Http error 503 the service is unavailable asp

TL;DR:

The 503 response from the IIS machine, Service Unavailable, is the result of repeated application crashes. Since the w3wp.exe worker process, created by IIS to execute a web application, is crashing frequently, the respective IIS application pool is turned off. This is a feature of IIS, at Application Pool level, called Rapid-Fail Protection. It helps prevent consuming valuable system resources creating a worker process that crashes anyway, soon after spawning.

• Evidence of repeated w3wp.exe crashes and Rapid-Fail Protection may be found in Windows Events, in the System log with Source=WAS.
• Evidence of what causes the w3wp.exe to crash may be found in Windows Events, in the Application log: second-chance crashing exceptions with w3wp.exe.

Collecting the IIS basic troubleshooting info helps expedite investigation for the root cause of application crashes. Follow the steps at http://linqto.me/iis-basic-files for instructions.
In many cases, it may be needed to collect memory dumps to study the exceptions causing the crash: see article at http://linqto.me/dumps.

If we’re looking at the reference list of responses that IIS could send, an HTTP response status 503 means Service Unavailable. In most of the cases, we have a 503.0, Application pool unavailable; and when we check the corresponding application pool, it shows “Stopped”.

Believe it or not, that is actually a feature in IIS acting: the Rapid-Fail Protection. If the hosted application is causing the crash of its executing process for 5 times in less than 5 minutes, then the Application Pool is turned off automatically. These values are the default values; but you get the point.

Img 1, Rapid-Fail Protection settings for an Application Pool

Rapid-Fail Protection

But why turning off the application pool at all? Why is IIS doing that?

You see, there is an IIS component called WAS, Windows (Process) Activation Service, that is creating and then monitoring the worker processes – w3wp.exe – for application pools. These are the IIS processes that are loading and then executing the Web apps, including the Asp.Net ones. These are the processes responding to HTTP requests.

If a worker process crashes, WAS would immediately try to create a new process for the Application Pool; because the Web apps needs to continue serving requests. But if these processes are repeatedly crashing, soon after being created, WAS is going to “say”:

I keep creating processes for this app, and they crash. It is expensive for the system to create these processes, which crash anyway. So why don’t I stop doing that, marking the Application Pool accordingly (Stopped), until the administrator is fixing the cause. Once the condition causing the crashes is removed, then the administrator may manually re-Start the application pool.

This WAS is reporting stuff in Windows Events, in the System log. So, if we open the Events Viewer, go to System log and filter by Event Sources=WAS, we may see a pattern like this:

Img 2, Windows Events by WAS while monitoring w3wp.exe

There is a pattern to look for: Usually 5 Warning events 5011, for same application pool name, within a short time frame; if the PIDs, Process ID, in the Warning events are changing, it is a sign that the previous w3wp.exe instance was “killed”, it ended for some reason:

A process serving application pool ‘BuggyBits.local’ suffered a fatal communication error with the Windows Process Activation Service. The process id was ‘6992‘. The data field contains the error number.

… and then followed by an Error event 5002 for that same application pool name:

Application pool ‘BuggyBits.local’ is being automatically disabled due to a series of failures in the process(es) serving that application pool.

This behavior – turning off the application pool – is also seen when WAS can’t start the worker process at all. For instance when the application pool identity has a wrong or non-decipherable password: WAS can’t (repeatedly) start the w3wp.exe with the custom account that was set for the application pool. In Windows Events we would see Warnings/Errors from WAS like:

Event ID 5021 when IIS/WAS starts: The identity of application pool BuggyBits.local is invalid. The user name or password that is specified for the identity may be incorrect, or the user may not have batch logon rights. If the identity is not corrected, the application pool will be disabled when the application pool receives its first request.  If batch logon rights are causing the problem, the identity in the IIS configuration store must be changed after rights have been granted before Windows Process Activation Service (WAS) can retry the logon. If the identity remains invalid after the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number.

