Visual Tracer
The visual tracer renders request trace files as an annotated decision diagram, making it easy to see exactly which path through the HTTP state machine a given request took.
Viewing a Trace
Trace files are written by req.enableTrace(directory) — see Request Tracing for setup.
Once you have a trace file, you can map the decision sequence back to the HTTP diagram manually, or use a diagram tool with the node names as reference:
- Open the HTTP decision diagram.
- Locate the first decision in
decisions[](alwaysv3b13). - Follow each step in order — the diagram branches are labeled with the return value that leads to each path.
Interpreting Decision Names
Decision names follow the pattern v3<column><row>:
| Name | Description |
|---|---|
v3b13 | Service available? |
v3b12 | Known method? |
v3b11 | URI too long? |
v3b10 | Method allowed? |
v3c3 | Accept header present? |
v3d4 | Acceptable media type available? |
v3g7 | Resource exists? |
v3l13 | If-Modified-Since present? |
v3o18 | Conflict? |
See the full HTTP diagram for the complete node map.