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etcd revision 测试

Oct 29, 2020 2020-10-29T16:20:00+08:00 by adream307
6 min

docker-compose

启动 etcd 集群

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docker-compose -f etcd-only.yml up -d

etcd-only.yml,设置 snapshot 为100，即每 100 个修改，产生一次 snapshot，清除 WAL

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version: '3.5'
services:
    machine-1:
        image: quay.io/coreos/etcd:v3.4.9
        hostname: machine-1
        container_name: machine-1
        command: etcd --data-dir=data.etcd --name machine-1 --initial-advertise-peer-urls http://machine-1:2380 --listen-peer-urls http://0.0.0.0:2380 --advertise-client-urls http://machine-1:2379 --listen-client-urls http://0.0.0.0:2379 --initial-cluster machine-1=http://machine-1:2380,machine-2=http://machine-2:2380,machine-3=http://machine-3:2380 --initial-cluster-state new --initial-cluster-token etcd-token-01 --snapshot-count 100
        ports:
            - 10001:2379
        networks:
            - etcd-net

    machine-2:
        image: quay.io/coreos/etcd:v3.4.9
        hostname: machine-2
        container_name: machine-2
        command: etcd --data-dir=data.etcd --name machine-2 --initial-advertise-peer-urls http://machine-2:2380 --listen-peer-urls http://0.0.0.0:2380 --advertise-client-urls http://machine-2:2379 --listen-client-urls http://0.0.0.0:2379 --initial-cluster machine-1=http://machine-1:2380,machine-2=http://machine-2:2380,machine-3=http://machine-3:2380 --initial-cluster-state new --initial-cluster-token etcd-token-01 --snapshot-count 100
        ports:
            - 10002:2379
        networks:
            - etcd-net

    machine-3:
        image: quay.io/coreos/etcd:v3.4.9
        hostname: machine-3
        container_name: machine-3
        command: etcd --data-dir=data.etcd --name machine-3 --initial-advertise-peer-urls http://machine-3:2380 --listen-peer-urls http://0.0.0.0:2380 --advertise-client-urls http://machine-3:2379 --listen-client-urls http://0.0.0.0:2379 --initial-cluster machine-1=http://machine-1:2380,machine-2=http://machine-2:2380,machine-3=http://machine-3:2380 --initial-cluster-state new --initial-cluster-token etcd-token-01 --snapshot-count 100
        ports:
            - 10003:2379
        networks:
            - etcd-net
                  
networks:
    etcd-net:
        name: etcd-net

获得节点 IP 地址

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$ IP1=$(docker exec machine-1 cat /etc/hosts | grep "machine-1" | awk '{print $1}')
$ IP2=$(docker exec machine-2 cat /etc/hosts | grep "machine-2" | awk '{print $1}')
$ IP3=$(docker exec machine-3 cat /etc/hosts | grep "machine-3" | awk '{print $1}')
$ ENDPOINTS=$IP1:2379,$IP2:2379,$IP3:2379
$ echo "endpoints : $ENDPOINTS"
endpoints : 192.168.208.2:2379,192.168.208.3:2379,192.168.208.4:2379

查看当前 revision

向etcd查询某个 key 即可获得当前 revision，因此最简单的办法就是查询一个不存在的 key。

如下所示，查询 revisiontestkey ，因为这个 key 不存在，那么只返回查询的 head, revision 就在 head 中

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$ etcdctl --endpoints=$ENDPOINTS get revisiontestkey -w json
{"header":{"cluster_id":18293669711776909085,"member_id":15078865400474202024,"revision":1,"raft_term":2}}

snapshot

进入 machine-1 观察 snapshot 文件夹

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docker exec -it machine-1 sh

观察 snapshot 文件夹

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$ ls data.etcd/member/snap -lh
total 20K
-rw------- 1 root root 20K Aug  4 07:56 db

当前 snapshot 文件夹内只有 db 文件，并未生成 snapshot

插入数据

因为 snapshot-count 这是为 100，那么插入 150 个数据，中间一定定触发 snapshot

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CNT=0
while [ $CNT -lt 150 ]; do
    etcdctl --endpoints=$ENDPOINTS put key${CNT} value${CNT}
    CNT=$[$CNT + 1]
done

插入数据后，再次查询 revision，变成了 151

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$ etcdctl --endpoints=$ENDPOINTS get revisiontestkey -w json
{"header":{"cluster_id":18293669711776909085,"member_id":8241799522139745222,"revision":151,"raft_term":2}}

再次查看 snapshot

可以观察到生成的 snapshot 文件

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$ ls data.etcd/member/snap -lh
total 56K
-rw-r--r-- 1 root root 8.9K Aug  4 08:26 0000000000000002-0000000000000065.snap
-rw------- 1 root root  40K Aug  4 08:26 db

根据 revision 查询

查询 revision 为 5 之前的所有数据

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$ etcdctl --endpoints=$ENDPOINTS get '' --prefix --rev 5    
key0
value0
key1
value1
key2
value2
key3
value3

