OTLP Adapter

The OTLP (OpenTelemetry Protocol) adapter sends logs in the standard OpenTelemetry format. This works with any OTLP-compatible backend including:

• Grafana Cloud (Loki)
• Datadog
• Honeycomb
• Jaeger
• Splunk
• New Relic
• Self-hosted OpenTelemetry Collector

Installation

The OTLP adapter comes bundled with evlog:

import { createOTLPDrain } from 'evlog/otlp'

Quick Start

1. Set your OTLP endpoint

OTLP_ENDPOINT=http://localhost:4318

2. Wire the drain to your framework

// server/plugins/evlog-drain.ts
import { createOTLPDrain } from 'evlog/otlp'

export default defineNitroPlugin((nitroApp) => {
  nitroApp.hooks.hook('evlog:drain', createOTLPDrain())
})

import { createOTLPDrain } from 'evlog/otlp'

app.use(evlog({ drain: createOTLPDrain() }))

import { createOTLPDrain } from 'evlog/otlp'

app.use(evlog({ drain: createOTLPDrain() }))

import { createOTLPDrain } from 'evlog/otlp'

await app.register(evlog, { drain: createOTLPDrain() })

import { createOTLPDrain } from 'evlog/otlp'

app.use(evlog({ drain: createOTLPDrain() }))

import { createOTLPDrain } from 'evlog/otlp'

EvlogModule.forRoot({ drain: createOTLPDrain() })

import { createOTLPDrain } from 'evlog/otlp'

initLogger({ drain: createOTLPDrain() })

Configuration

The adapter reads configuration from multiple sources (highest priority first):

1. Overrides passed to createOTLPDrain()
2. Runtime config at runtimeConfig.otlp (Nuxt/Nitro only)
3. Environment variables

Environment Variables

Standard OpenTelemetry variables are also supported as fallbacks:

Runtime Config (Nuxt only)

export default defineNuxtConfig({
  runtimeConfig: {
    otlp: {
      endpoint: '', // Set via NUXT_OTLP_ENDPOINT
    },
  },
})

Override Options

const drain = createOTLPDrain({
  endpoint: 'http://localhost:4318',
  serviceName: 'my-api',
  headers: {
    'Authorization': 'Bearer xxx',
  },
  resourceAttributes: {
    'deployment.environment': 'staging',
  },
})

Full Configuration Reference

Provider-Specific Setup

Grafana Cloud

1. Go to your Grafana Cloud portal
2. Navigate to Connections > Collector > OpenTelemetry
3. Copy your OTLP endpoint and generate credentials

OTLP_ENDPOINT=https://otlp-gateway-prod-us-central-0.grafana.net/otlp
OTEL_EXPORTER_OTLP_HEADERS=Authorization=Basic%20base64-encoded-credentials

Datadog

OTLP_ENDPOINT=https://http-intake.logs.datadoghq.com
OTLP_HEADERS=DD-API-KEY=your-api-key

Local OpenTelemetry Collector

For development and testing, run a local collector:

receivers:
  otlp:
    protocols:
      http:
        endpoint: 0.0.0.0:4318

exporters:
  debug:
    verbosity: detailed

service:
  pipelines:
    logs:
      receivers: [otlp]
      exporters: [debug]

docker run --rm -p 4318:4318 \
  -v $(pwd)/otel-collector.yaml:/etc/otelcol/config.yaml \
  otel/opentelemetry-collector:latest

OTLP_ENDPOINT=http://localhost:4318

OTLP Log Format

evlog maps wide events to the OTLP log format:

Severity Mapping

Troubleshooting

Missing endpoint error

[evlog/otlp] Missing endpoint. Set OTLP_ENDPOINT or OTEL_EXPORTER_OTLP_ENDPOINT

Make sure your endpoint environment variable is set and the server was restarted.

401 Unauthorized

Your authentication headers may be missing or incorrect. Check:

1. The OTEL_EXPORTER_OTLP_HEADERS format is correct
2. Credentials are valid and not expired
3. The endpoint URL is correct

404 Not Found

The adapter sends to /v1/logs. Make sure your endpoint:

• Supports OTLP HTTP (not gRPC)
• Is the base URL without /v1/logs suffix

Logs not appearing

1. Check the server console for [evlog/otlp] error messages
2. Test with a local collector first to verify the format
3. Check your backend's ingestion delay (some have 1-2 minute delays)

Direct API Usage

For advanced use cases:

import { sendToOTLP, sendBatchToOTLP, toOTLPLogRecord } from 'evlog/otlp'

// Send a single event
await sendToOTLP(event, {
  endpoint: 'http://localhost:4318',
})

// Send multiple events
await sendBatchToOTLP(events, {
  endpoint: 'http://localhost:4318',
})

// Convert event to OTLP format (for inspection)
const otlpRecord = toOTLPLogRecord(event)

Next Steps

• Axiom Adapter - Send logs to Axiom
• PostHog Adapter - Send logs to PostHog
• Custom Adapters - Build your own adapter
• Best Practices - Security and production tips