上一节我们讨论了 Service部署的两种模式，global mode 和 replicated mode 。无论global mode 还是replicated mode ，副本运行在哪些节点都是由Swarm决定的。
那么作为用户我们没有可能精细控制 Service运行的位置呢？ 答案是：能 ， 使用label
过程分两步：
1、为每个node 定义label
2、设置Service运行在指定label的node上
label 可以灵活的描述node的属性，其形式是 key = value ，用户可以任意指定，例如将 swarm-worker1 作为测试环境，为其添加label env=test
host01标记为测试环境，host02标记为线上环境
root@host03:~# docker node update --label-add env=test host01 # 将host01标记为测试环境
host01
root@host03:~# docker node inspect host01 --pretty
ID: hvt2ez9e7zvqm2hz8nix1eke7
Labels:
- env=test
Hostname: host01
Joined at: 2019-05-14 03:19:30.200301075 +0000 utc
Status:
State: Ready
Availability: Active
Address: 10.12.31.211
root@host03:~# docker node update --label-add env=prod host02 # 将host02标记为线上环境
host02
root@host03:~# docker node inspect host02 --pretty
ID: asn5ufnogzkyqigk4mizatoer
Labels:
- env=prod
Hostname: host02
Joined at: 2019-05-14 03:19:34.507855133 +0000 utc
Status:
State: Ready
Availability: Active
Address: 10.12.31.212
在测试环境创建Service my_web ，副本数 3
root@host03:~# docker service create --name my_web --replicas 3 --constraint node.labels.env==test --publish 80:80 httpd
addp6i8pm0msmamq6a4oc94py
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged
root@host03:~# docker service ps my_web # 确认所有的副本都在测试环境的node上
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
63mta4uzj5kh my_web.1 httpd:latest host01 Running Running 11 seconds ago
svynuplsq5l9 my_web.2 httpd:latest host01 Running Running 11 seconds ago
y8ion2zxr2fb my_web.3 httpd:latest host01 Running Running 11 seconds ago
root@host03:~# docker service inspect my_web --pretty
ID: addp6i8pm0msmamq6a4oc94py
Name: my_web
Service Mode: Replicated
Replicas: 3
Placement:
Constraints: [node.labels.env==test]
将 my_web 的Service 从测试环境迁移到线上环境
root@host03:~# docker service update --constraint-rm node.labels.env==test my_web # 删除Service 测试环境的标签
my_web
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged
root@host03:~# docker service ps my_web
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
63mta4uzj5kh my_web.1 httpd:latest host01 Running Running 4 minutes ago
svynuplsq5l9 my_web.2 httpd:latest host01 Running Running 4 minutes ago
y8ion2zxr2fb my_web.3 httpd:latest host01 Running Running 4 minutes ago
root@host03:~# docker service update --constraint-add node.labels.env==prod my_web # 添加Service 线上环境的标签
my_web
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged
root@host03:~# docker service ps my_web
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
mj39f4gddt7g my_web.1 httpd:latest host02 Running Running 17 seconds ago
63mta4uzj5kh \_ my_web.1 httpd:latest host01 Shutdown Shutdown 18 seconds ago
r82s4x7t8cft my_web.2 httpd:latest host02 Running Running 12 seconds ago
svynuplsq5l9 \_ my_web.2 httpd:latest host01 Shutdown Shutdown 13 seconds ago
nxu3gvglcn5y my_web.3 httpd:latest host02 Running Running 8 seconds ago
y8ion2zxr2fb \_ my_web.3 httpd:latest host01 Shutdown Shutdown 9 seconds ago
label 与 global mode 组合，只收集线上环境的日志
root@host03:~# docker service create --mode global --constraint node.labels.env==prod --name monitor busybox sleep 99999
vbo0n6hgrr8qehw1kql3znk4y
overall progress: 1 out of 1 tasks
asn5ufnogzky: running [==================================================>]
verify: Service converged
root@host03:~# docker service ps monitor
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
bek7a8mt387i monitor.asn5ufnogzkyqigk4mizatoer busybox:latest host02 Running Running 24 seconds ago