Event ID 5057 when app is first accessed: Application pool BuggyBits.local has been disabled. Windows Process Activation Service (WAS) did not create a worker process to serve the application pool because the application pool identity is invalid.

Event ID 5059, service becomes unavailable: Application pool BuggyBits.local has been disabled. Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool.

It is HTTP.SYS, for the inquisitive

When the application pool is turned off, hence we don’t have a w3wp.exe to process on requests for it, we’re having the HTTP.SYS driver responding status 503 instead of IIS. Remember that IIS is just a user-mode service making use of the kernel-level HTTP.SYS driver?

Img 3, HTTP.SYS validates and queues requests for IIS to pick and process

With a normal, successful request, we have the IIS responding:

Img 4, Success response 200; in Response headers, the Server is IIS

But when the application pool is down, the request does not even reach IIS. The response comes from HTTP.SYS, not from the w3wp.exe:

Img 5, With a 503 Response, the Server header is HTTP.SYS

Without a w3wp.exe to process the requests which arrived for an application pool, HTTP.SYS, while acting as a proxy, basically says:

Look, dear client, I tried to relay your request to IIS, to its w3wp.exe process created to execute the called app.
But the app or its configuration is repeatedly crashing the worker process, so creation of new processes ceased.
Hence, I had no process where to relay your request; there is no service ready to process your request.

Sorry: 503, Service Unavailable.

Why is w3wp.exe worker process failing?

I think of an IIS application pool as:

• A queue for requests, in the kernel, maintained the HTTP.SYS driver; see it in a command-line console with

  netsh http show servicestate

• Settings on how to create a w3wp.exe IIS worker process and how it should behave.
  • This process will load and execute our web application, most commonly an Asp.Net/NET Framework application.

As with all applications, exceptions happen, unforeseen errors. They all start as first-chance exceptions.

• Most of the first-chance exceptions are handled and they never hurt the app or its executing process.
  They are handled either by the code of the application, or by the Asp.Net framework itself.
  • If the unhandled exception happens in the context of executing an HTTP request, the Asp.Net Framework will do its best to treat (handle) it by wrapping it and generating an error page, usually with an HTTP response status code of 500, Server-side execution error.
    The exception that was not handled by the developer’s code gets handled by the underlying framework.
• Some exceptions are unhandled, not treated by any code in the process, so they become the so-called second-chance / process-crashing exceptions.
  • When these happen, the operating system simply terminates the process that generated them; all the virtual memory of the process is flushed away into oblivion.
  • Exceptions occurring outside the context of a request processing (such as during application startup) have more chances to become second-chance, crashing exception.

Fortunately, these exceptions – first-chance or second-chance – may leave traces. The first place to look at is in the Windows Events, Application log.

As an illustration, the code of my application running in the BuggyBits.local application pool generated the following:

Img 6, First-chance exception by app in .NET Runtime

Since the exception could not be handled by the Asp.Net, it immediately became a second-chance exception, causing Windows to terminate the w3wp.exe in the same second:

Img 7, Second-chance exception crashing w3wp.exe

Pings from WAS to check on w3wp.exe

If you notice the time-stamp in the capture above, it corresponds to a Warning event from WAS in the System log, telling that the worker process did not respond (Img 2).

This response does not refer to the HTTP request/response; it refers to pings from WAS.

Remember that I said WAS is creating the worker processes, w3wp.exe, but also it monitors them. It has to know if the worker process is healthy, if it can still serve requests. Of course, WAS is not able to know everything about the health of a w3wp.exe; many things could go wrong with the code of our app. But at least it can send pings to that process.

Illustrating with the Advanced Settings of an application pool, WAS is sending pings to its instances of w3wp.exe, every 30 seconds. For each ping, the w3wp.exe (that PID) has 90 seconds to respond. If no ping response is received, WAS concludes that the process is dead: a crash or hang happened – no process thread is available to respond to the ping. Notice that we also have other time limits too that WAS is looking on.

