1. 集群维护

etcd启动参数中--initial-advertise-peer-urls --initial-cluster --initial-cluster-state --initial-cluster-token仅在创建新的member节点中使用，对于已经添加到集群中的节点而言是不生效的，因此在大部分情况，不需要修改现有etcd启动命令中的这几个参数的，同理这个参数也不能代表集群中节点的真实状态。集群的维护操作主要有以下几种：

  • 增加集群节点：比如从3个节点增加到5个节点，提升客户端读取性能
  • 移除集群节点：比如从5个节点减少到3个节点，提升客户端写入性能
  • 节点迁移维护：节点磁盘故障、节点配置升级、系统升级需要停服维护
  • 集群灾难恢复：多数节点不可用，需要用旧数据重新建立集群
  • etcd版本升级：需要参考官方文档，确认各个版本区别，然后逐个升级
  • etcd证书替换：证书到期后更换证书

1.1. 增加集群节点

向当前集群添加 etcd-4: https://10.4.7.123:2380和 etcd-5: https://10.4.7.125:2380，操作步骤如下：

  1. 确认当前集群成员信息，确保当前集群能正常对外提供服务
[root@duduniao etcd]# etc member list --write-out=table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 签发新节点的证书
# 重新签发server证书，因为原来的server证书不包含etcd-4和etcd-5。
# 从v3.2.0开始，每次客户端连接会自动加载server证书和peer证书，可以动态替换旧证书。
[root@duduniao ssl]# cat server.json
{
    "CN": "local-etcd.duduniao.com",
    "hosts": [
        "10.4.7.121",
        "10.4.7.122",
        "10.4.7.123",
        "10.4.7.124",
        "10.4.7.125",
        "127.0.0.1",
        "etcd-1",
        "etcd-2",
        "etcd-3",
        "etcd-4",
        "etcd-5",
        "localhost"
    ],
    "key": {
        "algo": "ecdsa",
        "size": 256
    },
    "names": [
        {
            "C": "CN",
            "L": "Shanghai",
            "ST": "Shanghai"
        }
    ]
}
[root@duduniao ssl]# rm -f server.csr server*.pem
[root@duduniao ssl]# cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=server server.json | cfssljson -bare server

# 以 etcd-4为例，签发 peer 证书
[root@duduniao ssl]# cat etcd-4.json
{
    "CN": "local-etcd-4.duduniao.com",
    "hosts": [
        "10.4.7.124",
        "etcd-4"
    ],
    "key": {
        "algo": "ecdsa",
        "size": 256
    },
    "names": [
        {
            "C": "CN",
            "L": "Shanghai",
            "ST": "Shanghai"
        }
    ]
}
[root@duduniao ssl]# cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=peer etcd-4.json | cfssljson -bare etcd-4
[root@duduniao ssl]# ll etcd-4*.pem etcd-5*.pem
-rw------- 1 root root  227 2021-10-19 23:06:14 etcd-4-key.pem
-rw-r--r-- 1 root root 1147 2021-10-19 23:06:14 etcd-4.pem
-rw------- 1 root root  227 2021-10-19 23:06:26 etcd-5-key.pem
-rw-r--r-- 1 root root 1147 2021-10-19 23:06:26 etcd-5.pem

# 下发etcd证书
[root@duduniao ssl]# ssh 10.4.7.124 "mkdir -pv /data/etcd/{ssl,data}"
mkdir: created directory '/data/etcd'
mkdir: created directory '/data/etcd/ssl'
mkdir: created directory '/data/etcd/data'
[root@duduniao ssl]# scp ca.pem etcd-4.pem etcd-4-key.pem 10.4.7.124:/data/etcd/ssl/
# 同步所有节点的server证书，这里只是为了方便管理，旧节点可以不用替换。
[root@duduniao ssl]# for i in 10.4.7.12{1..5};do echo $i ; scp server.pem server-key.pem $i:/data/etcd/ssl/ ;done
  1. 添加新节点
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member add etcd-4 --peer-urls https://10.4.7.124:2380
Member 79b3746506cf2fc1 added to cluster 23ce29301256c4ff

