在今天的帖子中，我们将探讨原因，然后针对升级 Windows 10 后Web应用程序返回HTTP 错误 503^{(HTTP Error 503)}和WAS 事件 5189的问题提供解决方案。^{(WAS event 5189)}

Web应用程序HTTP 错误 503^{(HTTP Error 503)}和WAS事件 5189

如果您的计算机运行的是启用了Internet 信息服务 (IIS) 的 Windows 10 或 Windows Server 2016，并且^{(Windows 10)}您升级^{(Windows Server 2016)}到较新版本的Windows 10或Windows Server 2016，则某些 Web 应用程序可能无法启动，而是，他们可能会抛出以下错误消息：

Service Unavailable

HTTP Error 503. The service is unavailable.

此外，如果您看到Event Log，您将看到以下消息：

WAS事件 5189：Windows Process Activation Service未能为应用程序池“< DefaultAppPool >”生成应用程序池配置文件。错误类型为“0”。要解决此问题，请确保 applicationhost.config 文件正确并重新提交上次所做的配置更改。数据字段包含错误号。

Web应用程序HTTP 错误 503^{(HTTP Error 503)}和WAS事件 5189的原因

发生此错误的原因是 Windows激活 服务^(Service)( WAS ) 在典型操作期间为以下文件夹中的每个IIS应用程序池创建了一个临时配置文件。

C:\inetpub\temp\appPools

在初始升级阶段，Windows Update会扫描现有文件夹和文件（在Windows文件夹之外）并记录升级后要恢复的路径。但是，因为配置文件是临时的，所以当WAS停止时它们会被删除。

在Windows 更新^{(Windows Update)}的下一阶段，这些先前扫描的文件和文件夹将被复制到临时升级位置。升级 Windows后，Windows更新^{(Windows Update)}会创建一个符号链接，指向复制到临时升级位置的每个文件夹，然后再尝试将这些文件和文件夹还原到其原始位置。

但是，由于这些临时配置文件不再存在，Windows Update不会删除符号链接。

当WAS尝试作为IIS工作进程启动时，由于符号链接，它不会创建临时文件夹来写入配置。因此，Http.Sys返回HTTP 503错误。

如何解决Web应用程序HTTP 错误 503^{(HTTP Error 503)}和WAS事件 5189

为解决此问题，微软^(Microsoft)建议手动删除Windows Update创建的^{(Windows Update)}符号链接（符号链接可以像普通文件一样删除）。为此，请按照下列步骤操作。

以提升模式打开命令提示符^{(Open Command Prompt in elevated mode)}，复制并粘贴下面的命令，然后按 Enter^(Enter)：

net stop WAS /y
rmdir /s /q C:\inetpub\temp\appPools
net start W3SVC

希望这篇文章有帮助！

Web apps HTTP Error 503 and WAS event 5189 on Windows 10

In today’s post, we will explore the cause and then provide the solυtions to the issue of Web applications returning HTTP Error 503 and WAS event 5189, after you upgrade Windows 10.

Web apps HTTP Error 503 & WAS event 5189

If you have a computer that is running Windows 10 or Windows Server 2016 that has Internet Information Services (IIS) enabled, and you upgrade to a newer version of Windows 10 or Windows Server 2016, then some web applications may not start, but instead, they may throw up the following error message:

Service Unavailable

HTTP Error 503. The service is unavailable.

Moreover, if you see the Event Log, you will see the following message:

WAS event 5189: The Windows Process Activation Service failed to generate an application pool config file for application pool ‘<DefaultAppPool>’. The error type is ‘0’. To resolve this issue, please ensure that the applicationhost.config file is correct and recommit the last configuration changes made. The data field contains the error number.

Cause of Web apps HTTP Error 503 and WAS event 5189

This error can occur because the Windows Activation Service (WAS) creates a temporary configuration file for each IIS application pool in the folder below during typical operation.

C:\inetpub\temp\appPools

During an initial upgrade phase, Windows Update scans the existing folders and files (outside the Windows folder) and records their paths to be restored after the upgrade. However, because the configuration files are temporary, they are deleted when WAS is stopped.

In the next phase of Windows Update, these previously scanned files and folders are copied to a temporary upgrade location. After Windows is upgraded, Windows Update creates a symbolic link to each folder that was copied to a temporary upgrade location before it tries to restore these files and folders to their original location.

However, because these temporary configuration files no longer exist, Windows Update does not remove the symbolic links.

When WAS tries to start as an IIS worker process, it does not create a temporary folder to write the configuration because of the symbolic links. Therefore, Http.Sys returns an HTTP 503 error.

How to resolve Web apps HTTP Error 503 and WAS event 5189

To resolve this problem, Microsoft recommends to manually delete the symbolic links (Symbolic links can be deleted the same as regular files) that are created by Windows Update. To do this, follow these steps.

Open Command Prompt in elevated mode, copy and paste the command below and hit Enter:

net stop WAS /y
rmdir /s /q C:\inetpub\temp\appPools
net start W3SVC

Hope this post helps!

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