platform-observability — shared metrics + dashboard

@demystify/platform-observability (TS) · demystify-platform-observability (Py) · v0.2.0 · MIT

What it is / when to use it

The single source of truth for RED metrics across all six Demystify services. Canonical dmstfy_* metric names, a metrics registry with RED helpers, a framework-neutral /metrics handler, an offline HTML dashboard, and a bridge that turns a module's existing span instrumentation into duration metrics for free.

Leaf package: depends only on prom-client (TS) / prometheus-client (Py). Zero dependency on any module. Keyless, offline, deterministic.

Install standalone

pnpm add @demystify/platform-observability        # TS
uv add demystify-platform-observability           # Py

Canonical metric names

Defined once, shared by both languages (METRIC_NAMES / fixture-locked):

| name | type | labels | |---|---|---| | dmstfy_http_requests_total | counter | method, route, status, tenant | | dmstfy_http_request_duration_seconds | histogram | method, route, status, tenant | | dmstfy_provider_calls_total | counter | provider, model, status | | dmstfy_provider_call_duration_seconds | histogram | provider, model, status | | dmstfy_provider_cost_micro_usd_total | counter | provider, model | | dmstfy_queue_depth | gauge | queue | | dmstfy_span_duration_seconds | histogram | span, module |

Durations are seconds; cost is integer µUSD (CONVENTIONS.md §2). Buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10].

SDK usage

import {
  createMetrics, mountMetricsHono, renderDashboardHtml, spanExporterToMetrics,
} from "@demystify/platform-observability";

const metrics = createMetrics();
metrics.httpRequest("GET", "/v1/chat", 200, tenantId, 12.4);         // RED helper
metrics.providerCall("openai", "gpt-4o", "ok", 210, 1500);          // count+dur+cost
metrics.queueDepth("gateway", 7);

mountMetricsHono(app, metrics);                    // GET /metrics (Prometheus text)
setSpanExporter(spanExporterToMetrics(metrics));   // spans -> duration histogram
const html = renderDashboardHtml(metrics.snapshot());

from demystify_platform_observability import (
    create_metrics, mount_metrics_fastapi, render_dashboard_html, span_exporter_to_metrics,
)

metrics = create_metrics()
metrics.http_request("GET", "/v1/chat", 200, tenant_id, 12.4)
metrics.provider_call("openai", "gpt-4o", "ok", 210, 1500)
metrics.queue_depth("gateway", 7)

mount_metrics_fastapi(app, metrics)                 # GET /metrics
set_span_exporter(span_exporter_to_metrics(metrics))
html = render_dashboard_html(metrics.snapshot())

Mounting /metrics

• Hono: mountMetricsHono(app, metrics, "/metrics").
• FastAPI: mount_metrics_fastapi(app, metrics, "/metrics").
• Anything else: metricsHandler(metrics) / metrics_handler(metrics) returns {status, contentType, body} — wire it to your framework.

Span → metrics bridge

spanExporterToMetrics(metrics) returns an object matching the Wave-7 SpanExporter shape (export(span) in TS; a Callable[[Span], None] in Py). Pass it to a module's setSpanExporter(...) / set_span_exporter(...) and every finished span becomes an observation on dmstfy_span_duration_seconds. Off by default (no exporter registered = zero cost), exactly like §14.3.

Architecture & ports/adapters

| seam | implementation | notes | |---|---|---| | metric store | private prom-client / prometheus-client registry per Metrics | isolated; no global default registry | | snapshot | deterministic in-memory tally | ordering-stable; powers dashboard + parity | | exposition | metricsText() / metrics_text() | Prometheus v0.0.4 text |

Testing

make -C packages/platform-observability setup lint test build. Unit tests only (offline). Parity: TS and Py replay the same fixtures/snapshot.json and must produce byte-identical snapshots; metric names locked to fixtures/metric-names.json.

v1 scope

RED + cost + queue-depth + span-duration. No exemplars, no push-gateway, no histogram-quantile helpers (scrape + PromQL do that). Real Prometheus scrape is the standard opt-in path; nothing here requires it to run.