ETCD_NAME="etcd-4"
ETCD_INITIAL_CLUSTER="etcd-3=https://10.4.7.123:2380,etcd-4=https://10.4.7.124:2380,etcd-1=https://10.4.7.121:2380,etcd-2=https://10.4.7.122:2380"
ETCD_INITIAL_ADVERTISE_PEER_URLS="https://10.4.7.124:2380"
ETCD_INITIAL_CLUSTER_STATE="existing"

[root@duduniao etcd]# etc member list --write-out=table  # 当前状态是未启动
+------------------+-----------+--------+-------------------------+-------------------------+------------+
|        ID        |  STATUS   |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+-----------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 |   started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| 79b3746506cf2fc1 | unstarted |        | https://10.4.7.124:2380 |                         |      false |
| bbd6739258f69625 |   started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd |   started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+-----------+--------+-------------------------+-------------------------+------------+

# 查看任意一台节点的etcd日志：
Oct 19 15:17:05 ubuntu-1804-121 etcd[23741]: {"level":"warn","ts":"2021-10-19T15:17:05.569Z","caller":"rafthttp/probing_status.go:68","msg":"prober detected unhealthy status","round-tripper-name":"ROUND_TRIPPER_RAFT_MESSAGE","remote-peer-id":"79b3746506cf2fc1","rtt":"0s","error":"dial tcp 10.4.7.124:2380: connect: connection refused"}
Oct 19 15:17:05 ubuntu-1804-121 etcd[23741]: {"level":"warn","ts":"2021-10-19T15:17:05.569Z","caller":"rafthttp/probing_status.go:68","msg":"prober detected unhealthy status","round-tripper-name":"ROUND_TRIPPER_SNAPSHOT","remote-peer-id":"79b3746506cf2fc1","rtt":"0s","error":"dial tcp 10.4.7.124:2380: connect: connection refused"}
  1. 启动新节点(etcd-4)
[root@duduniao etcd]# cat etcd-4.service
[Unit]
Description=Etcd Server
After=network.target
After=network-online.target
Wants=network-online.target
Documentation=https://github.com/coreos

[Service]
Type=notify
WorkingDirectory=/data/etcd
Environment=ETCD_NAME="etcd-4"
Environment=ETCD_INITIAL_CLUSTER="etcd-3=https://10.4.7.123:2380,etcd-4=https://10.4.7.124:2380,etcd-1=https://10.4.7.121:2380,etcd-2=https://10.4.7.122:2380"
Environment=ETCD_INITIAL_ADVERTISE_PEER_URLS="https://10.4.7.124:2380"
Environment=ETCD_INITIAL_CLUSTER_STATE="existing"

ExecStart=/usr/local/bin/etcd \
  --listen-peer-urls https://10.4.7.124:2380 \
  --listen-client-urls https://10.4.7.124:2379,https://127.0.0.1:2379 \
  --advertise-client-urls https://10.4.7.124:2379 \
  --initial-cluster-token etcd-cluster-1 \
  --client-cert-auth \
  --cert-file ssl/server.pem \
  --key-file ssl/server-key.pem \
  --trusted-ca-file ssl/ca.pem \
  --peer-client-cert-auth \
  --peer-trusted-ca-file ssl/ca.pem \
  --peer-cert-file ssl/etcd-4.pem \
  --peer-key-file ssl/etcd-4-key.pem \
  --data-dir data \
  --snapshot-count 50000 \
  --auto-compaction-retention 1 \
  --auto-compaction-mode periodic \
  --max-request-bytes 10485760 \
  --quota-backend-bytes 8589934592
Restart=always
RestartSec=15
LimitNOFILE=65536
OOMScoreAdjust=-999

[Install]
WantedBy=multi-user.target

[root@duduniao etcd]# scp etcd-4.service 10.4.7.124:/lib/systemd/system/etcd.service
[root@duduniao etcd]# scp etcd-v3.5.1-linux-amd64/etcd* 10.4.7.124:/usr/local/bin/
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl daemon-reload && systemctl enable etcd && systemctl start etcd"

[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.124:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.124:2379 | 79b3746506cf2fc1 |   3.5.1 |   20 kB |     false |      false |         2 |         76 |                 76 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.124:2379 member list  --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| 79b3746506cf2fc1 | started | etcd-4 | https://10.4.7.124:2380 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 添加etcd-5

重复操作步骤3和步骤4即可.

