motel: Emitting Traces Without a Topology File¶

2026-03-05T07:51:15Z by Showboat 0.6.1

The motel emit command generates traces from command-line arguments, without writing a topology YAML file. This is useful for quick ad-hoc testing, scripting, and CI/CD pipelines where you need well-formed OTel signals with minimal setup.

One trace, one span¶

At its simplest, emit takes a service name and operation name and produces a single trace on stdout.

motel emit --service api --operation "GET /health" --stdout 2>/dev/null | jq -r "\"operation: \(.Name)\", \"service: \(.Attributes[] | select(.Key == \"synth.service\") | .Value.Value)\", \"kind (2=SERVER): \(.SpanKind)\""

operation: GET /health
service: api
kind (2=SERVER): 2

Custom span duration¶

The default span duration is 100ms. Use --span-duration to set a specific value.

motel emit --service api --operation "GET /health" --span-duration 250ms --stdout 2>/dev/null | jq -r '"operation: \(.Name)", "has timestamps: \((.StartTime | length) > 0)"'

operation: GET /health
has timestamps: true

Attributes¶

Use --attr key=value (repeatable) to add custom string attributes to each span.

motel emit --service deploy --operation rollout --attr version=1.2.3 --attr env=prod --stdout 2>/dev/null | jq -r '[.Attributes[] | select(.Key | startswith("synth.") | not) | "\(.Key)=\(.Value.Value)"] | sort | .[]'

env=prod
version=1.2.3

Multiple traces¶

Use --count to generate multiple traces. The default rate is 10/s; override with --rate.

motel emit --service api --operation "GET /users" --count 5 --stdout 2>/dev/null | jq -rs '"traces: \([.[].SpanContext.TraceID] | unique | length)", "spans: \(length)"'

traces: 5
spans: 5

Error rate¶

Use --error-rate to inject synthetic errors. The value is a percentage (e.g. 50%) or a decimal (e.g. 0.5).

motel emit --service api --operation "GET /users" --error-rate 100% --count 3 --stdout 2>/dev/null | jq -rs '"total spans: \(length)", "errored: \([.[] | select(.Status.Code == "Error")] | length)"'

total spans: 3
errored: 3

Run statistics¶

Like motel run, emit prints a JSON stats summary to stderr when finished.

motel emit --service api --operation "GET /health" --count 3 --stdout 2>&1 >/dev/null | jq -r '"traces: \(.traces)", "spans: \(.spans)", "error_rate: \(.error_rate)"'

traces: 3
spans: 3
error_rate: 0

For multi-service topologies, call graphs, scenarios, or sustained traffic generation, use motel run with a YAML topology file.