Img 8, Setting process pings from WAS to w3wp.exe(s)

More on exceptions

It may happen that, even looking in Windows Events > Application log, we still don’t know why our w3wp.exe is crashing or misbehaving. I’ve seen cases where the exceptions are not logged in Windows Events. In such cases, look in the custom logging solution of the web application, if it has one.

Lastly, if we don’t have a clue about these exceptions, if we have no traces left, we could attach a debugger to our w3wp.exe and see what kind of exceptions happen in there. Of course, we would need to reproduce the steps triggering the bad behavior, when using the debugger.

We can even tell that debugger to collect some more context around the exceptions, not just the exceptions itself. We could collect the call stacks or memory dumps for such context.

One such debugging tool is the command-line ProcDump. It does not require an installation; you only need to run it from an administrative console.

Let’s say I put my ProcDump in E:Dumps. Before using it, I must determine the PID, Process ID of my faulting worker process w3wp.exe:

E:Dumps>C:WindowsSystem32InetSrvappcmd.exe list wp

Then, I’m attaching ProcDump to the PID, redirecting its output to a file that I can later inspect:

E:Dumps>procdump.exe -e 1 -f "" [PID-of-w3wp.exe] > ProcDump-monitoring-log.txt

If my Windows has an UI and I’m allowed to install diagnosing apps, then I prefer Debug Diagnostics. Its UI makes it easier to configure data collection, and it determines the PID of w3wp.exe itself, based on the app pool selected. Debug Diag is better suited to troubleshoot IIS applications.

Both Debug Diag and Proc Dump are free tools from Microsoft, widely used by professionals in troubleshooting. A lot of content is available on the Web on how to use these.

A natural continuation to this article is the one I wrote about exceptions, exception handling, and how to collect memory dumps to capture exceptions or performance issues:

• About exceptions and capturing them with dumps

Aside: Just in case you are wondering what I use to capture screenshots for illustrating my articles, check out this little ShareX application in Windows Store.

Cause of HTTP Error 503

HTTP Error 503 is another very common error you might face with an IIS-hosted website in addition to the 500 – Internal server error.

The primary reason for this error is a stopped or disabled application pool. The application pool is the IIS component that initiates a worker process, which then allows the web server to process incoming requests for a website. When something is wrong with the application pool, the web server throws an HTTP Error 503.

Rapid-Fail Protection

There can be various reasons for an application pool failure, such as an unhandled exception in the code, an expired password for the application pool identity, or something else. By default, IIS is configured to disable a malfunctioning application pool if its worker process faces five consecutive crashes within a period of five minutes. This setting is known as Rapid-Fail Protection, which is available under the Advanced Settings of an application pool. This is shown in the following screenshot:

• Enabled—The value True indicates that the rapid-fail protection feature is active, which is the default. Set the value to False to disable it.
• Failure Interval (minutes)—The time interval to specify the number of minutes (by default, 5) to count the failures for a process.
• Maximum Failures—The maximum number of failures that are allowed within the time interval mentioned above (by default, 5).

While troubleshooting an application pool-related problem, you can modify these parameters, if needed.

Debugging HTTP Error 503

To determine the exact reason why the application pool is disabled or stopped, open the Event Viewer, navigate to the System log, and look for error or warning events whose source is Windows Process Activation Service (WAS). WAS is responsible for starting/stopping the application pool and keeping track of worker processes in the IIS.

The following screenshot shows that the application pool is disabled because its identity is invalid:

If you couldn’t find anything in the System log, take a look in the Application log since the ASP.Net-related exceptions are logged there. As discussed above, when a worker process experiences five fatal errors or exceptions within five minutes, rapid-fail protection kicks in and automatically disables the faulting application pool.