[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.125:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.125:2379 | d0756e0778ff59b4 |   3.5.1 |   20 kB |     false |      false |         2 |         78 |                 78 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.124:2379 member list  --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| 79b3746506cf2fc1 | started | etcd-4 | https://10.4.7.124:2380 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
| d0756e0778ff59b4 | started | etcd-5 | https://10.4.7.125:2380 | https://10.4.7.125:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+

1.2. 移除集群节点

当集群中，需要缩减集群规模，需要移除现有的节点。如从5节点缩减至3节点，操作方式如下：

  1. 检查集群状态
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list  --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| 79b3746506cf2fc1 | started | etcd-4 | https://10.4.7.124:2380 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
| d0756e0778ff59b4 | started | etcd-5 | https://10.4.7.125:2380 | https://10.4.7.125:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 移除节点
# 移除etcd-5
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member remove d0756e0778ff59b4
Member d0756e0778ff59b4 removed from cluster 23ce29301256c4ff
# 移除etcd-4
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member remove 79b3746506cf2fc1
Member 79b3746506cf2fc1 removed from cluster 23ce29301256c4ff

[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list  --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 停止移除节点上的etcd服务
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl stop etcd && systemctl disable etcd"
[root@duduniao etcd]# ssh 10.4.7.125 "systemctl stop etcd && systemctl disable etcd"

1.3. 节点迁移维护

如果只是当前节点升级配置、服务器重启等操作，直接停服后操作即可，无需特殊处理。针对节点数据磁盘故障、或者当前节点数据迁移到新的节点上的两种场景，有两种解决方案：

  • 按照1.2 方式移旧节点，再按照 1.1 方式新增节点，如果新旧节点IP不变，则不需要签发新的证书
  • 如果数据较大(大于50MB)且旧节点数据未损坏，可用迁移节点方式

这里针对需要进行数据迁移的场景进行演示，迁移etcd-3节点到 10.4.7.124：

+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.123:2380 | https://10.4.7.123:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 模拟etcd-3故障
root@ubuntu-1804-123:~# systemctl stop etcd
  1. 迁移 10.4.7.123 上的etcd数据到 10.4.7.124
[root@duduniao etcd]# ssh 10.4.7.123 "cd /data/etcd && tar -zcf etcd-3.tar.gz data"
[root@duduniao etcd]# scp 10.4.7.123 /data/etcd/etcd-3.tar.gz ./

[root@duduniao etcd]# scp etcd-3.tar.gz 10.4.7.124:/tmp/ 
[root@duduniao etcd]# ssh 10.4.7.124 "rm -fr /data/etcd/data ; mkdir -pv /data/etcd/ssl ; tar -xf /tmp/etcd-3.tar.gz -C /data/etcd && rm -f /tmp/etcd-3.tar.gz && ls -l /data/etcd"
  1. 生成 10.4.7.124 上的etcd server证书和peer证书

参考 1.1 添加新节点中证书签发步骤，最终结果如下：

[root@duduniao etcd]# ssh 10.4.7.124 "ls -l /data/etcd/ssl"
total 20
-rw-r--r-- 1 root root 1387 Oct 19 15:31 ca.pem
-rw------- 1 root root  227 Oct 19 15:31 etcd-3-key.pem
-rw-r--r-- 1 root root 1147 Oct 19 15:31 etcd-3.pem
-rw------- 1 root root  227 Oct 19 15:37 server-key.pem
-rw-r--r-- 1 root root 1245 Oct 19 15:37 server.pem
  1. 更新集群中的member成员信息
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member update 4fe2b98ed7b794f7 --peer-urls="https://10.4.7.124:2379"
Member 4fe2b98ed7b794f7 updated in cluster 23ce29301256c4ff