因为snapshot-count 为 100，那么在 插入 key99 后，etcd 生成 snapshot，而 key99 对应的 revision 为 101；但是在 revision 为 101 位置触发了 snapshot 操作后依然可以查询 revision 为 5 的数据，这说明snapshot 操作仅仅删除 WAL，并不会在 revision 上做任何删除操作

压缩 revision

将 revision 压缩，意味着删除指定 revision 之前的所有数据版本信息，如下所示，删除 revision 5 之前的所有版本信息

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etcdctl --endpoints=$ENDPOINTS compaction 5

压缩后，可以列出 revision 为 5 之前的所有数据

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$ etcdctl --endpoints=$ENDPOINTS get '' --prefix --rev 5
key0
value0
key1
value1
key2
value2
key3
value3

但是没办法列出 revision 为 4 之前的所欲数据

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$ etcdctl --endpoints=$ENDPOINTS get '' --prefix --rev 4
{"level":"warn","ts":"2020-08-04T16:46:30.923+0800","caller":"clientv3/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"endpoint://client-46e1b5a7-2fa4-4079-98df-ebddbf6896fa/192.168.208.2:2379","attempt":0,"error":"rpc error: code = OutOfRange desc = etcdserver: mvcc: required revision has been compacted"}
Error: etcdserver: mvcc: required revision has been compacted

提示我们需要的版本信息已经被删除了

revision 测试

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$ etcdctl --endpoints=$ENDPOINTS get key10 -w json 
{"header":{"cluster_id":18293669711776909085,"member_id":15078865400474202024,"revision":151,"raft_term":2},"kvs":[{"key":"a2V5MTA=","create_revision":12,"mod_revision":12,"version":1,"value":"dmFsdWUxMA=="}],"count":1}

查询的 key10，返回只的 key 和 value 使用 base64 编码，可以在这个网址:https://www.base64decode.org/ 进行解码

  • create_revision 表示 key10 创建时的 revision 值;
  • mod_revision 表示 key10 最后一次修改时的 revision 值，第一次创建时，这个值就是 create_revision 的值
  • version 表示当前版本号,第一次创建时，改版本号为 1
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    {
  "key":"a2V5MTA=",
  "create_revision":12,
  "mod_revision":12,
  "version":1,
  "value":"dmFsdWUxMA=="
}

修改 key10，并再次查询 key10

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$ etcdctl --endpoints=$ENDPOINTS put key10 new_value10
OK
$ etcdctl --endpoints=$ENDPOINTS get key10 -w json
{"header":{"cluster_id":18293669711776909085,"member_id":8241799522139745222,"revision":152,"raft_term":2},"kvs":[{"key":"a2V5MTA=","create_revision":12,"mod_revision":152,"version":2,"value":"bmV3X3ZhbHVlMTA="}],"count":1}
  • create_revision 的值不变，依然为 12
  • mod_revision 变为当前最新的 revision 152
  • version 变为 2
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    {
  "key":"a2V5MTA=",
  "create_revision":12,
  "mod_revision":152,
  "version":2,
  "value":"bmV3X3ZhbHVlMTA="
}

删除所有 key 打头的数据

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$ etcdctl --endpoints=$ENDPOINTS del key --prefix -w json
{"header":{"cluster_id":18293669711776909085,"member_id":15078865400474202024,"revision":153,"raft_term":2},"deleted":150}

查询所有 key 打头的数据，因为所有的数据均被删除，所以返回的数据为空

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etcdctl --endpoints=$ENDPOINTS get key --prefix -w json
{"header":{"cluster_id":18293669711776909085,"member_id":8241799522139745222,"revision":153,"raft_term":2}}

多次修改值

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$ etcdctl --endpoints=$ENDPOINTS put key150 value150
$ etcdctl --endpoints=$ENDPOINTS put key150 new_150 -w json
{"header":{"cluster_id":18293669711776909085,"member_id":15078865400474202024,"revision":155,"raft_term":2}}
$ etcdctl --endpoints=$ENDPOINTS put key150 new_new_150 -w json
{"header":{"cluster_id":18293669711776909085,"member_id":8241799522139745222,"revision":156,"raft_term":2}}
$ etcdctl --endpoints=$ENDPOINTS put key150 new_new_new_150 -w json
{"header":{"cluster_id":18293669711776909085,"member_id":7328269484100982375,"revision":157,"raft_term":2}}

按照 revision 获得值

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$ etcdctl --endpoints=$ENDPOINTS get key150 --rev 156
key150
new_new_150
$ etcdctl --endpoints=$ENDPOINTS get key150 --rev 155
key150
new_150
$ etcdctl --endpoints=$ENDPOINTS get key150 --rev 154
key150
value150

如果某个值有多个版本，那么根据 revision 获得的值为离指定 revision 最近的的版本

关闭 etcd 集群

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docker-compose -f etcd-only.yml down
etcd
etcd
This post is licensed under CC BY 4.0 by the author.
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