docker1.12版本的swarm集群特性
docker1.12版本之后集成了swarm模块，直接使用dokcer-engin就能很方便地创建一个docker集群，不用再像以前那样第三方配置。环境：
manager/node1:swarm_node1
node2: swarm_node2
1：首先在各节点上安装最新版dokcer
# curl -fsSL https://test.docker.com/ | sh
# docker -v
Docker version 1.12.0-rc4, build e4a0dbc
2:在node1上初始化一个swarm集群
swarm_node1:
# docker swarm init
No --secret provided. Generated random secret:
dm18yjza2eb00wsbbk1hleq8q
Swarm initialized: current node (4abdf6see9vqr83emyhdf529s) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --secret dm18yjza2eb00wsbbk1hleq8q \
--ca-hash sha256:cda112fa02a5c17850852b4d65366bb8484bcb204a46ae97063648b5545e277d \
192.168.1.131:2377
3:根据提示，把node2添加进swarm集群
swarm_node2:
#docker swarm join --secret dm18yjza2eb00wsbbk1hleq8q --ca-hash sha256:cda112fa02a5c17850852b4d65366bb8484bcb204a46ae97063648b5545e277d192.168.1.131:2377
This node joined a Swarm as a worker. 提示节点添加成功。
4:查看集群状态，需在管理节点node1上：
# docker swarm inspect
[
{
"ID": "0kx8spry37citf16ty448y65e",
"Version": {
"Index": 11
},
"CreatedAt": "2016-08-05T02:09:17.248225691Z",
"UpdatedAt": "2016-08-05T02:09:17.861408652Z",
"Spec": {
"Name": "default",
"AcceptancePolicy": {
"Policies": [
{
"Role": "worker",
"Autoaccept": true,
"Secret": "$2a$10$oqvNfMPFiKIrEvYrZENRGOxsJly8.QnzNZ7XDKkP20MN8027N3gxm"
},
{
"Role": "manager",
"Autoaccept": false,
"Secret": "$2a$10$oqvNfMPFiKIrEvYrZENRGOxsJly8.QnzNZ7XDKkP20MN8027N3gxm"
}
]
},
"Orchestration": {
"TaskHistoryRetentionLimit": 10
},
"Raft": {
"SnapshotInterval": 10000,
"LogEntriesForSlowFollowers": 500,
"HeartbeatTick": 1,
"ElectionTick": 3
},
"Dispatcher": {
"HeartbeatPeriod": 5000000000
},
"CAConfig": {
"NodeCertExpiry": 7776000000000000
}
}
}
]
# docker node ls
ID HOSTNAME MEMBERSHIPSTATUS AVAILABILITY MANAGER STATUS
4abdf6see9vqr83emyhdf529s * swarm_node1 Accepted Ready Active Leader
cs95yh0c4c0fo892996m5wozk swarm_node2 Accepted Ready Active 可以看到各节点的状态(Active)和角色(Leader)等。
5:service管理
1.12新增了service命令，用于管理一个服务。例如我们需要一个test的服务，需要两个容器，运行ping的命令：
# docker service create --name test --replicas 2 centos ping 127.0.0.1
bgach5ib1uoubo2ljarrx48xu
# docker service ls
ID NAME REPLICAS IMAGE COMMAND
bgach5ib1uou test 0/2 centos ping 127.0.0.1
# docker service tasks test
ID NAME SERVICE IMAGE LAST STATE DESIRED STATE NODE
5rw3fr6xdl3kojhh28qzg8yos test.1 test centos Preparing 21 seconds ago Running swarm_node1
1l9siyzbflljowd543c5ehdil test.2 test centos Preparing 21 seconds ago Running swarm_node2 --repicas 2指定了服务的个数为2，可以看到在node1,node2上分别跑了一个容器，组成了一个test的服务。
6：service的错误恢复与容器迁移。
service的新特性最大的亮点是错误迁移与恢复的机制，如果某一个节点上的docker服务下线了，或者服务器出现故障，swarm集群会检测service是否发生变动，如果发现某个节点故障，会在另外的节点恢复容器，以保证service的完整。
比如，这时，我让swarm_node2退出swarm集群：
# docker swarm leave
Node left the swarm. 再查看test服务：
# docker service tasks test
ID NAME SERVICE IMAGE LAST STATE DESIRED STATE NODE
5rw3fr6xdl3kojhh28qzg8yos test.1 test centos Preparing 5 minutes ago Running swarm_node1
9pzt555uzeswik14lj6bp96hf test.2 test centos Preparing about a minute ago Running swarm_node1 可以看到test这个服务依旧保持了2个容器，而且由于node2已经下线，容器全部迁移到了node1。
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