利用 Kubernetes 部署简单的 Python 应用程序!

Kubernetes 推出已有数年(初始发行版可追溯至 2014 年 6 月),虽然其强大的功能早已为程序员社群所熟知并认可,但很多人仍然尚未使用。如果您还没有使用过 Kubernetes,这并不稀奇。我曾听闻一些开发者说过,让他们踌躇不前的原因包括:没有真正合适的指南可供使用(大量文章分散于多个网站,而不是集中于一处),或者他们对学习新事物感到畏惧。在本教程中,我将通过利用 Docker 构建 Python 应用程序并将其部署到 Kubernetes 服务这一基本理念,帮助您一定程度上化繁为简。

学习目标

完成本教程后,您将能够:

  • 通过使用 Docker 实现 Flask 应用程序容器化,并将其部署至 IBM Cloud Kubernetes Service。

前提条件

免费试用 IBM Cloud

利用IBM Cloud Lite 快速轻松地构建您的下一个应用程序。您的免费帐户从不过期,而且您会获得 256 MB 的 Cloud Foundry 运行时内存和包含 Kubernetes 集群的 2 GB 存储空间。了解所有细节并确定如何开始。如果您不熟悉 IBM Cloud,请查阅 developerWorks 上的 IBM Cloud Essentials 课程 。

为完成本教程,您需要具备以下前提条件:

  • 一个 IBM Cloud™ 帐户 -(注册免费帐户 )
  • IBM Cloud CLI
  • Docker CLI
  • Kubernetes CLI

预计花费时间

完成本教程大约需要 45 分钟。

步骤

创建 Kubernetes 集群

  • 登录 IBM Cloud Dashboard 。
  • 打开 IBM Kubernetes Service

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  • 单击 Create Cluster

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  • 选择要部署集群的区域 ( Region ),输入集群的名称 ( name ),然后单击 Create Cluster
  • 根据您的帐户( Paid 或 Free ),选择相应的集群类型。
  • 集群需要一些时间才能准备就绪(约 30 分钟)。

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  • 集群准备就绪后,单击集群名称,这样会将您重定向至包含集群和工作节点相关信息的新页面。

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  • 单击 Worker Nodes 选项卡以记录集群的公共 IP。

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实现 Flask 应用程序的容器化

  • 在项目目录中,创建名为 “Dockerfile” 的文件。 建议:将您的文件准确命名为 “Dockerfile”,而不使用其他任何字符。

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  • “Dockerfile” 用于向 Docker 指示基本镜像、所需 Docker 设置,以及为准备和启动新容器您希望已执行的命令列表。
  • 在此文件中,粘帖以下代码:

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>FROM python:2.7
LABEL maintainer=”Kunal Malhotra, kunal.malhotra1@ibm.com
RUN apt-get update
RUN mkdir /app
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
EXPOSE 5000
ENTRYPOINT [ “python” ]
CMD [ “app.py” ]
</pre>

以上 Dockerfile 代码的说明和分解

  1. 以上代码的第一部分为:

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>FROM python:2.7
</pre>

  1. 由于此 Flask 应用程序使用 Python 2.7,我们需要支持并且已安装该程序的环境。幸运的是,DockerHub 具有在 Ubuntu 之上安装的官方镜像。只需一行代码即可获取包含 Python 2.7、virtualenv 和 pip 的基本 Ubuntu 镜像。DockerHub 上有大量镜像,但只要您愿意,您也可以从全新 Ubuntu 镜像开始,并在此基础上进行构建。
  2. 让我们来看下一段代码:

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>LABEL maintainer=”Kunal Malhotra, kunal.malhotra1@ibm.com
RUN apt-get update
</pre>

  1. 记录维护程序,并更新 Ubuntu 程序包索引。命令为 RUN,此函数用于运行它后面的命令。

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>RUN mkdir /app
WORKDIR /app
COPY ./app
</pre>

  1. 现在即可将 Flask 应用程序添加到镜像中。为简便起见,将应用程序复制到 Docker 镜像上的 /app 目录下。
  2. WORKDIR 本质上是 Bash 中的 cd ,而 COPY 则会将某个目录复制到镜像中提供的目录。ADD 命令与 COPY 执行相同的操作,但它允许您从 URL 添加存储库。因此,如果您要克隆自己的 git 存储库,而不是从本地存储库进行复制(用于登台和生产目的),那么可以使用该命令。除非您有 URL,否则大部分情况下应使用 COPY。
  3. 既然我们已将存储库复制到镜像,接下来就将安装所有依赖项,代码的 requirements.txt 部分中对此进行了定义。

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>RUN pip install –no-cache-dir -r requirements.txt
</pre>

  1. 我们使用 EXPOSE 来公开用于运行 Flask 应用程序的端口 (5000)。

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>EXPOSE 5000
</pre>

  1. ENTRYPOINT 用于指定应用程序的入口点。

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>ENTRYPOINT [ “python” ]
CMD [ “app.py” ]
</pre>

从 Dockerfile 构建镜像

打开终端,并输入以下命令以从 Dockerfile 构建镜像: docker build -t <image_name>:<tag> . (注意句点,它指示我们位于应用顶层目录中)。例如: docker build -t app:latest .

