A trace records the complete path of a request through a distributed system — from the first service it enters to the final response. ARMS collects this data so you can see every service call, its timing, and whether it succeeded.
Benefits
In a distributed system, a single request typically touches multiple services. When a request times out, fails, or throws an exception, pinpointing the root cause requires visibility into the full call chain. Traces provide that visibility:
Troubleshooting: Traces expose the complete request path and the execution status of every service involved, so you can isolate failures fast.
Performance optimization: Per-span durations reveal execution bottlenecks, giving you a precise target for optimization.
System monitoring: Traces provide real-time visibility into system behavior, helping O&M engineers assess service health and resource utilization.
Key concepts
Trace
A trace captures the complete execution of a request — from the moment it enters the system to its final response. For example, a user action that triggers calls across three microservices produces one trace covering the entire journey, including every remote procedure call (RPC) and database query.
Each trace is a tree of spans. ARMS assigns every trace a unique trace ID that persists across all services for the duration of the request. All spans belonging to the same request share this trace ID, so you can query every related span in one place when debugging.
The span at the root of the tree — the root span — has no parent. It marks the start of the trace. Every other span has a parent span ID that links it back to the span that triggered it, forming the call hierarchy.
Span
A span is the basic unit of a trace. It represents a single logical operation — such as a method call, a program block invocation, an RPC, or a database query.
Each span records:
A unique span ID
Start and end timestamps
A parent span ID (absent on the root span)
Spans nest inside one another to form the trace tree, mirroring the actual service call hierarchy.