Based on event logs, if you conclude that the reason for application pool failure is a bug in the application code, but you still want to keep the application pool running until your developer fixes it, you could temporarily adjust the behavior of rapid-fail protection, either by increasing the Maximum Failures or the Failure Interval to a higher value. You could even disable this feature by using the following PowerShell command:

(Get-IISAppPool awesomewebsite.com).failure.rapidFailProtection
Set-WebConfigurationProperty '//*[@name="awesomewebsite.com"]//failure' -Name rapidFailProtection -Value $False

Remember that the rapid-fail protection feature is there for the safety of the web server, so disabling it shouldn’t be considered a solution to the problem. Instead, fixing the underlying cause (or bug causing the behavior) in the application code is really important. Anyway, disabling it sometimes comes in handy if developers are taking longer to fix the bug; meanwhile, you want to keep the web application up and running. Once rapid-fail protection is disabled, the web server won’t disable the faulting application pool, and visitors will no longer see HTTP Error 503.

Fixing HTTP Error 503

A simple resolution for HTTP Error 503 is to start the application pool corresponding to your website. If you get an application pool identity-related error or warning, make sure the username and password for the identity are correct. If a custom username is used, make sure its password is not expired. If possible, set the password to never expire for that user.

If the application pool stops repeatedly but there is no application pool identity-related error in the system log, the issue is likely due to some fatal error or unhandled exception in the code. In that case, the application log can give you some useful insights. The following screenshot shows a typical error logged in the application log that occurred due to an unhandled exception:

If you see such errors or warnings, notify your application developers, and ask them to fix the exception. If needed, share the detailed error message recorded in the event log.

Common 503 substatus codes

The following table covers the common HTTP 503 substatus codes, along with their possible causes and troubleshooting advice:

%SystemRoot%System32inetsrvappcmd.exe set config /section:serverRuntime /appConcurrentRequestLimit:100000

%SystemRoot%System32inetsrvappcmd.exe set config /section:system.webserver/serverRuntime /appConcurrentRequestLimit:100000

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Conclusion

You can see that, like most IIS errors, HTTP Error 503 can be fixed with the help of detailed errors and failed request tracing. However, in the event of application pool-related errors, the HTTP.sys driver throws the 503.0 error because the application pool isn’t available to handle the request. Thus, the detailed error or failed request tracing rule is not even triggered. In such situations, you can rely on Windows event logs to troubleshoot.

When you host an ASP related website with a shared Windows server, you may have run into an Error 503 Service Unavailable. Actually, there may be 4 reasons for this error. We will introduce them in detail and help you to resolve this issue accordingly in the following parts. Now, please go on reading.

1. .NET CLR Version & Managed Pipeline Mode

Once your .NET CLR version is not set correct, your website couldn’t work properly. Some web-hosting providers only provide 1 dedicated application pool for each hosting account in a shared Windows server. Thus, when you run more than 1 website with different .NET framework hosted with one account, they will get conflicted with each other.

For example, you can successfully run a website named A.com when you use .NET 2.0. However, when you try running another website named B.com with .NET 4.0, it’s very likely for you to run into 503 error at A.com. This is because the operation of B.com updated the shared application pool to .NET CLR Version 4.0.

The same logic goes for Managed Pipeline Mode, which has 2 types: Integrated and Classic.

By using local or remote IIS management, you are able to open your IIS Manager and find application pool. Then click Advance Settings. Here is what you can see as it shows:

If you’re not allowed remote International Information Services management, you should go to  your WebSitePanel, find “Extensions” in “Your Site” part and pick the correct ASP.NET pipeline.

2. Enable 32-Bit Applications

This is another possible reason for Error 503, which can be found in the above placed screenshots. Here are the 3 most common reasons for this Error 503 caused by Application Pool Bit Mode setting.

• The Classic ASP site can only work in an environment with 32-bit. You’re likely to confront this error if you: run a .NET site in an environment with 64-bit and it is hosted with a Classic ASP site or run a site with 64-bit set default by us.
• Your .NET site is specifically compiled with 32-bit or 64-bit environment, but it is hosted with another mode.
• Your .NET site requires library that run with 32-bit or 64-bit environment, but it doesn’t operate that way.

