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erlinux 完成翻译
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使用docker快速组成样品机
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========================================
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在写前，我们将看看 Node.js 样机 ** 找寻树莓派 PI Zero ** 的供应在英国三个主要销售.
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我写的代码，黑客部署到 Azure Ubuntu 虚拟机一个晚上就可以到位。Docker 和 docker-compose 工具做出调配和更新过程非常快。
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### 建立链接？
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如果您已经通过 [动手 Docker 教程指南] [1] 那么你已有在命令行建立 Docker 容器的经验。链接一个Redis 服务器计数器节点在命令行上可能是这样：
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```
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$ docker run -d -P --name redis1
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$ docker run -d hit_counter -p 3000:3000 --link redis1:redis
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```
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现在，假设应用程序中有三个等级
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- Web 前端
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- 批次层处理长时间运行的任务
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- Redis 或 MongoDB 数据库
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通过 `--link` 管理几个容器，但可能失效，可以添加多层级或容器到应用程序。
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### 键入 docker 撰写
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>Docker 撰写图标
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docker-compose 工具是标准的 docker工具箱的一部分，也可以单独下载。它提供了丰富功能，通过一个纯文本YAML文件配置所有应用程序组件。
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上述提供了一个例子：
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```
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version: "2.0"
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services:
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redis1:
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image: redis
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hit_counter:
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build: ./hit_counter
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ports:
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- 3000:3000
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```
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从Docker 1.10起，我们可以充分利用网络来帮助我们在多个主机进行扩展覆盖。在此之前，仅通过单个主机工作。“docker-compose scale” 命令可用于更多计算能力有需要时。
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>参考docker.com上关于"docker-compose"
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### 真实例子：树莓派 PI 到货通知
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>新版树莓派 PI Zero V1.3 图片提供来自Pimoroni
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树莓派 PI Zero - 巨大的轰动一个微型计算机具有一个1GHz 处理器 和 512MB 内存能够运行完整 Linux，Docker，Node.js，Ruby 和许多流行的开源工具。一个关于 PI Zero 的好消息是，成本只有5美元。这也意味着，存量迅速抢购一空。
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*如果您想尝试Docker 或集群在PI看看下面的教程。*
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>[Docker Swarm on the PI Zero][3]
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### Original site: whereismypizero.com
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I found a webpage which used screen scraping to find whether 4-5 of the most popular outlets had stock.
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- The site contained a static HTML page
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- Issued one XMLHttpRequest per outlet accessing /public/api/
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- The server issued the HTTP request to each shop and performed the scraping
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Every call to /public/api/ took 3 seconds to execute and using Apache Bench (ab) I was only able to get through 0.25 requests per second.
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### Reinventing the wheel
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The retailers didn't seem to mind whereismypizero.com scraping their sites for stock, so I set about writing a similar tool from the ground up. I had the intention of handing a much higher amount of requests per second through caching and de-coupling the scrape from the web tier. Redis was the perfect tool for the job. It allowed me to set an automatically expiring key/value pair (i.e. a simple cache) and also to transmit messages between Node processes through pub/sub.
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>Fork or star the code on Github: [alexellis/pi_zero_stock][4]
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If you've worked with Node.js before then you will know it is single-threaded and that any CPU intensive tasks such as parsing HTML or JSON could lead to a slow-down. One way to mitigate that is to use a second worker process and a Redis messaging channel as connective tissue between this and the web tier.
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- Web tier
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-Gives 200 for cache hit (Redis key exists for store)
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-Gives 202 for cache miss (Redis key doesn't exist, so issues message)
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-Since we are only ever reading a Redis key the response time is very quick.
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- Stock Fetcher
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-Performs HTTP request
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-Scrapes for different types of web stores
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-Updates a Redis key with a cache expire of 60 seconds
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-Also locks a Redis key to prevent too many in-flight HTTP requests to the web stores.
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```
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version: "2.0"
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services:
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web:
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build: ./web/
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ports:
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- "3000:3000"
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stock_fetch:
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build: ./stock_fetch/
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redis:
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image: redis
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```
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*The docker-compose.yml file from the example.*
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Once I had this working locally deploying to an Ubuntu 16.04 image in the cloud (Azure) took less than 5 minutes. I logged in, cloned the repository and typed in `docker compose up -d`. That was all it took - rapid prototyping a whole system doesn't get much better. Anyone (including the owner of whereismypizero.com) can deploy the new solution with just two lines:
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```
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$ git clone https://github.com/alexellis/pi_zero_stock
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$ docker-compose up -d
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```
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Updating the site is easy and just involves a `git pull` followed by a `docker-compose up -d` with the `--build` argument passed along.
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If you are still linking your Docker containers manually, try Docker Compose for yourself or my code below:
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>Fork or star the code on Github: [alexellis/pi_zero_stock][5]
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### Check out the test site
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The test site is currently deployed now using docker-compose.
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>[stockalert.alexellis.io][6]
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Preview as of 16th of May 2016
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----------
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via: http://blog.alexellis.io/rapid-prototype-docker-compose/
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作者：[Alex Ellis][a]
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译者：[erlinux](https://github.com/erlinux)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: http://blog.alexellis.io/author/alex/
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[1]: http://blog.alexellis.io/handsondocker
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[2]: https://docs.docker.com/compose/compose-file/
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[3]: http://blog.alexellis.io/dockerswarm-pizero/
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[4]: https://github.com/alexellis/pi_zero_stock
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[5]: https://github.com/alexellis/pi_zero_stock
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[6]: http://stockalert.alexellis.io/
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