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在本地运行容器并进行测试

成功构建镜像后,输入: docker run -d -p 5000:5000 app

此命令将创建一个包含镜像中所有应用程序代码和依赖项的容器,并在本地运行该容器。

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将镜像推送至 IBM Cloud Registry

  1. 从帐户仪表板转至 IBM Cloud Kubernetes Service
  2. 在左侧导航菜单中选择 Private Repositories

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  1. 安装 Container Registry 插件。
  2. ibmcloud plugin install container-registry -r Bluemix
  3. 登录到您的 IBM Cloud 帐户。
  4. ibmcloud login -a <cloud_foundary_end_point_for_the_region>
  5. 命名并创建名称空间。快速入门的其余部分都将使用此名称空间。
  6. ibmcloud cr namespace-add <namespace>
  7. 将本地 Docker 守护程序登录到 IBM Cloud Container Registry 中。
  8. ibmcloud cr login
  9. 选择存储库和用于识别镜像的标签。
  10. docker tag <image_name> <region_url>/<namespace>/<image_name>:<tag>
  11. 推送镜像。
  12. docker push <region_url>/<namespace>/<image_name>:<tag>

<tt-image data-tteditor-tag=”tteditorTag” contenteditable=”false” class=”syl1554625776221″ data-render-status=”finished” data-syl-blot=”image” style=”box-sizing: border-box; cursor: text; color: rgb(34, 34, 34); font-family: “PingFang SC”, “Hiragino Sans GB”, “Microsoft YaHei”, “WenQuanYi Micro Hei”, “Helvetica Neue”, Arial, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: block;”>[图片上传失败…(image-30aa60-1554625780286)]

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  1. 验证您的镜像是否位于专用注册表中。
  2. ibmcloud cr image-list

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为 Kubernetes 创建配置文件

将镜像成功上传至专用注册表后,转至项目目录并创建以下两个文件: Deployment.yamlservice.yaml

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《利用 Kubernetes 部署简单的 Python 应用程序!》 image

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《利用 Kubernetes 部署简单的 Python 应用程序!》 image

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  1. deployment.yaml 文件中,粘帖以下代码:

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: flask-node-deployment
spec:
replicas: 1
selector:
matchLabels:
app: flasknode
template:
metadata:
labels:
app: flasknode
spec:
containers:
– name: flasknode
image: registry.ng.bluemix.net/flask-node/app
imagePullPolicy: Always
ports:
– containerPort: 5000
</pre>

  1. service.yaml 文件中,粘帖以下代码:

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>apiVersion: v1
kind: Service
metadata:
name: flask-node-deployment
spec:
ports:

  • port: 5000
    targetPort: 5000
    selector:
    app: flasknode
    </pre>

Deployment.yaml 代码的说明和分解

  1. 创建名为 flask-node-deployment 的部署,此部署由 .metadata.name 字段来指示。
  2. 此部署会创建一个复制 pod,由 replicas 字段来指示。
  3. Selector 字段用于定义部署查找要管理的 pod 的方式。在此情况下,我们只需选择 Pod 模板中定义的一个标签即可 (app: flasknode )。但是,也可以使用更复杂的选择规则,只要 Pod 模板本身满足此规则即可。
  4. Pod 模板规范 .template.spec 指示 pod 在运行容器 flasknode,该容器运行应用专用注册表镜像。
  5. 该部署会打开 port 5000 以供 Pod 使用。

Service.yaml 代码的说明和分解

  1. Service.yaml 规范将创建名为 flask-node-deployment 的新服务对象,目标为具有 “app=flasknode” 标签的任意 Pod 上的 TCP 端口 5000。同时还会为此服务分配 IP 地址(有时称为集群 IP),供服务代理使用(请参阅下文)。将持续评估此服务的选择器,并将结果通过 POST 操作发布到同样名为 flask-node-deployment 的端点对象。
  2. 须注意,此服务可将传入端口映射到任意 targetPort。默认情况下,targetPort 将设置为与 port 字段相同的值。可能更有趣的是,targetPort 可以是字符串,表示后端 Pod 中的端口名称。分配给该名称的实际端口号可与每个后端 Pod 中的端口号不同。这就为服务部署和演变提供了诸多灵活性。例如,您可在后端软件的下一个版本中更改 Pod 公开的端口号,而无需中断客户端。

将应用程序部署至 Kubernetes

  1. 锁定要在其中工作的 IBM Cloud Kubernetes Service 区域。
  2. ibmcloud cs region-set us-south
  3. 在 CLI 中为集群设置上下文。

<pre spellcheck=”false” style=”box-sizing: border-box; margin: 5px 0px; padding: 5px 10px; border: 0px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-weight: 400; font-stretch: inherit; font-size: 16px; line-height: inherit; font-family: inherit; vertical-align: baseline; cursor: text; counter-reset: list-1 0 list-2 0 list-3 0 list-4 0 list-5 0 list-6 0 list-7 0 list-8 0 list-9 0; background-color: rgb(240, 240, 240); border-radius: 3px; white-space: pre-wrap; color: rgb(34, 34, 34); letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;”>ibmcloud cs cluster-config
cluster_kunal

export KUBECONFIG=/Users/$USER/.bluemix/plugins/container-service/clusters/< cluster_name >/< cluster_configuration_file.yaml>
</pre>

  1. 列出您的工作节点,验证您是否可以连接到自己的集群。
  2. kubectl get nodes
  3. 创建部署。
  4. kubectl create -f deployment.yaml
    原文作者:不谈风月_0eb8
    原文地址: https://www.jianshu.com/p/a386117bb83b
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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