之前一樣，也會再次生成新的集群和節點 uuid；否則會導致多個集群之間的沖突，造成未知的錯誤。

上述配置也可以設置配置文件，默認為/etc/etcd/etcd.conf。

我們可以使用docker ps，查看 Docker etcd 是否配置成功：

$ docker ps
CONTAINER ID        IMAGE                                   COMMAND                  CREATED             STATUS              PORTS                              NAMES
463380d23dfe        192.168.99.1:5000/quay.io/coreos/etcd   "/usr/local/bin/et..."   2 hours ago         Up 2 hours          0.0.0.0:2379-2380->2379-2380/tcp   etcd

然后進入其中一個 Docker 主機：

$ docker exec -it etcd bin/sh

執行下面命令（查看集群成員）：

$ etcdctl member list
773d30c9fc6640b4: name=node2 peerURLs=http://192.168.99.101:2380 clientURLs=http://192.168.99.101:2379 isLeader=true
b2b0bca2e0cfcc19: name=node3 peerURLs=http://192.168.99.102:2380 clientURLs=http://192.168.99.102:2379 isLeader=false
c88e2cccbb287a01: name=node1 peerURLs=http://192.168.99.100:2380 clientURLs=http://192.168.99.100:2379 isLeader=false

可以看到，集群里面有三個成員，并且node2為管理員，node1和node3為普通成員。

etcdctl 是 ectd 的客戶端命令工具（也是 go 語言實現），里面封裝了 etcd 的 REST API 執行命令，方便我們進行操作 etcd，后面再列出 etcdctl 的命令詳細說明。

上面命令的 etcd API 版本為 2.0，我們可以手動設置版本為 3.0，命令：

$ export ETCDCTL_API=3 && /usr/local/bin/etcdctl put foo bar
OK

部分命令和執行結果還是和 2.0 版本，有很多不同的，比如同是查看集群成員，3.0 版本的執行結果：

$ etcdctl member list
773d30c9fc6640b4, started, node2, http://192.168.99.101:2380, http://192.168.99.101:2379
b2b0bca2e0cfcc19, started, node3, http://192.168.99.102:2380, http://192.168.99.102:2379
c88e2cccbb287a01, started, node1, http://192.168.99.100:2380, http://192.168.99.100:2379

好了，我們現在再演示一種情況，就是從集群中移除一個節點，然后再把它添加到集群中，為演示 etcd 中使用 Raft 算法，我們將node2管理節點，作為操作對象。

我們在隨便一個主機 etcd 容器中（node2除外），執行成員移除集群命令（必須使用 ID，使用別名會報錯）：

$ etcdctl member remove 773d30c9fc6640b4
Member 773d30c9fc6640b4 removed from cluster f84185fa5f91bdf6

我們再執行下查看集群成員命令（v2 版本）：

$ etcdctl member list
b2b0bca2e0cfcc19: name=node3 peerURLs=http://192.168.99.102:2380 clientURLs=http://192.168.99.102:2379 isLeader=true
c88e2cccbb287a01: name=node1 peerURLs=http://192.168.99.100:2380 clientURLs=http://192.168.99.100:2379 isLeader=false

會發現node2管理節點被移除集群了，并且通過 Raft 算法，node3被推舉為管理節點。

在將node2節點重新加入集群之前，我們需要執行下面命令：

$ etcdctl member add node2 --peer-urls="http://192.168.99.101:2380"
Member 22b0de6ffcd98f00 added to cluster f84185fa5f91bdf6

ETCD_NAME="node2"
ETCD_INITIAL_CLUSTER="node2=http://192.168.99.101:2380,node3=http://192.168.99.102:2380,node1=http://192.168.99.100:2380"
ETCD_INITIAL_CLUSTER_STATE="existing"

