paperclip/doc/observability.md

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# Observability
Paperclip ships with **opt-in** OpenTelemetry auto-instrumentation for the
server process. When activated it produces **traces only** — no metrics and no
logs are exported by this integration. The OTel packages are *optional peer
dependencies*: they are not in the default lockfile and are loaded dynamically
only when an operator turns the feature on.
When `OTEL_EXPORTER_OTLP_ENDPOINT` is unset, none of the `@opentelemetry/*`
packages are imported and there is zero runtime overhead.
## Enabling tracing
### 1. Install the OTel peer dependencies
Install the SDK, the auto-instrumentations bundle, the resources/semconv
helpers, and **one** exporter matching your chosen OTLP protocol.
Common to every protocol:
```bash
pnpm add \
@opentelemetry/sdk-node \
@opentelemetry/auto-instrumentations-node \
@opentelemetry/resources \
@opentelemetry/semantic-conventions
```
Then add the exporter for the protocol you intend to use:
| `OTEL_EXPORTER_OTLP_PROTOCOL` | Exporter package |
| ----------------------------- | --------------------------------------------- |
| `grpc` (default if unset) | `@opentelemetry/exporter-trace-otlp-grpc` |
| `http/protobuf` | `@opentelemetry/exporter-trace-otlp-proto` |
| `http/json` | `@opentelemetry/exporter-trace-otlp-http` |
For example, for the default gRPC path:
```bash
pnpm add @opentelemetry/exporter-trace-otlp-grpc
```
### 2. Set the environment
Minimal setup:
```bash
# Required — turns the feature on. Point at your collector.
# For grpc this is the gRPC target (typically port 4317). For the HTTP
# protocols give the collector's BASE URL (typically port 4318) — the
# exporter appends /v1/traces itself.
export OTEL_EXPORTER_OTLP_ENDPOINT="http://otel-collector:4317"
# Optional — protocol. Defaults to grpc when unset.
# Valid values: grpc | http/protobuf | http/json
export OTEL_EXPORTER_OTLP_PROTOCOL="grpc"
# Optional — service identity attached to every span.
export OTEL_SERVICE_NAME="paperclip"
export OTEL_SERVICE_VERSION="2026.5.0"
```
If `OTEL_EXPORTER_OTLP_PROTOCOL` is set to an unrecognized value, Paperclip
logs a single warning and falls back to gRPC.
If `OTEL_EXPORTER_OTLP_ENDPOINT` is set but the OTel packages are not
installed, the server logs a single diagnostic line on boot and continues
without tracing — your server stays up.
## Scope
This integration emits **traces only**. Metrics and log exporters are out of
scope and intentionally not configured here. Auto-instrumentations for
`fs`, `dns`, and `net` are disabled by default because they are too chatty
for this workload; everything else from
`@opentelemetry/auto-instrumentations-node` is on (HTTP, Express, PG, etc.).