a4e667de10
Single-commit clean baseline after security scrub of niche-tells, project codenames, internal jargon, and contributor-email leaks. Contents: - 100 Rust crates (_primitives/_rust/) - 37 agent manifests (_manifests/) + generated specs (_generated/) - 67 user-invocable skills (skills/) - 33 hooks (hooks/) - Composition blocks (_blocks/) - Documentation (docs/, README.md) - TS adapter packages (_ts_packages/) - Assembler (_assembler/) - Roles (_roles/) - Templates (_templates/) - Forgejo CI (.forgejo/) Author: Denis Parfionovich <info@greendragon.info> License: see LICENSE.
48 lines
3.5 KiB
Markdown
48 lines
3.5 KiB
Markdown
# OBSERVABILITY — Distributed traces (OpenTelemetry + W3C traceparent)
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A trace is a tree of spans across services, stitched by **trace_id**. Without traces, a p99-latency investigation in a microservice topology is a guessing game. OpenTelemetry is the vendor-neutral standard; pick a backend later.
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**Core data model (OTel spec 1.37+):**
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| Field | Meaning |
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|---|---|
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| `trace_id` | 16-byte hex (32 chars) — identifies the whole trace |
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| `span_id` | 8-byte hex (16 chars) — identifies one operation inside the trace |
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| `parent_span_id` | span_id of the caller (empty for root) |
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| `name` | Short operation name (`GET /users/:id`, `db.query`) |
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| `kind` | `server` / `client` / `producer` / `consumer` / `internal` |
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| `attributes` | Key-value metadata (`http.method`, `db.system`, `net.peer.name`) |
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| `status` | `OK` / `ERROR` + optional message |
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| `events` | Timestamped points inside the span (exceptions, annotations) |
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| `start_time` / `end_time` | nanosecond epoch |
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**W3C Trace Context propagation (mandatory for cross-service traces):**
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- Header: `traceparent: 00-<trace_id>-<span_id>-<flags>` [VERIFIED: www.w3.org/TR/trace-context/]
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- Example: `traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01`
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- Optional `tracestate: <vendor>=<value>,...` for vendor-specific data
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- Every service MUST propagate both headers unchanged on outbound requests; extract on inbound to continue the trace.
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**Sampling strategies (traces are expensive at volume):**
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- **Head-based** (decide at root): `ParentBased(TraceIdRatioBased(p))` with p=0.01-0.10 typical.
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- **Tail-based** (decide after span completes): OTel Collector `tail_sampling` processor — keep ALL errors + slow traces + sample p=0.01 rest [VERIFIED: github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/tailsamplingprocessor].
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- Hybrid preferred: head-sample 100% in dev, tail-sample in prod.
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**Transport (OTLP — the OTel wire protocol):**
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- OTLP/gRPC on port 4317 (default for app → collector, binary, efficient)
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- OTLP/HTTP on port 4318 (JSON / protobuf over HTTP, browser-friendly, firewall-friendly) [VERIFIED: opentelemetry.io/docs/specs/otlp/]
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- Collector is the choke point: apps ship OTLP → collector → backend (Jaeger, Tempo, Honeycomb, Datadog, Grafana Cloud).
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**Backends (pick by retention budget & query needs):**
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- **Jaeger** — self-host, in-memory or Cassandra/Elasticsearch storage [VERIFIED: jaegertracing.io]
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- **Tempo** (Grafana) — self-host, object-storage backend, cheapest at scale, trace-id-only lookup [VERIFIED: grafana.com/docs/tempo/]
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- **Vendor** — Honeycomb / Datadog / Lightstep / Grafana Cloud (pay per GB, no ops)
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**Language bindings:**
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- Rust: `opentelemetry` + `opentelemetry-otlp` + `tracing-opentelemetry` [VERIFIED: docs.rs/opentelemetry]
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- Go: `go.opentelemetry.io/otel` + auto-instrumentation for `net/http`, `database/sql` [VERIFIED: opentelemetry.io/docs/languages/go/]
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- Python: `opentelemetry-sdk` + `opentelemetry-instrumentation-<lib>` auto-loaders
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- Node/TS: `@opentelemetry/sdk-node` + `@opentelemetry/auto-instrumentations-node`
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**Log correlation:** every log entry MUST include `trace_id` + `span_id` fields (see `obs-structured-logs`). One click in Grafana / Tempo from trace → logs.
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**Forbidden:** rolling your own header format instead of W3C `traceparent` (breaks every off-the-shelf collector); sampling 100% in prod on >1k RPS service (cost + backend OOM); omitting `kind` on spans (breaks service-graph view); propagating `tracestate` across trust boundaries without validation (can be used for tracking).
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