可以看到，ETCD_INITIAL_CLUSTER_STATE 值為existing，也就是我們配置的--initial-cluster-state參數。

我們再執行下查看集群成員命令（v2 版本）：

$ etcdctl member list
22b0de6ffcd98f00[unstarted]: peerURLs=http://192.168.99.101:2380
b2b0bca2e0cfcc19: name=node3 peerURLs=http://192.168.99.102:2380 clientURLs=http://192.168.99.102:2379 isLeader=true
c88e2cccbb287a01: name=node1 peerURLs=http://192.168.99.100:2380 clientURLs=http://192.168.99.100:2379 isLeader=false

會發現22b0de6ffcd98f00成員狀態變為了unstarted。

我們在node2節點，執行 Docker etcd 集群配置命令：

$ docker run -d --name etcd \
    -p 2379:2379 \
    -p 2380:2380 \
    --volume=etcd-data:/etcd-data \
    192.168.99.1:5000/quay.io/coreos/etcd \
    /usr/local/bin/etcd \
    --data-dir=/etcd-data --name node2 \
    --initial-advertise-peer-urls http://192.168.99.101:2380 --listen-peer-urls http://0.0.0.0:2380 \
    --advertise-client-urls http://192.168.99.101:2379 --listen-client-urls http://0.0.0.0:2379 \
    --initial-cluster-state existing \
    --initial-cluster-token docker-etcd \
    --initial-cluster node1=http://192.168.99.100:2380,node2=http://192.168.99.101:2380,node3=http://192.168.99.102:2380

