Exception summarization

When you're trying to generate meaningful diagnostic messages for exceptions, maintaining the inclusion of pertinent information can pose a challenge. The standard exception message often lacks critical details that accompany the exception, while invoking the Exception.ToString method yields an excess of state information.

This article relies on the Microsoft.Extensions.Diagnostics.ExceptionSummarization NuGet package.

The goal of exception summarization

Metric tags typically support a limited number of distinct values, and as such they are not suitable to represent values which are highly variable, such as the result of Exception.ToString(). An exception summary represents a low-cardinality version of an exception's information, suitable for such cases.

The goal of exception summarization is twofold:

• To reduce the cardinality associated with exception state such that exceptions can be reliably counted in metrics. This matters since metric dimensions have limited cardinality.
• To eliminate privacy-sensitive information from exception state such that some meaningful exception information can be added to logs.

Exception summarization API

The IExceptionSummarizer interface offers methods for extracting crucial details from recognized exception types, thereby furnishing a singular string that serves as the foundation for crafting top-quality diagnostic messages.

The IExceptionSummarizer.Summarize method systematically traverses the roster of registered summarizers until it identifies a summarizer capable of handling the specific exception type. In the event that no summarizer is capable of recognizing the exception type, a meaningful default exception summary is provided instead.

The result of the Summarize method returns an ExceptionSummary struct, and it contains the following properties:

• ExceptionSummary.Description: The summary description of the exception.
• ExceptionSummary.AdditionalDetails: Intended for low-level diagnostic use, this property contains additional details about the exception and has a relatively high cardinality. This property may contain privacy-sensitive information.
• ExceptionSummary.ExceptionType: The type of the exception, unless inner exceptions are present, in which case both outer and inner types are reflected.

Example exception summarization usage

The following example demonstrates how to use the IExceptionSummarizer interface to retrieve a summary of an exception.

using System.Net;
using System.Net.Sockets;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.ExceptionSummarization;

// Add exception summarization services.
var services = new ServiceCollection()
    .AddExceptionSummarizer(static builder => builder.AddHttpProvider());

var provider = services.BuildServiceProvider();

// Get the exception summarizer.
IExceptionSummarizer summarizer = provider.GetRequiredService<IExceptionSummarizer>();

// Define exceptions to summarize.
Exception[] exceptions =
[
    new OperationCanceledException("Operation cancelled..."),
    new TaskCanceledException("Task cancelled..."),
    new SocketException(10_024, "Too many sockets open..."),
    new WebException("Keep alive failure...",
        WebExceptionStatus.KeepAliveFailure)
];

foreach (var exception in exceptions)
{
    // Summarize the exception.
    ExceptionSummary summary = summarizer.Summarize(exception);

    Console.WriteLine(summary);
}

Console.ReadLine();

The preceding code:

• Instantiates a new ServiceCollection instance, chaining a call to the AddExceptionSummarizer extension method.
  • The AddExceptionSummarizer extension method accepts a delegate that is used to configure the ExceptionSummarizerBuilder instance.
  • The builder is used to add the HTTP provider, which handles exceptions of type:
    • OperationCanceledException
    • TaskCanceledException
    • SocketException
    • WebException
• Builds a new ServiceProvider instance from the ServiceCollection instance.
• Gets an instance of the IExceptionSummarizer interface from the ServiceProvider instance.
• Iterates over a collection of exceptions, calling the Summarize method on each exception and displaying the result.