# OpenTelemetry environment variable reference for Belvador

> Export, identity, sampling, batching and off-switch variables, plus the runtime-specific ones Belvador's recipes use.

Every OpenTelemetry SDK reads the same standard variables. This page lists the ones that matter for Belvador, what to set them to, and the runtime-specific ones the recipes use. The [quickstart](https://belvador.dev/en/docs/otel/quickstart#2-set-the-standard-variables) shows the block with your project filled in.

## Export

| Variable | Value for Belvador | Notes |
|---|---|---|
| `OTEL_EXPORTER_OTLP_ENDPOINT` | `https://ingest.belvador.dev/otlp/<project-id>` | The exporter appends `/v1/traces` and `/v1/logs` |
| `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`, `OTEL_EXPORTER_OTLP_LOGS_ENDPOINT` | Full URL including `/v1/traces` or `/v1/logs` | Only if you send each signal somewhere different |
| `OTEL_EXPORTER_OTLP_PROTOCOL` | `http/protobuf` | `http/json` also works; `grpc` does not — use a [Collector](https://belvador.dev/en/docs/otel/collector) |
| `OTEL_EXPORTER_OTLP_HEADERS` | `Authorization=Bearer%20<ingest key>` | Comma-separated `key=value` pairs, values percent-encoded |
| `OTEL_EXPORTER_OTLP_COMPRESSION` | `gzip` (optional) | Quotas and the rate limit count bytes as received, so compression stretches both |
| `OTEL_EXPORTER_OTLP_TIMEOUT` | Default (10000 ms) | Raise only for slow networks |
| `OTEL_TRACES_EXPORTER` | `otlp` | `none` stops traces |
| `OTEL_LOGS_EXPORTER` | `otlp` | `none` stops logs |
| `OTEL_METRICS_EXPORTER` | `none`, or `otlp` to send [metrics](https://belvador.dev/en/docs/otel/metrics) | Needs a key with **Metrics**; set `OTEL_METRIC_EXPORT_INTERVAL=60000` with it |

## Identity

| Variable | Value | Notes |
|---|---|---|
| `OTEL_SERVICE_NAME` | Your service's name | Shown in Traces, Logs and the Connection tab |
| `OTEL_RESOURCE_ATTRIBUTES` | `deployment.environment.name=production` | Comma-separated; add `service.version=<release>` to tell deploys apart |

Records without an environment are stored with an empty one; a key restricted to some environments drops them.

## Sampling and propagation

| Variable | Value | Notes |
|---|---|---|
| `OTEL_TRACES_SAMPLER` | `parentbased_traceidratio` | Follows the caller's decision; see [Sampling and cost](https://belvador.dev/en/docs/otel/sampling-and-cost) |
| `OTEL_TRACES_SAMPLER_ARG` | `0.1` … `1` | Share of new traces kept |
| `OTEL_PROPAGATORS` | Default (`tracecontext,baggage`) | W3C Trace Context, the same headers the Belvador SDK sends |

## Batching

| Variable | Default | When to change |
|---|---|---|
| `OTEL_BSP_SCHEDULE_DELAY`, `OTEL_BLRP_SCHEDULE_DELAY` | 5000 ms (traces), 1000 ms (logs) | Lower for short-lived processes |
| `OTEL_BSP_MAX_EXPORT_BATCH_SIZE`, `OTEL_BLRP_MAX_EXPORT_BATCH_SIZE` | 512 | Lower if requests hit `413` (over 4 MiB) |
| `OTEL_BSP_MAX_QUEUE_SIZE`, `OTEL_BLRP_MAX_QUEUE_SIZE` | 2048 | Raise for bursts; records beyond the queue are dropped in your process |

## Turning it off

`OTEL_SDK_DISABLED=true` disables the SDK in runtimes that support it (Node.js, Python, Java, Go's env-based setup ignores it). Unsetting `OTEL_EXPORTER_OTLP_ENDPOINT` sends to `localhost:4318` instead, which usually fails quietly — prefer `OTEL_TRACES_EXPORTER=none` and `OTEL_LOGS_EXPORTER=none`.

## Runtime-specific variables in the recipes

| Variable | Runtime | Why the recipe sets it |
|---|---|---|
| `OTEL_SEMCONV_STABILITY_OPT_IN=http` | Node.js, Python | Stable HTTP attribute names (`url.path`, `http.request.method`, `http.response.status_code`) |
| `OTEL_NODE_RESOURCE_DETECTORS=env,host,os` | Node.js | Leaves out the `process` detector, which copies the command line into every span |
| `OTEL_NODE_DISABLED_INSTRUMENTATIONS` | Node.js | Comma-separated instrumentations to skip (`fs,dns,net`) |
| `OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED=true` | Python | Sends `logging` records |
| `OTEL_PYTHON_DISABLED_INSTRUMENTATIONS` | Python | Comma-separated instrumentations to skip |
| `OTEL_DENO=true` | Deno | Turns on the built-in exporter |
| `JAVA_TOOL_OPTIONS=-javaagent:…` | Java | Attaches the agent where you cannot change the start command |