結果并不像我們想要的那樣成功，執行查看日志：

$ docker logs etcd
2017-12-25 08:19:30.160967 I | etcdmain: etcd Version: 3.2.12
2017-12-25 08:19:30.161062 I | etcdmain: Git SHA: b19dae0
2017-12-25 08:19:30.161082 I | etcdmain: Go Version: go1.8.5
2017-12-25 08:19:30.161092 I | etcdmain: Go OS/Arch: linux/amd64
2017-12-25 08:19:30.161105 I | etcdmain: setting maximum number of CPUs to 1, total number of available CPUs is 1
2017-12-25 08:19:30.161144 N | etcdmain: the server is already initialized as member before, starting as etcd member...
2017-12-25 08:19:30.161195 I | embed: listening for peers on http://0.0.0.0:2380
2017-12-25 08:19:30.161232 I | embed: listening for client requests on 0.0.0.0:2379
2017-12-25 08:19:30.165269 I | etcdserver: name = node2
2017-12-25 08:19:30.165317 I | etcdserver: data dir = /etcd-data
2017-12-25 08:19:30.165335 I | etcdserver: member dir = /etcd-data/member
2017-12-25 08:19:30.165347 I | etcdserver: heartbeat = 100ms
2017-12-25 08:19:30.165358 I | etcdserver: election = 1000ms
2017-12-25 08:19:30.165369 I | etcdserver: snapshot count = 100000
2017-12-25 08:19:30.165385 I | etcdserver: advertise client URLs = http://192.168.99.101:2379
2017-12-25 08:19:30.165593 I | etcdserver: restarting member 773d30c9fc6640b4 in cluster f84185fa5f91bdf6 at commit index 14
2017-12-25 08:19:30.165627 I | raft: 773d30c9fc6640b4 became follower at term 11
2017-12-25 08:19:30.165647 I | raft: newRaft 773d30c9fc6640b4 [peers: [], term: 11, commit: 14, applied: 0, lastindex: 14, lastterm: 11]
2017-12-25 08:19:30.169277 W | auth: simple token is not cryptographically signed
2017-12-25 08:19:30.170424 I | etcdserver: starting server... [version: 3.2.12, cluster version: to_be_decided]
2017-12-25 08:19:30.171732 I | etcdserver/membership: added member 773d30c9fc6640b4 [http://192.168.99.101:2380] to cluster f84185fa5f91bdf6
2017-12-25 08:19:30.171845 I | etcdserver/membership: added member c88e2cccbb287a01 [http://192.168.99.100:2380] to cluster f84185fa5f91bdf6
2017-12-25 08:19:30.171877 I | rafthttp: starting peer c88e2cccbb287a01...
2017-12-25 08:19:30.171902 I | rafthttp: started HTTP pipelining with peer c88e2cccbb287a01
2017-12-25 08:19:30.175264 I | rafthttp: started peer c88e2cccbb287a01
2017-12-25 08:19:30.175339 I | rafthttp: added peer c88e2cccbb287a01
2017-12-25 08:19:30.178326 I | etcdserver/membership: added member cbd7fa8d01297113 [http://192.168.99.102:2380] to cluster f84185fa5f91bdf6
2017-12-25 08:19:30.178383 I | rafthttp: starting peer cbd7fa8d01297113...
2017-12-25 08:19:30.178410 I | rafthttp: started HTTP pipelining with peer cbd7fa8d01297113
2017-12-25 08:19:30.179794 I | rafthttp: started peer cbd7fa8d01297113
2017-12-25 08:19:30.179835 I | rafthttp: added peer cbd7fa8d01297113
2017-12-25 08:19:30.180062 N | etcdserver/membership: set the initial cluster version to 3.0
2017-12-25 08:19:30.180132 I | etcdserver/api: enabled capabilities for version 3.0
2017-12-25 08:19:30.180255 N | etcdserver/membership: updated the cluster version from 3.0 to 3.2
2017-12-25 08:19:30.180430 I | etcdserver/api: enabled capabilities for version 3.2
2017-12-25 08:19:30.183979 I | rafthttp: started streaming with peer c88e2cccbb287a01 (writer)
2017-12-25 08:19:30.184139 I | rafthttp: started streaming with peer c88e2cccbb287a01 (writer)
2017-12-25 08:19:30.184232 I | rafthttp: started streaming with peer c88e2cccbb287a01 (stream MsgApp v2 reader)
2017-12-25 08:19:30.185142 I | rafthttp: started streaming with peer c88e2cccbb287a01 (stream Message reader)
2017-12-25 08:19:30.186518 I | etcdserver/membership: removed member cbd7fa8d01297113 from cluster f84185fa5f91bdf6
2017-12-25 08:19:30.186573 I | rafthttp: stopping peer cbd7fa8d01297113...
2017-12-25 08:19:30.186614 I | rafthttp: started streaming with peer cbd7fa8d01297113 (writer)
2017-12-25 08:19:30.186786 I | rafthttp: stopped streaming with peer cbd7fa8d01297113 (writer)
2017-12-25 08:19:30.186815 I | rafthttp: started streaming with peer cbd7fa8d01297113 (writer)
2017-12-25 08:19:30.186831 I | rafthttp: stopped streaming with peer cbd7fa8d01297113 (writer)
