When a cookie is empty and corrupt, users may run into intermittent access issues to your website. IIS may record CryptographicException (The data is invalid) error to Event Viewer for this issue. Since the issue is intermittent, there may not be a need for immediate solution. However, a root cause analysis can provide valuable information and clues to prevent future occurrences.
Here is the key part of the error message from the Application container in Event Viewer:
Event code: 3005 Event message: An unhandled exception has occurred. Trust level: Full Process name: w3wp.exe Exception type: CryptographicException Exception message: The data is invalid. at System.Security.Cryptography.ProtectedData.Unprotect(Byte encryptedData, Byte optionalEntropy, DataProtectionScope scope) at System.IdentityModel.ProtectedDataCookieTransform.Decode(Byte encoded)
High CPU load is one of the most common issues web servers struggle with. There could be several root causes such as deadlocks, insufficient hardware, high traffic, poor coding. In this post, I will explain the reason and solution for a high CPU load caused by an object which is not thread-safe.
This issue may surface in many ways. One if them is -obviously- high resource utilization. You can monitor the resource usage in Task Manager, Resource Monitor or Performance Monitor.
Before we go further, let’s remember what the thread safety is:
Thread safety is a computer programming concept applicable in the context of multi-threaded programs. A piece of code is thread-safe if it only manipulates shared data structures in a manner that guarantees safe execution by multiple threads at the same time.
High CPU load in Performance Monitor and Event Viewer
The Performance Monitor chart below shows that the CPU load is around 80% (red solid line). It also demonstrates how the error count (brown dashed line) increases in parallel to request total (green dashed line).
This issue may appear as error or warning messages in Event Viewer that seems unrelated to CPU load at first sight. The message below is recorded in the System container of Event Viewer and it mentions unresponsive application pool which points out high CPU load issue.
Event ID: 5010 (Warning)
A process serving application pool “X” failed to respond to a ping. The process id was “1234”
Root cause of the high CPU load
As I mentioned in the beginning of the post, there could be a variety of reasons why a web server suffers from high CPU load. In this scenario, the reason is that using an instance of a non-thread-safe object multiple times. More specifically, using the same HttpClient instance from different threads increases the CPU usage.
In official documentation for HttpClient, it is recommended to use only one instance of this object:
HttpClient is intended to be instantiated once and re-used throughout the life of an application. Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. This will result in SocketException errors.
Visual Studio provides all-in-one experience for software developers. From coding to testing, it makes IT professional’s lives easier. Error messages like “Socket Exception: No such host is known” refers to certain issues in the code or configuration of the application. In this post, I will explain the root cause and solution for this error message.
This error message may appear in may forms. Here is one of them:
System.Net.Sockets.SocketException: No such host is known
In some cases, you may see the exception code 0x80004005 along with the error message above. In addition, if you are receiving ThreadAbortException, check this post out.
The root cause of the “No such host is known” error
In the scenario I tested and in the online posts I reviewed, the root cause was the same: DNS name resolution failure. Basically, your application tries to call an API URL or to connect to a service but it is not able to find the hostname or your server is not able to do DNS lookup for that hostname.
Since it is an issue with DNS name resolution, nothing you do with Visual Studio, IIS, TFS or Windows will help fixing this issue. However, a simple code update may do the magic!
The solution is fairly simple. Make sure your server is able to access to the DNS server and your DNS server is able to lookup the hostname in your code. Follow the steps below to troubleshoot and solve this issue.
In Command Prompt, run ipconfig /all. This will list the IP addresses of the DNS server you use. Try to ping them. Additionally, check with a colleague to see he or she has the same configuration
Run nslookup. Enter the hostname in your code. Make sure the DNS server is able to lookup this hostname.
Make sure there is no typo or white spaces in the hostname. If you are getting this input from a JSON call or configuration file, it is possible that the source string and the variable you have are different.