Observability

Barbacane provides comprehensive observability features out of the box: structured logging, Prometheus metrics, and distributed tracing with OpenTelemetry support.

Logging

Structured logs are written to stdout. Two formats are available:

JSON Format (Default)

Production-ready structured JSON logs:

barbacane serve --artifact api.bca --log-format json

{"timestamp":"2024-01-15T10:30:00Z","level":"INFO","target":"barbacane","message":"request completed","trace_id":"abc123","request_id":"def456","method":"GET","path":"/users","status":200,"duration_ms":12}

Pretty Format (Development)

Human-readable format for local development:

barbacane serve --artifact api.bca --log-format pretty --log-level debug

2024-01-15T10:30:00Z INFO  barbacane > request completed method=GET path=/users status=200 duration_ms=12

Log Levels

Control verbosity with --log-level:

Level	Description
`error`	Errors only
`warn`	Warnings and errors
`info`	Normal operation (default)
`debug`	Detailed debugging
`trace`	Very verbose tracing

barbacane serve --artifact api.bca --log-level debug

Or use the RUST_LOG environment variable:

RUST_LOG=debug barbacane serve --artifact api.bca

Metrics

Prometheus metrics are exposed on the dedicated admin API port (default 127.0.0.1:8081):

curl http://localhost:8081/metrics

Available Metrics

Metric	Type	Description
`barbacane_requests_total`	counter	Total requests by method, path, status, api
`barbacane_request_duration_seconds`	histogram	Request latency
`barbacane_request_size_bytes`	histogram	Request body size
`barbacane_response_size_bytes`	histogram	Response body size
`barbacane_active_connections`	gauge	Current open connections
`barbacane_connections_total`	counter	Total connections accepted
`barbacane_validation_failures_total`	counter	Validation errors by reason
`barbacane_middleware_duration_seconds`	histogram	Middleware execution time
`barbacane_dispatch_duration_seconds`	histogram	Dispatcher execution time
`barbacane_wasm_execution_duration_seconds`	histogram	WASM plugin execution time

Prometheus Integration

Configure Prometheus to scrape metrics:

# prometheus.yml
scrape_configs:
  - job_name: 'barbacane'
    static_configs:
      - targets: ['barbacane:8081']
    metrics_path: '/metrics'
    scrape_interval: 15s

Example Queries

# Request rate
rate(barbacane_requests_total[5m])

# P99 latency
histogram_quantile(0.99, rate(barbacane_request_duration_seconds_bucket[5m]))

# Error rate
sum(rate(barbacane_requests_total{status=~"5.."}[5m])) / sum(rate(barbacane_requests_total[5m]))

# Active connections
barbacane_active_connections

Distributed Tracing

Barbacane supports W3C Trace Context for distributed tracing and can export spans via OpenTelemetry Protocol (OTLP).

Enable OTLP Export

barbacane serve --artifact api.bca \
  --otlp-endpoint http://otel-collector:4317

Or use the environment variable:

OTEL_EXPORTER_OTLP_ENDPOINT=http://otel-collector:4317 barbacane serve --artifact api.bca

Trace Context Propagation

Barbacane automatically:

Extracts traceparent and tracestate headers from incoming requests
Generates a new trace ID if none provided
Injects trace context into upstream requests

This enables end-to-end tracing across your entire service mesh.

Span Structure

Each request creates a span tree:

barbacane.request (root span)
├── barbacane.routing
├── barbacane.validation
├── barbacane.middleware.jwt-auth.request
├── barbacane.middleware.rate-limit.request
├── barbacane.dispatch.http-upstream
├── barbacane.middleware.rate-limit.response
└── barbacane.middleware.jwt-auth.response

Span Attributes

Spans include attributes like:

http.method, http.route, http.status_code
barbacane.api, barbacane.operation_id
barbacane.middleware, barbacane.dispatcher

Integration with Collectors

Works with any OpenTelemetry-compatible backend:

Jaeger:

barbacane serve --artifact api.bca --otlp-endpoint http://jaeger:4317

Grafana Tempo:

barbacane serve --artifact api.bca --otlp-endpoint http://tempo:4317

Datadog (with collector):

# otel-collector-config.yaml
exporters:
  datadog:
    api:
      key: ${DD_API_KEY}

Production Setup

A typical production observability stack:

barbacane serve --artifact api.bca \
  --log-format json \
  --log-level info \
  --otlp-endpoint http://otel-collector:4317

Combined with:

Prometheus scraping /metrics on the admin port (default 8081)
OpenTelemetry Collector receiving OTLP traces
Grafana for dashboards and alerting
Log aggregation (Loki, Elasticsearch) ingesting stdout

Example Alert Rules

# prometheus-rules.yaml
groups:
  - name: barbacane
    rules:
      - alert: HighErrorRate
        expr: |
          sum(rate(barbacane_requests_total{status=~"5.."}[5m]))
          / sum(rate(barbacane_requests_total[5m])) > 0.01
        for: 5m
        labels:
          severity: critical
        annotations:
          summary: "High error rate detected"

      - alert: HighLatency
        expr: |
          histogram_quantile(0.99, rate(barbacane_request_duration_seconds_bucket[5m])) > 1
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "P99 latency exceeds 1 second"

What’s Next?

CLI Reference - All command-line options
Reserved Endpoints - Full metrics endpoint documentation
Spec Extensions - Barbacane spec extensions reference

Keyboard shortcuts

Barbacane Documentation