Docker Swarm負載均衡模式

Docker Swarm負載均衡策略

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1. 負載方式

• ingress network: docker swarm 供外部系統訪問容器訪問（原生支持，詳情看vip方式演示）,依賴docker swarm 默認overlay類型的ingress網絡
• VIP: 同網絡內容器之間的服務通過VIP實現負載均衡
• DNSRR: 同網絡容器之間的服務通過DNS實現負載均衡

2. 環境準備

4臺虛擬機：可使用docker-machine快速創建3臺包含docker環境的虛擬機

sample@debian:~$ docker-machine ls
NAME       ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER      ERRORS
manager    -        virtualbox   Running   tcp://192.168.99.100:2376           v19.03.12   
worker-1   -        virtualbox   Running   tcp://192.168.99.101:2376           v19.03.12   
worker-2   -        virtualbox   Running   tcp://192.168.99.103:2376           v19.03.12   
worker-3   -        virtualbox   Running   tcp://192.168.99.104:2376           v19.03.12   

3. VIP負載均衡

1. 登錄docker swarm管理機: docker-machine ssh manager
2. 創建overlay網絡：docker network create --driver overlay vip-overlay
3. 創建nginx服務：docker service create --name vip-nginx -p 80:80 --replicas 3 --network vip-overlay nginx
4. 創建nginx訪問客戶端容器：docker service create --name vip-debian --network vip-overlay yangzhiwei256/debian sleep 3000
5. 查看nginx服務部署節點信息：docker service ps vip-nginx

docker@manager:~$ docker service ps vip-nginx
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
othtk3grnnj9        vip-nginx.1         nginx:latest        manager             Running             Running 21 minutes ago                       
kkrxqfw6vuy9        vip-nginx.2         nginx:latest        worker-3            Running             Running 21 minutes ago                       
7nxlitp39kws        vip-nginx.3         nginx:latest        worker-1            Running             Running 21 minutes ago                       

6. 修改nginx歡迎頁(3個節點容器) 路徑：/usr/share/nginx/html/index.html

修改manager節點index頁面

• 登錄manager節點：docker-machine ssh manager
• 查看容器信息：docker ps
• 登錄容器: docker exec -it <容器ID> /bin/bash
• 修改index.html: echo manager > /usr/share/nginx/html/index.html
• 其他worker-1、worker-3 重複上述流程

7. ingress network 訪問(外部系統訪問)

• 隨便登錄一臺可訪問docker-machine節點的服務器
• 服務訪問，查看負載均衡效果
• 注意：每個docker swarm 服務節點都內置loadbalancer模塊，都可實現負載均衡訪問, 實際部署考慮單點故障問題，部署服務節點上層需加nginx網關，實現雙重負載保證高可用

sample@debian:~$ curl 192.168.99.100
worker-1
sample@debian:~$ curl 192.168.99.100
worker-3
sample@debian:~$ curl 192.168.99.100
manager
sample@debian:~$ curl 192.168.99.101
manager
sample@debian:~$ curl 192.168.99.101
worker-3
sample@debian:~$ curl 192.168.99.101
worker-1

8. vip方式訪問

• 查看網絡（manager節點）

docker@manager:~$ docker network ls                                                                                                                         
NETWORK ID          NAME                DRIVER              SCOPE
09e9cfc71ee7        bridge              bridge              local
66534a0da6cc        docker_gwbridge     bridge              local
a77be4ecae73        host                host                local
i5tgmrizq64n        ingress             overlay             swarm
6468096b83b4        none                null                local
qhmc36orimf8        vip-overlay         overlay             swarm

• 查看虛擬IP

docker@manager:~$ docker service inspect -f '{{json .Endpoint.VirtualIPs}}' vip-nginx
[{"NetworkID":"i5tgmrizq64ns0zyogh4he6u8","Addr":"10.0.0.56/24"},{"NetworkID":"qhmc36orimf87frdhxnee3ikv","Addr":"10.0.2.19/24"}]

注意：這裏有2個網絡根據networkID判斷，i5tgmrizq64ns0zyogh4he6u8對比網絡列表是docker swarm默認給外部系統訪問的負載網絡，我們使用的網絡爲vip-overlay，即vip爲10.0.2.19/24

• 通過vip訪問(同網絡容器內部訪問)

1. 登錄vip-debian：docker exec -it <vip-debian容器id> /bin/bash
2. vip服務訪問

docker@worker-2:~$ docker ps
CONTAINER ID        IMAGE                         COMMAND             CREATED             STATUS              PORTS               NAMES
08f862098d8d        yangzhiwei256/debian:latest   "sleep 3000"        48 seconds ago      Up 47 seconds                           vip-debian.1.7xfros0di1wogel0bzi2pk9pd
docker@worker-2:~$ docker exec -it 08f862098d8d /bin/bash                                                                                                   
root@08f862098d8d:/# curl 10.0.2.19
manager
root@08f862098d8d:/# curl 10.0.2.19
worker-1
root@08f862098d8d:/# curl 10.0.2.19
worker-3

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4. dnsrr負載均衡

1. 登錄docker swarm管理機: docker-machine ssh manager
2. 創建overlay網絡：docker network create --driver overlay dnsrr-overlay
3. 創建nginx服務：docker service create --name dnsrr-nginx --replicas 3 --network dnsrr-overlay --endpoint-mode dnsrr --publish published=81,target=80,protocol=tcp,mode=host nginx
4. 創建debian服務：docker service create --name dnsrr-debian --network dnsrr-overlay yangzhiwei256/debian sleep 3000
5. 修復服務節點nginx index.html，步驟同vip操作
6. 效果演示

• 登錄dnsrr-debian容器內部
• DNS服務訪問

root@d269da355467:/# curl dnsrr-nginx:80
worker-2
root@d269da355467:/# curl dnsrr-nginx:80
worker-3
root@d269da355467:/# curl dnsrr-nginx:80
worker-1