.NET Continuous Profiler: Under the Hood

The Datadog .NET Profiler is a tool designed for analyzing application performance and method call stacks, focusing on runtime performance metrics such as CPU consumption, wall time duration, thrown exceptions, threads contention on locks, and memory allocation. Unlike other profiling tools that have high overhead and are best run sporadically or in non-production code, Datadog's profiler is built to run continuously on production systems with minimal impact on application performance. The .NET Profiler architecture consists of several individual profilers, each responsible for collecting data for a particular resource. Each profiler has a sampler and a provider that exposes the collected samples. An aggregator gathers these samples, and an exporter serializes them into a .pprof file, which is then uploaded to Datadog's backend for further processing and analysis. The profiler attaches metadata to each .pprof file sent to the Datadog Agent by HTTP, including process ID, host name, and runtime ID. This allows the Datadog backend to find the profiles related to a given trace or span. The tracer tells the profiler which runtime ID maps an AppDomain to which service name (DD_SERVICE), which can be set through configuration or API. Datadog's .NET continuous profiler is written in native code (C++ and Rust) that runs in the same process as the profiled application, allowing it to collect data even during the startup of a .NET application. The profiler leverages various CLR services for its implementation, depending on the version of the runtime being used. In summary, the Datadog .NET Profiler provides continuous, low-impact profiling capabilities for production applications, enabling developers to analyze and optimize their code's performance in real-world environments.