配置docker的負載均衡
1.建立一個文件docker-compose.yml，具體內容如下：
This docker-compose.yml file tells Docker to do the following:（具體解釋如下）
Run five instances of?the image we uploaded in step 2?as a service called web, limiting each one to use, at most, 10% of the CPU (across all cores), and 50MB of RAM.
# 運行我們之前制作好放置到docker倉庫的docker 鏡像，限制每個使用的資源為10%的CPU和50MB的內存
Immediately restart containers if one fails. ?# 如果失敗快速重啟
Map port 80 on the host to web’s port 80. # 映射到外部的80端口
Instruct web’s containers to share port 80 via a load-balanced network called web net. (Internally, the containers themselves will publish to web’s port 80 at an ephemeral port.)
# 通過負載均衡分享80端口
Define the web net network with the default settings (which is a load-balanced overlay network).
#用默認的設置定義網絡
2.Run your new load-balanced app
Before we can use the docker stack deploy command we’ll first run（用doker stack deploy命令之前必須先執行下邊的命令）
[root@host1 ~]#docker swarm init
Note: We’ll get into the meaning of that command in?part 4. If you don’t run docker swarm init you’ll get an error that “this node is not a swarm manager.”
Now let’s run it. You have to give your app a name – here it is set to getstartedlab:
# 運行命令，之前要先起一個名字，這里設置的是getstartedlab
[root@host1 ~]#docker stack deploy -c docker-compose.yml getstartedlab
See a list of the five containers you just launched:
[root@host1 ~]#docker stack ps getstartedlab
You can run curl http://localhost several times in a row, or go to that URL in your browser and hit refresh a few times. Either way, you’ll see the container ID randomly change, demonstrating the load-balancing; with each request, one of the five replicas is chosen at random to respond.
# 通過網址訪問刷新，會看到頁面的容器ID 不斷的發生變化，演示著負載均衡的效果，隨機的五選一來回復
3.Scale the app（規?；瘧?）
You can scale the app by changing the replicas value in docker-compose.yml, saving the change, and re-running the docker stack deploy command:（當docker-compose.yml文件的內容發生變化時，可以通過重新執行docker stack deploy -c docker-compose.yml getstartedlab來重新部署，不需要先關閉再重新啟動）
[root@host1 ~]#docker stack deploy -c docker-compose.yml getstartedlab
Docker will do an in-place update, no need to tear the stack down first or kill any containers.
4.Take down the app
Take the app down with docker stack rm:（關閉app）
[root@host1 ~]#docker stack rm getstartedlab
It’s as easy as that to stand up and scale your app with Docker. You’ve taken a huge step towards learning how to run containers in production. Up next, you will learn how to run this app on a cluster of machines.（下一節講述如何在集群運行應用）