2017-12-25 08:19:30.186876 I | rafthttp: started streaming with peer cbd7fa8d01297113 (stream MsgApp v2 reader)
2017-12-25 08:19:30.187224 I | rafthttp: started streaming with peer cbd7fa8d01297113 (stream Message reader)
2017-12-25 08:19:30.187647 I | rafthttp: stopped HTTP pipelining with peer cbd7fa8d01297113
2017-12-25 08:19:30.187682 I | rafthttp: stopped streaming with peer cbd7fa8d01297113 (stream MsgApp v2 reader)
2017-12-25 08:19:30.187873 I | rafthttp: stopped streaming with peer cbd7fa8d01297113 (stream Message reader)
2017-12-25 08:19:30.187895 I | rafthttp: stopped peer cbd7fa8d01297113
2017-12-25 08:19:30.187911 I | rafthttp: removed peer cbd7fa8d01297113
2017-12-25 08:19:30.188034 I | etcdserver/membership: added member b2b0bca2e0cfcc19 [http://192.168.99.102:2380] to cluster f84185fa5f91bdf6
2017-12-25 08:19:30.188059 I | rafthttp: starting peer b2b0bca2e0cfcc19...
2017-12-25 08:19:30.188075 I | rafthttp: started HTTP pipelining with peer b2b0bca2e0cfcc19
2017-12-25 08:19:30.188510 I | rafthttp: started peer b2b0bca2e0cfcc19
2017-12-25 08:19:30.188533 I | rafthttp: added peer b2b0bca2e0cfcc19
2017-12-25 08:19:30.188795 I | etcdserver/membership: removed member 773d30c9fc6640b4 from cluster f84185fa5f91bdf6
2017-12-25 08:19:30.193643 I | rafthttp: started streaming with peer b2b0bca2e0cfcc19 (writer)
2017-12-25 08:19:30.193730 I | rafthttp: started streaming with peer b2b0bca2e0cfcc19 (writer)
2017-12-25 08:19:30.193797 I | rafthttp: started streaming with peer b2b0bca2e0cfcc19 (stream MsgApp v2 reader)
2017-12-25 08:19:30.194782 I | rafthttp: started streaming with peer b2b0bca2e0cfcc19 (stream Message reader)
2017-12-25 08:19:30.195663 I | raft: 773d30c9fc6640b4 [term: 11] received a MsgHeartbeat message with higher term from b2b0bca2e0cfcc19 [term: 12]
2017-12-25 08:19:30.195716 I | raft: 773d30c9fc6640b4 became follower at term 12
2017-12-25 08:19:30.195736 I | raft: raft.node: 773d30c9fc6640b4 elected leader b2b0bca2e0cfcc19 at term 12
2017-12-25 08:19:30.196617 E | rafthttp: streaming request ignored (ID mismatch got 22b0de6ffcd98f00 want 773d30c9fc6640b4)
2017-12-25 08:19:30.197064 E | rafthttp: streaming request ignored (ID mismatch got 22b0de6ffcd98f00 want 773d30c9fc6640b4)
2017-12-25 08:19:30.197846 E | rafthttp: streaming request ignored (ID mismatch got 22b0de6ffcd98f00 want 773d30c9fc6640b4)
2017-12-25 08:19:30.198242 E | rafthttp: streaming request ignored (ID mismatch got 22b0de6ffcd98f00 want 773d30c9fc6640b4)
2017-12-25 08:19:30.201771 E | etcdserver: the member has been permanently removed from the cluster
2017-12-25 08:19:30.202060 I | etcdserver: the data-dir used by this member must be removed.
2017-12-25 08:19:30.202307 E | etcdserver: publish error: etcdserver: request cancelled
2017-12-25 08:19:30.202338 I | etcdserver: aborting publish because server is stopped
2017-12-25 08:19:30.202364 I | rafthttp: stopping peer b2b0bca2e0cfcc19...
2017-12-25 08:19:30.202482 I | rafthttp: stopped streaming with peer b2b0bca2e0cfcc19 (writer)
2017-12-25 08:19:30.202504 I | rafthttp: stopped streaming with peer b2b0bca2e0cfcc19 (writer)
2017-12-25 08:19:30.204143 I | rafthttp: stopped HTTP pipelining with peer b2b0bca2e0cfcc19
2017-12-25 08:19:30.204186 I | rafthttp: stopped streaming with peer b2b0bca2e0cfcc19 (stream MsgApp v2 reader)
2017-12-25 08:19:30.204205 I | rafthttp: stopped streaming with peer b2b0bca2e0cfcc19 (stream Message reader)
2017-12-25 08:19:30.204217 I | rafthttp: stopped peer b2b0bca2e0cfcc19
2017-12-25 08:19:30.204228 I | rafthttp: stopping peer c88e2cccbb287a01...
2017-12-25 08:19:30.204241 I | rafthttp: stopped streaming with peer c88e2cccbb287a01 (writer)
2017-12-25 08:19:30.204255 I | rafthttp: stopped streaming with peer c88e2cccbb287a01 (writer)
2017-12-25 08:19:30.204824 I | rafthttp: stopped HTTP pipelining with peer c88e2cccbb287a01
2017-12-25 08:19:30.204860 I | rafthttp: stopped streaming with peer c88e2cccbb287a01 (stream MsgApp v2 reader)
2017-12-25 08:19:30.204878 I | rafthttp: stopped streaming with peer c88e2cccbb287a01 (stream Message reader)
2017-12-25 08:19:30.204891 I | rafthttp: stopped peer c88e2cccbb287a01

