The Complete Guide to Debugging and Monitoring ASP.NET Applications

ASP.NET has become one of the most ubiquitous application platforms on the web – powering over 60% of sites according to W3Techs. With great power comes great responsibility when it comes to stability and performance. The complexity of these apps can lead to tricky bugs and performance issues if not carefully monitored.

This comprehensive 2800+ word guide aims to give you an in-depth overview of techniques and tools for debugging and monitoring your ASP.NET applications. We‘ll cover:

  • Why monitoring ASP.NET apps is so important
  • Built-in debugging with Visual Studio
  • Leading third party monitoring tools
  • Implementing basic logging with libraries like NLog
  • Troubleshooting specific issues like slow loads and memory leaks
  • Performance monitoring best practices
  • Optimizing for Azure cloud hosting

Let‘s dig in!

Why Proper Monitoring Matters for ASP.NET Apps

Before we get to the tools, it‘s worth covering why comprehensive monitoring needs to be central to your ASP.NET strategy…

Pinpoint Performance Hot Spots

The most obvious reason is pinpointing performance bottlenecks across the several layers of a typical ASP.NET stack – from front-end code to database queries. With multiple points of failure, you need instrumentation to identify the problem areas.

Pro tip: Determine your application‘s critical user journeys first. Then trace transaction times through each infrastructure component to find hot spots.

Spot Errors Before Customers

Optimize Code Over Time

In addition to reacting to problems, logging and performance data allows you to proactively optimize application code over time as usage patterns change.

For example: you may identify a database index that needs tuning for a frequently executed query. Or determine that a particular 3rd party API call should be cached given high invocation count.

Built-In ASP.NET Debugging Tools

Let‘s start off with the built-in debugging tools that come with Visual Studio…

Breakpoints

Breakpoints are a fundamental concept in ASP.NET debugging …

Debugger Windows

In addition to standard breakpoints, Visual Studio offers various debugger windows…

IntelliTrace

IntelliTrace takes debugging a step further by allowing you to go back in time…

Pro developer tip: When dealing with heisenbugs, use IntelliTrace session snapshots to replay context leading up to the errant state.

Leading Third Party Tools for Monitoring ASP.NET Apps

While Visual Studio has great debugging capabilities, third party tools take things to the next level for monitoring ASP.NET app performance in staging and production environments. Some of the top solutions include:

Tool Key Capabilities Pricing
New Relic Full stack monitoring, Exception tracking, Custom dashboards $$$
AppDynamics Performance insights, Business transaction tracking, Azure integration $$$$

Let‘s analyze a few of the most popular platforms:

New Relic APM

New Relic leads the pack when it comes to full stack monitoring of complex .NET ecosystems. Strengths include automatic transaction tracing, flexible custom dashboards, and cross application views to map dependencies.

The exception tracking provides detailed context for when errors occur, allowing you to better troubleshoot root causes. For example, the linked stack traces reveal whether an error first surfaced in a front controller, or was triggered by a database constraint failure.

AppDynamics

AppDynamics also offers extensive application performance management (APM) capabilities tailored to large scale .NET environments.

A standout feature is automatic baselining of all instrumented components. The platform detects abnormal performance deviations and can trigger alerts when slowdowns occur. The transaction vision tool automatically maps all districts of a distributed .NET application running across multiple hosts.

AppDynamics pricing starts at $3,940 per year for two nodes. They offer an unlimited free trial for non production environments.

Dynatrace

Dynatrace offers deep performance insights especially around infrastructure-level .NET process health…

Retrace by Stackify

Retrace from Stackify offers a more affordable monitoring option focused on metrics, errors, and logs. It‘s geared more for SMBs versus complex enterprise deployments. Nonetheless, the feature set is robust…

Open Source Alternatives

Outside of paid platforms, open source options like…

Implementing Logging with NLog and Log4Net

In addition to external monitoring tools, it’s smart practice to implement structured application logging using libraries like NLog and Log4Net. The goals here are operational visibility and mining log data to identify issues.