3. Application_Error

A code bug may cause a site’s application pool crashed, thus resulting to Error 503. If you can change the source code, you’d better add the following logging function to Application_Error of Global.asax.cs. As thus, you’re able to find some clues in the log file if you confront this issue next time. Read the following code snippet.

protected void Application_Error(object sender, EventArgs e)

{

    string logFilePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, “logs.txt”);

    using (StreamWriter sw = new StreamWriter(logFilePath, true, System.Text.Encoding.UTF8))

    {

        sw.Write(HttpContext.Current.Error);

    }

}

4. The Limitation of Your Web Host

If 503 Error is not led by the above 3 reasons, then it may be the limitation we set that evokes. Specifically speaking, there are 2 reasons: CPU limit and Private Memory Limit. Most hosting providers have set limitation of CPU and private memory, though they may not state the fact in public. The aim for that is to avoid the server being overused by one user. If you see this issue from web host, it’s better to consider us, we normally offer good caps on our ASP.NET Hosting.

If that is the case, you can contact our technical support team for the 2 figures, and get to know the right expectation. If your site constantly occupies more than 500 MB memory or 10 percent of local server CPU, then you should optimize your codebase.

CPU Limit

The latest IIS versions permit web-hosting providers to configure the CPU limit of an application pool so that the worker process of your website is able to use a certain amount of CPU at maximum. When your site comes with a large number of traffic or confronts a complicated situation at one time, the limit will be exceeded and your website worker process will be disabled. Before the worker process is able to restarted, you may run into this error.

You are able to find CPU limit for an application pool in your local Internet Information Services as it shows below.

The above screenshot shows that once the occupation of your server CPU is up to 15 percent, the worker process of your website is disabled and will be restarted in 5 minutes. During this period, you will experience the Error 503.

Private Memory Limit

Besides CPU limit, the private memory limit may also cause the same problem as you can see in the screenshot below. It indicates that when your site uses up more than the limited maximum memory, the worker process of your site will be recycled automatically. As thus, there is an Error 503 temporarily before it is restarted.

Summary

The above 4 factors are the main reasons that lead to Service Unavailable 503 Error. If you acquire them and you can quickly find the solution to this issue. As a Microsoft certified ASP.NET hosting provider integrating each package with at least 256 MB private memory, Bisend can help you avoid this issue.

Обновлено 03.07.2020

Добрый день! Уважаемые читатели и гости одного из крупнейших IT блогов России Pyatilistnik.org. В прошлый раз мы с вами научились чинить две вещи в Windows 10, это пресловутый черный экран и ошибку запуска в приложениях из-за отсутствия библиотеки vcruntime140.dll. Двигаемся дальше и сегодня решим еще один интересный пазл с веб сервисом IIS и ошибкой «HTTP Error 503. The service is unavailable«. Думаю, что мои грабли будут вам весьма интересны.

Описание ошибки 503 на IIS

Не так давно я устанавливал отказоустойчивую службу Remote Desktop Services High Availability на базе Windows Server 2019. Сами роли установились корректно и без ошибок в мастере, я успешно создал коллекцию, опубликовал RemoteApp приложения и хотел их протестировать, но какого же было мое удивление, когда я в место привычной формы авторизации увидел ошибку:

Причины ошибки HTTP Error 503. The service is unavailable

Сразу могу сказать, что данную проблему вы можете встретить в любом продукте компании Microsoft, где в качестве веб движка используется служба IIS (Internet Information Services). Из популярных:

• RDS фермы
• Share Point
• Exchange
• Просто сайты на IIS

Сама проблема связана в связке IIS и Net.Framework. Обычно ошибка указывает на то, что веб-страница или запрос ресурса понятен серверу, но последний не может выполнить его по той или иной причине, или же из-за банальной перегрузки, когда не хватает ресурсов.

