【Azure 应用服务】 部署到App Service for Linux 服务的Docker 镜像，如何配置监听端口呢？

问题描述

根据以下DockerFile文件，创建了一个ASP.NET Core的 helloworld 镜像，通过监听3721端口来接受请求。

# 1. 指定编译和发布应用的镜像
FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build

# 2. 指定（编译和发布）工作目录
WORKDIR /app

# 3. 拷贝.csproj到工作目录/app，然后执行dotnet restore恢复所有安装的NuGet包
COPY *.csproj ./
RUN dotnet restore

# 4. 拷贝所有文件到工作目录(/app)，然后执行dotnet publish命令将应用发布到/app/out目录下
COPY . ./
RUN dotnet publish -c Release -o out

# 5. 编译生成Docker镜像
# 5.1.设置基础镜像
FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS runtime

# 5.2. 设置（运行）工作目录，并将发布文件拷贝到out子目录下
WORKDIR /app
COPY --from=build /app/out .

# 5.3. 利用环境变量设置ASP.NET Core应用的监听地址
ENV ASPNETCORE_URLS http://0.0.0.0:3721

# 5.4. 执行dotnet命令启动ASP.NET Core应用
ENTRYPOINT ["dotnet", "helloworld.dll"]

在本地构建镜像后，可以通过 docker run -d -p 8088:3721 --name myapp helloworldapp，指定本机8088端口映射到Docker Container中的3721端口。

但是在部署到微软云后，如何来设置映射端口呢？ 默认情况下App Service 使用的是80端口，从而导致容器启动失败。

错误日志为：

2022-06-15T08:10:50.546Z INFO - Status: Downloaded newer image for lbacrtest01.azurecr.cn/helloworldapp:v1
2022-06-15T08:10:50.587Z INFO - Pull Image successful, Time taken: 2 Minutes and 5 Seconds
2022-06-15T08:10:50.676Z INFO - Starting container for site
2022-06-15T08:10:50.676Z INFO - docker run -d --expose=80 --name lbimagetest01_0_1e3ba35e -e WEBSITES_ENABLE_APP_SERVICE_STORAGE=false -e WEBSITE_SITE_NAME=lbimagetest01 -e WEBSITE_AUTH_ENABLED=False -e PORT=80 -e WEBSITE_ROLE_INSTANCE_ID=0 -e WEBSITE_HOSTNAME=lbimagetest01.chinacloudsites.cn -e WEBSITE_INSTANCE_ID=fca8f86e2aee5216a9504a5ef5a82caeab7a80b1093c88842a262c639a933047 -e WEBSITE_USE_DIAGNOSTIC_SERVER=False lbacrtest01.azurecr.cn/helloworldapp:v1

2022-06-15T08:10:50.676Z INFO - Logging is not enabled for this container.
Please use https://aka.ms/linux-diagnostics to enable logging to see container logs here.
2022-06-15T08:11:02.091Z INFO - Initiating warmup request to container lbimagetest01_0_1e3ba35e for site lbimagetest01
2022-06-15T08:11:17.595Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 15.5042301 sec
2022-06-15T08:11:33.023Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 30.9320513 sec
2022-06-15T08:11:48.176Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 46.0847374 sec
2022-06-15T08:12:03.309Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 61.2176683 sec
2022-06-15T08:12:18.466Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 76.3745667 sec
2022-06-15T08:12:33.640Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 91.5484349 sec
2022-06-15T08:12:48.766Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 106.6748131 sec
2022-06-15T08:13:03.926Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 121.8346172 sec
2022-06-15T08:13:19.084Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 136.9925924 sec
2022-06-15T08:13:34.841Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 152.7495565 sec
2022-06-15T08:13:54.936Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 172.8446712 sec
2022-06-15T08:14:10.134Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 188.0428893 sec
2022-06-15T08:14:29.366Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 207.274851 sec
2022-06-15T08:14:44.507Z INFO - Waiting for response to warmup request for container lbimagetest01_0_1e3ba35e. Elapsed time = 222.4153247 sec
2022-06-15T08:14:52.646Z ERROR - Container lbimagetest01_0_1e3ba35e for site lbimagetest01 did not start within expected time limit. Elapsed time = 230.5552784 sec
2022-06-15T08:14:58.488Z ERROR - Container lbimagetest01_0_1e3ba35e didn't respond to HTTP pings on port: 80, failing site start. See container logs for debugging.

问题解答

在App Service中，如果要为容器暴露端口，可以使用应用配置参数 WEBSITES_PORT,  把它的值设置为DockerFile中配置的端口就行。如本示例中就配置它的值为3721.

保存后将自动重启App Service，查看Docker日志，发现 --expose的端口变为3721， Container 初始化成功并且准备接受请求。

2022-06-15T08:14:59.910Z INFO - Pulling image: lbacrtest01.azurecr.cn/helloworldapp:v1
2022-06-15T08:15:00.307Z INFO - v1 Pulling from helloworldapp
2022-06-15T08:15:00.318Z INFO - Digest: sha256:1f6d1d7452248155c22adac3007d19c59da2825d982da8383fc2cf33f80cade7
2022-06-15T08:15:00.325Z INFO - Status: Image is up to date for lbacrtest01.azurecr.cn/helloworldapp:v1
2022-06-15T08:15:00.327Z INFO - Pull Image successful, Time taken: 0 Minutes and 0 Seconds
2022-06-15T08:15:00.488Z INFO - Starting container for site
2022-06-15T08:15:00.495Z INFO - docker run -d --expose=3721 --name lbimagetest01_0_fa97e372 -e WEBSITES_ENABLE_APP_SERVICE_STORAGE=false -e WEBSITES_PORT=3721 -e WEBSITE_SITE_NAME=lbimagetest01 -e WEBSITE_AUTH_ENABLED=False -e WEBSITE_ROLE_INSTANCE_ID=0 -e WEBSITE_HOSTNAME=lbimagetest01.chinacloudsites.cn -e WEBSITE_INSTANCE_ID=fca8f86e2aee5216a9504a5ef5a82caeab7a80b1093c88842a262c639a933047 -e WEBSITE_USE_DIAGNOSTIC_SERVER=False lbacrtest01.azurecr.cn/helloworldapp:v1

2022-06-15T08:15:00.496Z INFO - Logging is not enabled for this container.
Please use https://aka.ms/linux-diagnostics to enable logging to see container logs here.
2022-06-15T08:15:04.397Z INFO - Initiating warmup request to container lbimagetest01_0_fa97e372 for site lbimagetest01
2022-06-15T08:15:05.738Z INFO - Container lbimagetest01_0_fa97e372 for site lbimagetest01 initialized successfully and is ready to serve requests.

附录：创建，推送，部署Image的命令

## 本地构建 helloworldapp 镜像文件
docker build -t helloworldapp .

## 本地运行 helloworldapp 镜像，8088端口映射容器中3721端口
docker run -d -p 8088:3721 --name myapp helloworldapp

## 登录到ACR（azure容器库）中
docker login <acrtest01>.azurecr.cn --username <testuser01>

## 与ACR关联本地镜像文件
docker tag helloworldapp:v1 <acrtest01>.azurecr.cn/helloworldapp:v1

## PUSH 镜像文件到ACR中
docker push <acrtest01>.azurecr.cn/helloworldapp:v1

参考文档：

使用自定义容器将自定义软件迁移到 Azure 应用服务：https://docs.azure.cn/zh-cn/app-service/tutorial-custom-container?pivots=container-linux#configure-app-service-to-deploy-the-image-from-the-registry