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What is distributed tracing?

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The advent of modern cloud and microservices architectures has given rise to simple, independently deployable services that can help reduce costs while increasing availability and throughput. These movements have made individual services easier to understand. But they've also made overall systems more difficult to reason about and debug.

In monolithic architectures, we've gotten used to debugging with call stacks. Call stacks are brilliant tools for showing the flow of execution (Method A called Method B, which called Method C), along with details and parameters about each of those calls. This technique is great for monoliths or services running on a single process. But how do we debug when the call is across a process boundary, not simply a reference on the local stack?

That's where distributed tracing comes in.

Distributed tracing is the equivalent of call stacks for modern cloud and microservices architectures, with the addition of a simplistic performance profiler thrown in. In Azure Monitor, we provide two experiences for consuming distributed trace data. The first is our transaction diagnostics view, which is like a call stack with a time dimension added in. The transaction diagnostics view provides visibility into one single transaction/request. It's helpful for finding the root cause of reliability issues and performance bottlenecks on a per-request basis.

Azure Monitor also offers an application map view, which aggregates many transactions to show a topological view of how the systems interact. The map view also shows what the average performance and error rates are.

Enable distributed tracing

Enabling distributed tracing across the services in an application is as simple as adding the proper agent, SDK, or library to each service, based on the language the service was implemented in.

Enable via Application Insights through auto-instrumentation or SDKs

The Application Insights agents and SDKs for .NET, .NET Core, Java, Node.js, and JavaScript all support distributed tracing natively. Instructions for installing and configuring each Application Insights SDK are available for:

With the proper Application Insights SDK installed and configured, tracing information is automatically collected for popular frameworks, libraries, and technologies by SDK dependency auto-collectors. The full list of supported technologies is available in the Dependency auto-collection documentation.

Any technology also can be tracked manually with a call to TrackDependency on the TelemetryClient.

Enable via OpenTelemetry

Application Insights now supports distributed tracing through OpenTelemetry. OpenTelemetry provides a vendor-neutral instrumentation to send traces, metrics, and logs to Application Insights. Initially, the OpenTelemetry community took on distributed tracing. Metrics and logs are still in progress.

A complete observability story includes all three pillars, but currently our Azure Monitor OpenTelemetry-based exporter preview offerings for .NET, Python, and JavaScript only include distributed tracing. Our Java OpenTelemetry-based Azure Monitor offering is generally available and fully supported.

The following pages consist of language-by-language guidance to enable and configure Microsoft's OpenTelemetry-based offerings. Importantly, we share the available functionality and limitations of each offering so you can determine whether OpenTelemetry is right for your project.

Enable via OpenCensus

In addition to the Application Insights SDKs, Application Insights also supports distributed tracing through OpenCensus. OpenCensus is an open-source, vendor-agnostic, single distribution of libraries to provide metrics collection and distributed tracing for services. It also enables the open-source community to enable distributed tracing with popular technologies like Redis, Memcached, or MongoDB. Microsoft collaborates on OpenCensus with several other monitoring and cloud partners.

For more information on OpenCensus for Python, see Set up Azure Monitor for your Python application.

The OpenCensus website maintains API reference documentation for Python, Go, and various guides for using OpenCensus.

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