Iis ошибка http 503 услуга недоступна

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:\Windows\System32\InetSrv\appcmd.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.

HTTP errors usually come in the form of status codes which are standard response codes that help you identify the cause of the problem given by a website server when either a web page or other resource fails to load properly while online.

Whenever you get an HTTP status code, it comes with the code itself, and the corresponding explanation such as HTTP error 503: The service is unavailable.

Something else you may want to keep in mind is that each of these codes, also known as browser errors, Internet error codes or Internet connection errors have its groups.

What is the HTTP error 503?

The HTTP 503 error falls under the 5xx server error group of HTTP status codes. They usually indicate that the web page or resource request is understood by the server, but the latter cannot fill it for one reason or another.

However, the HTTP error or status codes shouldn’t be confused with Device Manager errors or system error codes, because the latter is associated with different errors and meanings altogether.

When you get HTTP error 503, this usually points to the website’s server, which may have been compromised by an overload (temporarily) or it is too busy, or there’s some ongoing such as scheduled maintenance.

Fortunately, although this error comes up often, there are fairly quick solutions to fix the issue and get the website back online.

What is HTTP error 503 and how can I fix it?

1. Preliminary checks
2. Close your proxy server
3. Start the destination application pool
4. Change Load User Profile
5. Change Identity in Application Pool

1. Preliminary checks

Whether the issue is with the server or your computer, there are some things you can try and check before fixing HTTP error 503: The service is unavailable. You could start by retrying the URL from the address bar by reloading or refreshing the page.

You can also restart your modem and router, then restart your computer or device – this is especially so if you see the ‘service unavailable – DNS failure’ message. If this doesn’t fix the error 503 DNS issue, pick new DNS servers and change them on your PC or router.

Check with the website itself directly for assistance as they may be aware of the error 503, so they may let you know if it is an issue that’s with everyone, not just you. Sometimes waiting it out is the easiest fix to this error.

• ALSO READ: 4 best browsers with built-in VPN you should use today

2. Close your proxy server

Perhaps you use a VPN or a proxy server, in which case, you need to check whether the connection is working the way it should, or properly. If the proxy server is down, then you may end up getting the HTTP error 503: The service is unavailable message.

This usually happens with free proxy servers, but if you do not use a proxy server, you can disable it and then try to open the website that is showing the HTTP error 503 the service is unavailable.

3. Start the destination application pool

If the application pool of the corresponding web application is stopped, or disabled, it causes the website to show HTTP error 503: The service is unavailable.

Additionally, any misconfiguration in the application pool or site settings can cause an error on the site. Process crashes also happen due to incorrect application logic.

Sometimes the user account related to the user identity of an application pool can be locked or has an expired password or even inadequate privileges which tamper with the functioning of the website.

If the application pool runs out of RAM or other resources, it can crash and lead to HTTP error 503, plus server migrations also lead to such errors.

If HTTP error 503 the service is unavailable is caused by a stopped application pool, starting it would resolve the issue.

• Click Start
• In the search bar, type Windows Features
• Select Turn Windows Features on or off

• Locate Internet Information Services and check the box – this will install everything you need to use IIS

• Go to Control Panel

• Select View By and click Large Icons
• Click Administrative Tools

• Find IIS Manager and double-click on it

• Select Application Pools node

• Right-click on DefaultAppPool to check the status. If it is stopped, start it. If it is running, restart it and see if HTTP error 503 the service is unavailable is gone.

• ALSO READ: 3 best browsers with VPN that don’t slow down Internet connection

4. Change Load User Profile

If the problem is the DefaultAppPool, change the ‘Load User Profile’ to false by doing the following:

• Go to Control Panel
• Select View By and click Large Icons
• Click Administrative Tools

• Find IIS Manager and double click on it

• Select Application Pools node

• Click on DefaultAppPool to select or highlight it

• On the right pane, select Advanced settings

• Find Process Model

• Go to Load User Profile

• Change from True to False

5. Change Identity in Application Pool

• Go to Control Panel
• Select View By and click Large Icons
• Click Administrative Tools
• Find IIS Manager and double-click on it
• Select Application Pools node

• Find the correct Application Pool for your website and click on it
• Click Advanced Settings

• Under Process Model, select Identity and change it, then enter a new user and password

• Click on your Application Pool again and select Recycle to restart it.