Методы устранения ошибки 503 на IIS

Сразу скажу, что вам придется в большинстве случаев попотеть, чтобы найти причину падения вашей службы, но обо всем по порядку. Из причин можно выделить:

• Отсутствие прав у учетной записи, которая запускает пул приложений
• Вы запускаете пул в режиме 32 бита
• У вас просто не работает пул приложений
• Проблема с NET.Framework
• Проблема на уровне операционной системы из-за ошибок целостности

Переустановка системы

Как бы это смешно не звучало, но в последнем случае у меня после того, как я все перепробывал чтобы устранить ошибку 503 на IIS, уже кончились идеи и я просто снес все так как система была чистая и поставил заново, но уже более свежий дистрибутив и о чудо проблема ушла.

Не знаю, в чем было дело, то ли глюки при обновлении Windows Server 2019, то ли что-то со сборкой которая у меня была, не могу точно сказать. До переустановки у меня была версия Windows 1809 (Сборка ОС 17763.1282)

После переустановки я поставил версию от июня 2020. Когда я уже в ней запускал сайт RDweb на ферме RDS, то сервис ответил корректно и HTTP Error 503 я не увидел.

Проверка работы NET.Framework

По умолчанию в Windows Server 2019 при установке добавляется NET.Framework версии 4.7. Очень часто он может быть добавлен кривовато. В случае с Remote Desktop Services мне пришлось:

• Удалить роль IIS и RDS
• Удалить компонент NET.Framework
• Скачать NET.Framework версии 4.7. Скачиваем потому, что после его удаления у вас не будет работать диспетчер серверов и установка из PowerShell.
• Установить NET.Framework версии 4.7
• Устанавливаете IIS
• Устанавливаете RDS

В результате данного шаманства в сможете запустить RDweb на вашей RDS ферме минуя ошибку «Service Unavailable: HTTP Error 503. The service is unavailable».

Но перед всеми этими рокировками я вам советую, как и в случае с зависанием пула IIS обратиться к логам и попытаться там найти, что-то что даст нам направление для поиска информации. Напоминаю посмотреть логи Windows вы можете через оснастку «Просмотр событий» или веб-сервис Windows Admin Center. Советую смотреть четыре журнала. Первые два стандартные, это «Система» и «Приложения». Например вы можете увидеть вот такое событие с предупреждением:

Из которого понятно, что у меня не запущен пул. Откройте оснастку IIS и перейдите в раздел «Пулы приложений». Далее найдите нужный, в моем примере это RDWebAccess. Как видно у него статус «Остановлено», попробуйте его запустить.

Если пул не запускается, то я вам советую активировать в просмотре событий два дополнительных журнала:

• Microsoft-Windows-IIS-Configuration/Administrative
• Microsoft-Windows-IIS-Configuration/Operational

Так же что-то полезное вы можете найти в текстовом файле располагающемся по пути:

Как видно из файла у меня был выключен пул «2020-07-01 08:34:12 ::1%0 62570 ::1%0 443 HTTP/2 GET /RDWeb 5 503 1 Disabled RDWebAccess». У вас может быть тут другая ошибка.

Вы можете выполнить в PowerShell вот такой запрос по получению информации из данного файла, только для 503 кода.

Отключение 32 битного режима на пуле IIS

В журнале Microsoft-Windows-IIS-W3SVC-WP вы можете увидеть ошибку с кодом события: 2282, где:

По умолчанию 32-разрядная поддержка отключена в пулах приложений. Если не требуется поддержка 32-разрядных, проверьте параметры каждого из пулов приложений убедитесь, что значение Разрешить 32-разрядные приложения имеет значение False.

Откройте дополнительные параметры у нужного пула, через контекстное меню.

Еще раз проверьте что параметр Enable32bitAppOnWin64 (Разрешить 32-разрядные приложения) имеет значение «False».

