前言

docker在1.12版本之後，把swarm的功能內建到docker engine本身，因此之前使用consul等第三方服務發現和鍵值服務的方法就可以作古了。

這篇就是用docker自帶的swarm mode來進行swarm的叢集搭建。

這篇實操的主要參考是docker官網的教程。

個人建立的Docker愛好者交流QQ群：472149402，歡迎大家來此交流經驗和問題，一起成長。

架構

總共三臺虛擬機器，每一臺虛擬機器上都有docker daemon。
* 1號機manager1，IP=192.168.99.105
* 2號機worker1， IP=192.168.99.106
* 3號機worker1， IP=192.168.99.107

開始

製作1號機

$ docker-machine create -d=virtualbox manager1
Running pre-create checks...
Creating machine...
(manager1) Copying /Users/jiandaojiao/.docker/machine/cache/boot2docker.iso to /Users/jiandaojiao/.docker/machine/machines/manager1/boot2docker.iso...
(manager1) Creating VirtualBox VM...
(manager1) Creating SSH key...
 

(manager1) Starting the VM...
(manager1) Check network to re-create if needed...
(manager1) Waiting for an IP...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with
 
 boot2docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env manager1

$ docker-machine ssh manager1

$ docker swarm init --advertise-addr 192.168.99.105
Swarm initialized: current node (yyqeur66jm8vdjem5701wjqc7) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-4buvs0ux86szv2e7gc2x5i0viccmrhspfcaa40byu1xvsrjchu-6208r1mz51g3mp3nb39wgjrhp 192.168.99.105:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
yyqeur66jm8vdjem5701wjqc7 *   manager1            Ready               Active              Leader

製作2號機

$ docker-machine create -d=virtualbox worker1
Running pre-create checks...
Creating machine...
(worker1) Copying /Users/jiandaojiao/.docker/machine/cache/boot2docker.iso to /Users/jiandaojiao/.docker/machine/machines/worker1/boot2docker.iso...
(worker1) Creating VirtualBox VM...
(worker1) Creating SSH key...
(worker1) Starting the VM...
(worker1) Check network to re-create if needed...
(worker1) Waiting for an IP...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with boot2docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env worker1

$ docker swarm join --token SWMTKN-1-4buvs0ux86szv2e7gc2x5i0viccmrhspfcaa40byu1xvsrjchu-6208r1mz51g3mp3nb39wgjrhp 192.168.99.105:2377
This node joined a swarm as a worker.

下面在manager1上執行docker node ls

$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
yyqeur66jm8vdjem5701wjqc7 *   manager1            Ready               Active              Leader
tlslvt7foadfrhzqsii8huzx6     worker1             Ready               Active  

製作3號機

3號機的方法和2號機一模一樣，只要把worker1全部換成worker2。

嘗試使用swarm

釋出一個容器到叢集

$ docker service create --replicas 1 --name helloworld alpine ping docker.com
r937aud3gi8wj8ozuxmewm48n
Since --detach=false was not specified, tasks will be created in the background.
In a future release, --detach=false will become the default.

alpine的一個例項，一直去ping docker.com，命名為helloworld

如果目標機器上沒有alpine的image的話，可能service會失敗並自動去下載，等下載完，service會在此嘗試啟動。

檢視所有的service

docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
r937aud3gi8w        helloworld          replicated          1/1                 alpine:latest       

檢視名字為helloworld的service

$ docker service ps helloworld
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR                              PORTS
y5xdhd678k0f        helloworld.1        alpine:latest       manager1            Running             Running 6 minutes ago                                       
mu92gmxr9l9w         \_ helloworld.1    alpine:latest       manager1            Shutdown            Rejected 8 minutes ago   "No such image: alpine:latest@…"   

這裡可以看到有兩個helloworld，一個是running的，一個是shutdown的，都在manager1節點。其實shutdown的就是一開始manager1這個節點沒有找到alpine的image，所以失敗了。等它自動pull完alpine後，在此啟動就成功了。

inspect helloworld

$ docker service inspect --pretty helloworld

ID:     r937aud3gi8wj8ozuxmewm48n
Name:       helloworld
Service Mode:   Replicated
 Replicas:  1
Placement:
UpdateConfig:
 Parallelism:   1
 On failure:    pause
 Monitoring Period: 5s
 Max failure ratio: 0
 Update order:      stop-first
RollbackConfig:
 Parallelism:   1
 On failure:    pause
 Monitoring Period: 5s
 Max failure ratio: 0
 Rollback order:    stop-first
ContainerSpec:
 Image:     alpine:[email protected]:f006ecbb824d87947d0b51ab8488634bf69fe4094959d935c0c103f4820a417d
 Args:      ping docker.com 
Resources:
Endpoint Mode:  vip

提升helloworld服務的個數

$ docker service scale helloworld=2
helloworld scaled to 2
Since --detach=false was not specified, tasks will be scaled in the background.
In a future release, --detach=false will become the default.

$ docker service ps helloworld
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE                  ERROR                              PORTS
y5xdhd678k0f        helloworld.1        alpine:latest       manager1            Running             Running 15 minutes ago                                            
mu92gmxr9l9w         \_ helloworld.1    alpine:latest       manager1            Shutdown            Rejected 17 minutes ago        "No such image: alpine:latest@…"   
x9mimsah73qk        helloworld.2        alpine:latest       worker1             Running             Preparing about a minute ago   

刪除helloworld服務

一直ping docker.com會壓垮docker公司的吧，那麼我們把helloworld服務刪除了吧

$ docker service rm helloworld
helloworld
$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS

drain一個node

把worker1從active的狀態撤下來。這裡假設manager1和worker1和worker2都執行著helloworld的容器。

$ docker node update --availability drain worker1
worker1
$ docker service ps helloworld
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
u28niq3x2az8        helloworld.1        alpine:latest       manager1            Running             Running 5 seconds ago                        
sokgxqe620st         \_ helloworld.1    alpine:latest       worker1             Shutdown            Shutdown 5 seconds ago                       
59ps3v4t58i5        helloworld.2        alpine:latest       worker2             Running             Running 7 minutes ago                        
y2ll90r60def        helloworld.3        alpine:latest       manager1            Running             Running 9 minutes ago                        
$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
yyqeur66jm8vdjem5701wjqc7 *   manager1            Ready               Active              Leader
tlslvt7foadfrhzqsii8huzx6     worker1             Ready               Drain               
lnlcz1ec90vwzxw0p9e2ojtp4     worker2             Ready               Active  

可以發現幾件事情：
* worker1的helloworld的容器停止，並且manager1又新啟動了一個helloworld容器
* worker1的node節點狀態變成drain，從此不再接受容器任務
* 執行docker node update –availability active worker1可以使它重新回到active狀態