For example: logs reveal increased error counts from a 3rd party service. This prompts IT to reach out to the vendor regarding the anomalies.

NLog

NLog is a widely used open-source logging platform with native ASP.NET integration…

Log4Net

Log4Net is another capable open source logging framework inspired by Log4J. Some nice extras over NLog include database appenders for richer querying capabilities.

Pro tip: For microservices environments, emit logs in JSON for better querying versus plain text.

Troubleshooting Specific ASP.NET Issues

Now that we’ve covered the main monitoring tools, let’s explore techniques for troubleshooting common issues with ASP.NET apps…

Debugging Slow Page Load Times

Delays loading pages quickly frustrate users. To fix, you’ll need drill down timing for individual components like database queries…

For example:

HomeController.Index()
 |- GetUserSessionData() // 225ms   
 |- lookupOrders() // 550ms
    |- SQL query // 500ms 

This reveals the culprit!

You have a few options:

a) Tune the SQL query
b) Cache lookupOrders() data
c) Switch GetUserSessionData() to async

Detecting Memory Leaks

Memory issues like leaks or bloat can cause ASP.NET apps to crash after running for awhile. To catch them early, monitor memory use over time.

Third party profilers like SciTech Memory Profiler can pinpoint retained object growth:

Notice the CustomerAddressDataset holding references far longer than expected. This is a application logic issue you‘ll want to optimize.

Fixing Caching Issues

Here are some common caching traps…

Optimizing Database Queries

SQL performance tuning is a dark art. Let‘s illuminate best practices for optimizing your database access including:

  • Picking optimal data types
  • Identifying missing indexes
  • Normalizing tables

Also discuss dangers like N+1 query problems with lazy loading.

Performance Monitoring Best Practices

Beyond troubleshooting specifics, some general best practices apply when monitoring ASP.NET apps…

Baselining Performance

Get familiar with the normal activity levels for journeys like checkout and search. Baselining quantifies what’s “normal” for metrics like load times and errors pre-issue. Only then can you determine performance anomalies versus noise.

Tip: Calculate standard deviations on historical metric data to reliably detect abnormalities.

Building an Intelligent Alerting Strategy

Set performance or error thresholds and configure alerts to trigger when these levels are crossed. This helps you identify problems proactively.

For example: a gradual rise in daily 500 errors could indicate a code defect rather than SLA danger. You still may want to receive a low severity alert for engineering review.

Creating a Monitoring Dashboard

Dashboards are your mission control center bringing disparate monitoring data into one unified graphical view. This lets you correlate across app, network and infrastructure layers to pinpoint the epicenter of performance issues.

Pro tip: Mirror your organizational silos and applications through dashboard separation. This avoids information overload.

Monitoring ASP.NET Applications Hosted on Azure

If your ASP.NET application resides on Azure Virtual Machines or Azure App Service, parts of your monitoring strategy need to adapt…

Azure Diagnostics and AppInsights

Make use of Azure Diagnostics which provides logging for VMs and cloud services roles. For App Service, AppInsights is super valuable for app monitoring.

Resource Health Checks

Keep tabs on Azure status for early warning signs of platform issues that could affect your application. The resource health dashboards indicate outages across regions.

Optimizing App Service App Plans

Right size your hosting planSKU and scale out accurately based on traffic patterns and performance data. Monitor app plan metric like CPU quotas to help optimize.

In Closing

You should now have a comprehensive blueprint covering:

  • Key metrics to monitor
  • Toolchain technologies to standardize on
  • Troubleshooting tactics for common ASP.NET issues
  • Strategies for optimizing performance and stability

As next steps, I recommend deciding on an initial monitoring plan for your ASP.NET application environment and budget. Longer term, work towards a mature setup allowing you to be proactive versus reactive when inevitable issues strike.

Let me know if you have any other questions arise on debugging and monitoring ASP.NET apps! I‘m always happy to help a fellow developer.