Проверка учетной записи от которой запускается пул

Я очень часто встречал безалаберных системных администраторов, которым было лень создавать отдельные учетные записи для каждой службы или сервиса с которой они работают. Они делали просто, запускали все из под себя с максимальными правами или для теста так делали и забывали, что так оставили. Потом с течением времени учетную запись могут отключить или сменить пароль, что сразу делает ваш пул неработоспособным, он просто не может запустить его. Исходя из этого проверьте данную ситуацию. В дополнительных параметрах найдите раздел «Удостоверение» и посмотрите от имени кого у вас запущен ваш пул, по умолчанию должна быть встроенная учетная запись «ApplicationPoolidentity».

При необходимости вы можете выбрать другую учетную запись для запуска пула. После изменения, обязательно перезапустите пул, а лучше саму службу IIS.

Отключение Load User Profile на пуле IIS

Когда пользователь входит в систему в интерактивном режиме, система автоматически загружает профиль пользователя. Если служба или приложение олицетворяет пользователя, система не загружает профиль пользователя. Поэтому служба или приложение должны загрузить профиль пользователя с помощью LoadUserProfile .

Службы и приложения, которые вызывают LoadUserProfile, должны проверить, есть ли у пользователя временный профиль. Если пользователь имеет перемещаемый профиль, указать путь к нему в качестве lpProfilePath члена PROFILEINFO.

Для IIS этот параметр указывает, должна ли служба загружать профиль пользователя для удостоверения пула приложений. Если значение этого параметра «True», то служба IIS загружает профиль пользователя для удостоверения пула приложений. Если необходимо поведение  IIS 6.0 без загрузки профиля пользователя для удостоверения пула приложений задайте значение «False«. Так, что если получаете «HTTP Error 503. The service is unavailable» и ничего не помогает, то пробуем его отключить.

Не создает временный файл конфигурации пула

Ошибку «Service Unavailable: HTTP Error 503. The service is unavailable» вы легко можете ловить из-за того, что ваш пул по какой-то причине не может создать временный файл конфигурации и об этом может свидетельствовать предупреждение в логах:

Все происходит по причине того, что служба активации Windows (WAS) создает временный файл конфигурации для каждого пула приложений IIS в папке C:inetpubtempappPools во время обычной работы.

Чтобы решить эту проблему, вручную удалите символические ссылки, созданные «Центром обновления Windows». Для этого выполните следующие действия:

• Из командной строки от имени администратора

• Из оболочки PowerShell в режиме администратора

Два сайта на 443 порту

Был интересный случай в прошлом, мне нужно было перенести один сайт с IIS на другой сервер. После переноса вместо сайта я видел уже вам известную ошибку «Service Unavailable: HTTP Error 503. The service is unavailable». Самое интересное, что ошибка была только для HTTPS, в то время как HTTP работал нормально. Напоминаю, что по умолчанию https использует порт 443, зная это я решил посмотреть, что слушает порт, можно было конечно воспользоваться утилитами netstat или TCPView, но я пошел в тот момент через PowerShell. Введите команду, чтобы посмотреть, что порт слушается.

Как видно сервер слушается.

Если вы когда-нибудь столкнетесь с такой проблемой как 503 ответ, то попробуйте остановить службу веб-публикации

И после этого опять запустить команду на прослушивание, если и в этом случае вы видите, что 443 порт ответил, то поздравляю у вас есть другой сервис мешающий IIS.

Если это сервер, который вы унаследовали, может быть нелегко определить, что прослушивает этот конкретный порт. Я установлю модуль PowerShell с именем Carbon (https://www.powershellgallery.com/packages/Carbon/) из галереи PowerShell, чтобы определить, что происходит.

Когда веб-сервер не-IIS установлен в Windows, он устанавливает ACL для порта, который будет прослушивать. Вы можете увидеть ACL, который ссылается на порт 443.

На самом деле, есть две записи для порта 443. Тот, у кого GUID все в порядке, так как он предназначен только для конкретного приложения через заголовок узла, а не по всему пространству имен.