1. Reload the website
2. Restart your modem and your computer
3. Clear the browser cache
4. Check your proxy settings
5. Restart the DefaultAppPool 

• What does service temporarily unavailable mean?

The error message Service temporarily unavailable indicates the server is not available either due to overloading issues or scheduled maintenance work. This is only a temporary issue, the service should get back online once the problem has been solved.

How can I fix error 503 on specific services?

1. Fix Tachiyomi HTTP error 503

This error affects Manga fans since Tachiyomi is a popular Manga reader for Android. PC users can also use this app with the help of an emulator or a bootable USB device. Here’s how to fix error 503 on Tachiyomi:

1. Update the app, and make sure you’re using the latest version.
2. Reset your Internet connection, and restart your modem and computer.
3. Go back to the chapter menu, reload a new chapter and resume reading.
4. Open a manga from the catalog throwing error 503. Click on the menu and select the option that allows you to open it in the browser. Close the browser and the source should be fixed now.

2. Fix HTTP error 503 the service is unavailable in IIS

To fix error 503 on IIS, you can do so through the built-in Application Pool. IIS stands for Information System Security and can be easily modified through the following steps.

1. Enable IIS

1. Press the Windows Key and type windows features in the search box.
2. Click on the result to open the Windows Features tab.
3. Check the box next to Internet Information Services to enable it.

2. Start the Application Pool

1. Press the Windows Key and type control panel.
2. Click on the result to open Control Panel.
3. Select Administrative Tools from the list.
4. Find IIS Manager and click on it.
5. Click on View Application Pools from the actions tab.

3. Change the AppPool username and password

1. Go to Server, select the Application Pools and select the Application Pool of your website.
2. Go to Advanced Settings and select Identity.
3. Enter a new username and password, click on your Application Pool again.
4. Select Recycle to restart it.

4. Tweak the Load User Profile

1. Open the Advanced Settings of the DefaultAppPool.
2. Change the Load User Profile option to false as shown at step 4.

5. Delete the URL ACL

If the URL’s ACL is reserver somewhere else in the system, you’re bound to get error 503. Here’s how to fix that:

1. Open the console command and enter the netsh http show urlacl command to dump all URL ACLs.
2. If the command returns the URL that triggered error 503, delete it using the netsh http delete urlacl url=[Insert URL] command.

3. Fix urllib.error.httperror: http error 503: service unavailable

Here’s what you can do to fix urllib 503 errors:

1. Reset your Internet connection. Or connect to a different network (eg: temporarily switch to your mobile hotspot).
2. Replace urllib by curl

4. Fix www.netflix.com is currently unable to handle this request. HTTP error 503

We’re sure one of these solutions will help you fix the problem:

1. Try a different Internet connection if available.
2. Make sure your firewall settings are not blocking Netflix.
3. Sign in to your Netflix account using another device.
4. Clear your browser’s cache and cookies.

You may also want to try the solutions listed in this Netflix site error troubleshooting guide.

5. Fix Subsonic HTTP error 503

To fix error 503 on Subsonic, follow these steps:

1. Clean your Subsonic database. But first, do keep a copy of your database folder. Then, open the subsonic.data file and deleted all the media entries. Keep only the settings.
2. Reinstall the player.

Did any of these solutions help fix HTTP error 503? Let us know by leaving a comment in the section below.

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”.

See how we help web hosting companies

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.

var google_conversion_label = «owonCMyG5nEQ0aD71QM»;

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%\System32\inetsrv\appcmd.exe set config /section:serverRuntime /appConcurrentRequestLimit:100000

%SystemRoot%\System32\inetsrv\appcmd.exe set config /section:system.webserver/serverRuntime /appConcurrentRequestLimit:100000

Subscribe to 4sysops newsletter!

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.