# client URL需要启动后etcd进程后才能更新
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.124:2379 | https://10.4.7.123:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
  1. 启动新节点的 etcd 服务
# /lib/systemd/system/etcd.service
[Unit]
Description=Etcd Server
After=network.target
After=network-online.target
Wants=network-online.target
Documentation=https://github.com/coreos

[Service]
Type=notify
WorkingDirectory=/data/etcd
Environment=ETCD_NAME="etcd-3"

ExecStart=/usr/local/bin/etcd \
  --listen-peer-urls https://10.4.7.124:2380 \
  --listen-client-urls https://10.4.7.124:2379,https://127.0.0.1:2379 \
  --advertise-client-urls https://10.4.7.124:2379 \
  --initial-cluster-token etcd-cluster-1 \
  --client-cert-auth \
  --cert-file ssl/server.pem \
  --key-file ssl/server-key.pem \
  --trusted-ca-file ssl/ca.pem \
  --peer-client-cert-auth \
  --peer-trusted-ca-file ssl/ca.pem \
  --peer-cert-file ssl/etcd-3.pem \
  --peer-key-file ssl/etcd-3-key.pem \
  --data-dir data \
  --snapshot-count 50000 \
  --auto-compaction-retention 1 \
  --auto-compaction-mode periodic \
  --max-request-bytes 10485760 \
  --quota-backend-bytes 8589934592
Restart=always
RestartSec=15
LimitNOFILE=65536
OOMScoreAdjust=-999

[Install]
WantedBy=multi-user.target
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl start etcd && systemctl enable etcd"

# 此时集群中的etcd节点 client URL已经发生了变化
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.124:2379 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+

[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.124:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.124:2379 | 4fe2b98ed7b794f7 |   3.5.1 |   20 kB |     false |      false |         2 |        135 |                135 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+

1.4. 集群灾难恢复

etcd集群选择leader时，是少数服从多数，因此不会出现脑裂问题。当集群中的大部分节点不可用时，集群无法对外提供正常的服务，此时需要尽快启动不可用节点，只要节点数据超过半数，集群状态会自动恢复：

  1. 当少数节点不可用时
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.124:2379 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+

# 停止etcd-3模拟集群中少数节点故障
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl stop etcd"
# 节点状态正常
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.124:2379 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 endpoint health --write-out table
+-------------------------+--------+----------+-------+
|        ENDPOINT         | HEALTH |   TOOK   | ERROR |
+-------------------------+--------+----------+-------+
| https://10.4.7.121:2379 |   true | 6.6047ms |       |
+-------------------------+--------+----------+-------+

# 集群读写正常
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 put k1 v1
OK
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 get k1
k1
v1
  1. 模拟多数节点宕机
[root@duduniao etcd]# ssh 10.4.7.122 "systemctl stop etcd"

# 节点状态异常，集群状态异常
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 endpoint health --write-out table
{"level":"warn","ts":1634910316.3861823,"logger":"client","caller":"v3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0004308c0/10.4.7.121:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
+-------------------------+--------+-----------+---------------------------+
|        ENDPOINT         | HEALTH |   TOOK    |           ERROR           |
+-------------------------+--------+-----------+---------------------------+
| https://10.4.7.121:2379 |  false | 5.001016s | context deadline exceeded |
+-------------------------+--------+-----------+---------------------------+
Error: unhealthy cluster

# 节点读写报错
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 put k1 v1
{"level":"warn","ts":"2021-10-22T21:46:29.288+0800","logger":"etcd-client","caller":"v3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc000622540/10.4.7.121:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
Error: context deadline exceeded
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 get k1
{"level":"warn","ts":"2021-10-22T21:46:13.352+0800","logger":"etcd-client","caller":"v3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0004348c0/10.4.7.121:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
Error: context deadline exceeded
  1. 模拟多数节点顺利启动
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl start etcd"

# 集群状态和节点状态正常
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 endpoint health --write-out table
+-------------------------+--------+----------+-------+
|        ENDPOINT         | HEALTH |   TOOK   | ERROR |
+-------------------------+--------+----------+-------+
| https://10.4.7.121:2379 |   true | 6.8057ms |       |
+-------------------------+--------+----------+-------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 4fe2b98ed7b794f7 | started | etcd-3 | https://10.4.7.124:2379 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 put k1 v1
OK