Второе я вычислил через TCPView, это было приложение Dell EqualLogic SAN Headquarters, установленное на этом конкретном сервере, оно вызывало проблему, поэтому я решил удалить его, так как оно больше не нужно.

Хоть я и удалил Dell EqualLogic SAN Headquarters с сервера, это не удалило ACL, назначенный порту 443.

In our role as Web support engineers, we resolve and prevent service errors in both Linux and Windows servers. Recently we were contacted by a Windows server owner who was getting “HTTP Error 503. The service is unavailable” in his websites.

Upon examining the EventViewer logs, we could see the error “A process serving application pool ‘plesk(default)(4.0)(pool)’ suffered a fatal communication error with the Windows Process Activation Service”.

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Today we’ll see what causes IIS “HTTP Error 503. The service is unavailable.” error and how we resolved it.

Our Windows server experts noted that all the domains in the server were using the same application pool [ie. ‘plesk(default)(4.0)(pool)’]. In our experience handling such errors, the following causes have been noted for this error.

1. Application Pool of the corresponding Wep Application is Stopped – In an IIS server, the domains are assigned to application pools, some dedicated and some shared. If the associated application pool for a domain is in stopped or disabled state, it would cause the website to show “HTTP Error 503. The service is unavailable.” message.
2. Any misconfiguration in the application pool or site settings, such as spawning applications in 32-bit mode, that can tamper with its proper functioning, can cause error in the site. Improper IIS configuration have noted to cause the worker process to fail. Process crashes also happen due to incorrect application logic. In some cases, the web server protocol may not be enabled in the site settings, and the site can show up ‘HTTP Error 503.’
3. Issues related to the user Identity of application Pool – An application pool is associated with a user identity, which allows you to run that application pool under a unique account. This user account can get locked at times, can have its password expired, or may not have adequate privileges to run the application pool. Any of these issues can tamper with the website functioning.
4. Application pool running out of RAM or other server resources, causing it to crash, often lead to ‘HTTP Error 503.’
5. Server migrations have also seen to have caused such errors in the website, if the IIS configuration settings of two servers are not compatible with each other, which can affect domain performance.

[ You don’t have to lose your sleep over server errors. Our expert server support specialists monitor & maintain your servers 24/7/365 and keep them rock solid. ]

How to resolve IIS “HTTP Error 503. The service is unavailable.” error

To pinpoint the actual cause of the 503 error, we examine the System event logs, which gives a hint towards what is the reason for the error. Based on that, we follow various debugging methods to resolve it.

If the error is due to a stopped application pool, then usually starting it would resolve the issue. From the IIS Manager -> Application Pools node, right click on the DefaultAppPool to check the status.

On noticing that the service is stopped, we start it. If the service is running, we try restarting it and the error would be gone. But in most cases, the fix may not be as simple as that.

In cases where the application pool crashes frequently, restarting it all the time is not the right way to fix it. We monitor the server and debug further into what is causing the application pool to crash.

For websites that are resource-intense, it is always better to assign a dedicated application pool for that domain. Another aspect we check and fix the settings of application pool and site, such as enabling the relevant protocol.

One of the key issues many fail to notice, is the user identity settings. We check the account settings and password of the identity and confirm that it is working fine. If mismatch noted, we would update the settings.

However, in this specific scenario, the issue was due to inadequate permissions of the application to run, which caused the error. By reconfiguring the application pool to run with a higher privileged identity, we were able to resolve the issue.

To avoid resource crunch leading to application crashes, we also optimized the IIS server and could see improvement in the capacity to handle connections with lesser CPU usage.

[ Use your time to build your business. We’ll take care of your servers. Hire Our server experts to resolve and prevent server issues. ]

At Bobcares, our 24/7 Support Engineers constantly monitor all the services in the server and proactively audit the server for any errors or corruption in them.

With our systematic debugging approach for service or other software errors, we have been able to provide an exciting support experience to the customers.

If you would like to know how to avoid downtime for your customers due to errors or other service failures, we would be happy to talk to you.

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