這么長的日志，說明啥問題呢，就是說我們雖然重新執行的 etcd 創建命令，但因為讀取之前配置文件的關系，etcd 會恢復之前的集群成員，但之前的集群節點已經被移除了，所以集群節點就一直處于停止狀態。

怎么解決呢？很簡單，就是將我們之前創建的etcd-data數據卷軸刪掉，命令：

$ docker volume ls
DRIVER              VOLUME NAME
local               etcd-data

$ docker volume rm etcd-data
etcd-data

然后，再在node2節點，重新執行 Docker etcd 集群配置命令（上面），會發現執行是成功的。

我們再執行下查看集群成員命令（v2 版本）：

$ etcdctl member list
22b0de6ffcd98f00: name=node2 peerURLs=http://192.168.99.101:2380 clientURLs=http://192.168.99.101:2379 isLeader=false
b2b0bca2e0cfcc19: name=node3 peerURLs=http://192.168.99.102:2380 clientURLs=http://192.168.99.102:2379 isLeader=true
c88e2cccbb287a01: name=node1 peerURLs=http://192.168.99.100:2380 clientURLs=http://192.168.99.100:2379 isLeader=false

3. API 操作

etcd REST API 被用于鍵值操作和集群成員操作，這邊就簡單說幾個，詳細的 API 查看附錄說明。

1. 鍵值管理

設置鍵值命令：

$ curl http://127.0.0.1:2379/v2/keys/hello -XPUT -d value="hello world"
{"action":"set","node":{"key":"/hello","value":"hello world","modifiedIndex":17,"createdIndex":17}}

查看鍵值命令：

$ curl http://127.0.0.1:2379/v2/keys/hello
{"action":"get","node":{"key":"/hello","value":"hello world","modifiedIndex":17,"createdIndex":17}}

刪除鍵值命令：

$ curl http://127.0.0.1:2379/v2/keys/hello -XDELETE
{"action":"delete","node":{"key":"/hello","modifiedIndex":19,"createdIndex":17},"prevNode":{"key":"/hello","value":"hello world","modifiedIndex":17,"createdIndex":17}}

2. 成員管理

列出集群中的所有成員：

$ curl http://127.0.0.1:2379/v2/members
{"members":[{"id":"22b0de6ffcd98f00","name":"node2","peerURLs":["http://192.168.99.101:2380"],"clientURLs":["http://192.168.99.101:2379"]},{"id":"b2b0bca2e0cfcc19","name":"node3","peerURLs":["http://192.168.99.102:2380"],"clientURLs":["http://192.168.99.102:2379"]},{"id":"c88e2cccbb287a01","name":"node1","peerURLs":["http://192.168.99.100:2380"],"clientURLs":["http://192.168.99.100:2379"]}]}

查看當前節點是否為管理節點：

$ curl http://127.0.0.1:2379/v2/stats/leader
{"leader":"b2b0bca2e0cfcc19","followers":{"22b0de6ffcd98f00":{"latency":{"current":0.001051,"average":0.0029195000000000002,"standardDeviation":0.001646769458667484,"minimum":0.001051,"maximum":0.006367},"counts":{"fail":0,"success":10}},"c88e2cccbb287a01":{"latency":{"current":0.000868,"average":0.0022389999999999997,"standardDeviation":0.0011402923601720172,"minimum":0.000868,"maximum":0.004725},"counts":{"fail":0,"success":12}}}}

查看當前節點信息：

$ curl http://127.0.0.1:2379/v2/stats/self
{"name":"node3","id":"b2b0bca2e0cfcc19","state":"StateLeader","startTime":"2017-12-25T06:00:28.803429523Z","leaderInfo":{"leader":"b2b0bca2e0cfcc19","uptime":"36m45.45263851s","startTime":"2017-12-25T08:13:02.103896843Z"},"recvAppendRequestCnt":6,"sendAppendRequestCnt":22}