考虑到一种极端情况，当大部分节点无法启动etcd，需要从快照或者历史备份中恢复数据，并组建一个新的集群：

  1. 停止大部分节点，使得集群无法对外提供服务
[root@duduniao etcd]# ssh 10.4.7.122 "systemctl stop etcd"
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl stop etcd"
  1. 从可用节点生成V3的快照，如果全部节点不可用则从etcd的数据目录下找到member/snap/db进行恢复，或者从历史备份恢复

v2版本的恢复方式和v3不太一样，可参考官方文档

[root@duduniao etcd]# ETCDCTL_API=3 etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 snapshot save snapshot.db
[root@duduniao etcd]# ll -h snapshot.db
-rw------- 1 root root 21K 2021-10-22 22:08:43 snapshot.d
  1. 停止节点上etcd进程，清理历史数据目录
[root@duduniao etcd]# ssh 10.4.7.121 "systemctl stop etcd ; mv /data/etcd/data /data/etcd/data.20211022.bak"
[root@duduniao etcd]# ssh 10.4.7.122 "systemctl stop etcd ; mv /data/etcd/data /data/etcd/data.20211022.bak"
[root@duduniao etcd]# ssh 10.4.7.124 "systemctl stop etcd ; mv /data/etcd/data /data/etcd/data.20211022.bak"

[root@duduniao etcd]# scp snapshot.db 10.4.7.121:/tmp/
[root@duduniao etcd]# scp snapshot.db 10.4.7.122:/tmp/
[root@duduniao etcd]# scp snapshot.db 10.4.7.124:/tmp/
  1. 重建集群
root@ubuntu-1804-121:~# ETCDCTL_API=3 etcdctl snapshot restore /tmp/snapshot.db --data-dir /data/etcd/data --initial-advertise-peer-urls https://10.4.7.121:2380 --initial-cluster etcd-1=https://10.4.7.121:2380,etcd-2=https://10.4.7.122:2380,etcd-3=https://10.4.7.124:2380 --initial-cluster-token etcd-cluster-1 --name etcd-1
root@ubuntu-1804-122:~# ETCDCTL_API=3 etcdctl snapshot restore /tmp/snapshot.db --data-dir /data/etcd/data --initial-advertise-peer-urls https://10.4.7.122:2380 --initial-cluster etcd-1=https://10.4.7.121:2380,etcd-2=https://10.4.7.122:2380,etcd-3=https://10.4.7.124:2380 --initial-cluster-token etcd-cluster-1 --name etcd-2
root@ubuntu-1804-124:~# ETCDCTL_API=3 etcdctl snapshot restore /tmp/snapshot.db --data-dir /data/etcd/data --initial-advertise-peer-urls https://10.4.7.124:2380 --initial-cluster etcd-1=https://10.4.7.121:2380,etcd-2=https://10.4.7.122:2380,etcd-3=https://10.4.7.124:2380 --initial-cluster-token etcd-cluster-1 --name etcd-3

root@ubuntu-1804-121:~# systemctl start etcd
root@ubuntu-1804-122:~# systemctl start etcd
root@ubuntu-1804-124:~# systemctl start etcd
# 验证集群
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 8bb2a873a59fd89b | started | etcd-3 | https://10.4.7.124:2380 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
[root@duduniao etcd]# etcdctl --cacert ssl/ca.pem --cert ssl/client.pem --key ssl/client-key.pem --endpoints https://10.4.7.121:2379 get k1
k1
v1

1.5. etcd版本升级

后续推出新版本升级了再补充

1.6. etcd证书替换

etcd的证书替换分为四种类型：

  1. server 证书更换：从v3.2.0开始，每个请求会重载证书，因此证书替换会变得非常方便
  2. peer 证书更换：从v3.2.0开始，每个请求会重载证书，因此证书替换会变得非常方便
  3. ca 证书更换: ca证书的替换会变得比较麻烦，需要停服维护，做好前期准备工作，停服时间在1分钟以内

上述的第一和第二种情况很容易处理，签发证书直接下发即可，老版本的etcd可用逐个重启服务。以下针对第三种情况进行操作：

  1. 生成新的证书
  2. 下发证书，并重启etcd
[root@duduniao etcd]# scan_host.sh cmd -h 10.4.7.121 10.4.7.122 10.4.7.124 "cp -r /data/etcd/ssl /data/etcd/ssl-20211021.bak"
[root@duduniao ssl-new]# scan_host.sh cmd -h 10.4.7.121 10.4.7.122 10.4.7.124 "mkdir /data/etcd/ssl-new"
[root@duduniao ssl-new]# scp ca.pem server.pem server-key.pem etcd-1.pem etcd-1-key.pem 10.4.7.121:/data/etcd/ssl-new/
[root@duduniao ssl-new]# scp ca.pem server.pem server-key.pem etcd-2.pem etcd-2-key.pem 10.4.7.122:/data/etcd/ssl-new/
[root@duduniao ssl-new]# scp ca.pem server.pem server-key.pem etcd-3.pem etcd-3-key.pem 10.4.7.124:/data/etcd/ssl-new/

[root@duduniao etcd]# scan_host.sh cmd -h 10.4.7.121 10.4.7.122 10.4.7.124 "systemctl stop etcd "
[root@duduniao etcd]# scan_host.sh cmd -h 10.4.7.121 10.4.7.122 10.4.7.124 "rm -fr /data/etcd/ssl ; mv /data/etcd/ssl-new /data/etcd/ssl"
[root@duduniao etcd]# scan_host.sh cmd -h 10.4.7.121 10.4.7.122 10.4.7.124 "systemctl start etcd "
[root@duduniao etcd]# etcdctl --cacert ssl-new/ca.pem --cert ssl-new/client.pem --key ssl-new/client-key.pem --endpoints https://10.4.7.121:2379 member list --write-out table
+------------------+---------+--------+-------------------------+-------------------------+------------+
|        ID        | STATUS  |  NAME  |       PEER ADDRS        |      CLIENT ADDRS       | IS LEARNER |
+------------------+---------+--------+-------------------------+-------------------------+------------+
| 8bb2a873a59fd89b | started | etcd-3 | https://10.4.7.124:2380 | https://10.4.7.124:2379 |      false |
| bbd6739258f69625 | started | etcd-1 | https://10.4.7.121:2380 | https://10.4.7.121:2379 |      false |
| c5542f3740ec56cd | started | etcd-2 | https://10.4.7.122:2380 | https://10.4.7.122:2379 |      false |
+------------------+---------+--------+-------------------------+-------------------------+------------+
[root@duduniao etcd]# etcdctl --cacert ssl-new/ca.pem --cert ssl-new/client.pem --key ssl-new/client-key.pem --endpoints https://10.4.7.121:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.121:2379 | bbd6739258f69625 |   3.5.1 |   20 kB |     false |      false |         7 |         37 |                 37 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
[root@duduniao etcd]# etcdctl --cacert ssl-new/ca.pem --cert ssl-new/client.pem --key ssl-new/client-key.pem --endpoints https://10.4.7.122:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.122:2379 | c5542f3740ec56cd |   3.5.1 |   20 kB |     false |      false |         7 |         37 |                 37 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
[root@duduniao etcd]# etcdctl --cacert ssl-new/ca.pem --cert ssl-new/client.pem --key ssl-new/client-key.pem --endpoints https://10.4.7.124:2379 endpoint status --write-out table
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|        ENDPOINT         |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.4.7.124:2379 | 8bb2a873a59fd89b |   3.5.1 |   20 kB |      true |      false |         7 |         37 |                 37 |        |
+-------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+

2. 备份和恢复

大部分etcd集群的数据都是很小的，可以考虑每个小时备份一次，只需要从一个节点进行备份即可，不需要每个节点都进行备份。数据恢复是指通过现有的快照数据，重新建立集群，备份和恢复的方式可以参考 1.4. 集群灾难恢复。

原文来自：运维渡渡鸟

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