查看集群狀態：

$ curl http://127.0.0.1:2379/v2/stats/store
{"getsSuccess":9,"getsFail":4,"setsSuccess":9,"setsFail":0,"deleteSuccess":3,"deleteFail":0,"updateSuccess":0,"updateFail":0,"createSuccess":7,"createFail":0,"compareAndSwapSuccess":0,"compareAndSwapFail":0,"compareAndDeleteSuccess":0,"compareAndDeleteFail":0,"expireCount":0,"watchers":0}

當然也可以通過 API 添加和刪除集群成員。

4. API 說明和 etcdctl 命令說明

etcd REST API 說明（v2 版本）：

命令 說明
curl -L http://127.0.0.1:2379/version 查看版本
curl http://127.0.0.1:2379/v2/keys/message -XPUT -d value="Hello world" 添加鍵值
curl http://127.0.0.1:2379/v2/keys/message 獲取鍵值
curl http://127.0.0.1:2379/v2/keys/message -XPUT -d value="Hello etcd" 更新鍵值
curl http://127.0.0.1:2379/v2/keys/message -XDELETE 刪除鍵值
curl http://127.0.0.1:2379/v2/keys/foo -XPUT -d value=bar -d ttl=5 添加 TTL 鍵值（過期時間）
curl http://127.0.0.1:2379/v2/keys/foo 獲取 TTL 鍵值
curl http://127.0.0.1:2379/v2/keys/foo -XPUT -d value=bar -d ttl= -d prevExist=true 更新 TTL 鍵值
curl http://127.0.0.1:2379/v2/keys/foo?wait=true
curl http://127.0.0.1:2379/v2/keys/foo -XPUT -d value=bar
curl 'http://127.0.0.1:2379/v2/keys/foo?wait=true&waitIndex=7'
curl http://127.0.0.1:2379/v2/keys/queue -XPOST -d value=Job1
curl -s 'http://127.0.0.1:2379/v2/keys/queue?recursive=true&sorted=true'
curl http://127.0.0.1:2379/v2/keys/dir -XPUT -d ttl=30 -d dir=true
curl http://127.0.0.1:2379/v2/keys/dir -XPUT -d ttl=30 -d dir=true -d prevExist=true
curl 'http://127.0.0.1:2379/v2/keys/dir?wait=true'
curl http://127.0.0.1:2379/v2/keys/dir -XPUT -d dir=true 創建目錄
curl http://127.0.0.1:2379/v2/keys/foo_dir/foo -XPUT -d value=bar 在目錄下添加鍵值
curl http://127.0.0.1:2379/v2/keys/?recursive=true 獲取目錄下的鍵值
curl 'http://127.0.0.1:2379/v2/keys/foo_dir?dir=true' -XDELETE 刪除目錄
curl http://10.0.0.10:2379/v2/members 查看集群成員
curl http://10.0.0.10:2379/v2/members -XPOST -H "Content-Type: application/json" -d '{"peerURLs":["http://10.0.0.10:2380"]}' 添加集群成員
curl http://10.0.0.10:2379/v2/members/272e204152 -XDELETE 刪除集群成員
curl http://10.0.0.10:2379/v2/members/272e204152 -XPUT -H "Content-Type: application/json" -d '{"peerURLs":["http://10.0.0.10:2380"]}' 更新集群成員

更多 API 請查看：etcd API 和 Members API

etcdctl 命令說明：

命令 說明
etcdctl set key value 添加鍵值
etcdctl get key 獲取鍵值
etcdctl update key value 更新鍵值
etcdctl rm key 刪除鍵值
etcdctl mkdir dirname 添加目錄（不存在的話創建）
etcdctl setdir 添加目錄（都創建）
etcdctl updatedir 更新目錄
etcdctl rmdir 刪除目錄
etcdctl ls 列出目錄
etcdctl watch 監控鍵值
etcdctl exec-watch 監控鍵值（執行命令）
etcdctl list 查看集群成員
etcdctl member add 添加集群成員
etcdctl remove 移除集群成員

參考資料：


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