OtelBridge

warning

The OpenTelemetry Bridge is currently experimental. APIs and configuration options may change in future releases.

Enables bidirectional integration between Mastra tracing and OpenTelemetry infrastructure. Creates native OTEL spans for Mastra operations and inherits context from active OTEL spans. Also forwards Mastra log events to the globally-registered OTEL LoggerProvider, emitting each log under the OTEL context of the originating Mastra span so trace-log correlation works automatically.

Constructor

new OtelBridge(config?: OtelBridgeConfig)

Methods

executeInContext

executeInContext<T>(spanId: string, fn: () => Promise<T>): Promise<T>

Executes an async function within the OTEL context of a Mastra span. OTEL-instrumented code running inside the function will have correct parent relationships.

Returns: Promise<T> - The result of the function execution.

executeInContextSync

executeInContextSync<T>(spanId: string, fn: () => T): T

Executes a synchronous function within the OTEL context of a Mastra span.

Returns: T - The result of the function execution.

onLogEvent

async onLogEvent(event: LogEvent): Promise<void>

Forwards a Mastra log event to the globally-registered OTEL LoggerProvider. Trace correlation is resolved in this order:

1. If the log carries a spanId the bridge has an OTEL span for, the log is emitted under that span's stored OTEL context.
2. Otherwise, if the log carries traceId and spanId, those IDs are attached to the emitted log record's SpanContext.
3. Otherwise, the log is emitted under whatever OTEL context is currently active.

If no LoggerProvider is registered globally, emission is a silent no-op.

flush

async flush(): Promise<void>

Force flushes the global OTEL tracer provider and logger provider if they support forceFlush. Useful in serverless environments where you need to drain telemetry before the runtime terminates.

shutdown

async shutdown(): Promise<void>

Shuts down the bridge and cleans up resources. Ends any spans that weren't properly closed.

Usage examples

Basic Usage

import { Mastra } from '@mastra/core'
import { Observability } from '@mastra/observability'
import { OtelBridge } from '@mastra/otel-bridge'

const mastra = new Mastra({
  observability: new Observability({
    configs: {
      default: {
        serviceName: 'my-service',
        bridge: new OtelBridge(),
      },
    },
  }),
  agents: { myAgent },
})

Combined with Exporters

The bridge can be used alongside exporters. The bridge handles OTEL context, while exporters send data to additional destinations:

import { Mastra } from '@mastra/core'
import { Observability, MastraStorageExporter } from '@mastra/observability'
import { OtelBridge } from '@mastra/otel-bridge'
import { LangfuseExporter } from '@mastra/langfuse'

const mastra = new Mastra({
  observability: new Observability({
    configs: {
      default: {
        serviceName: 'my-service',
        bridge: new OtelBridge(), // Handles OTEL context
        exporters: [
          new MastraStorageExporter(), // Studio access
          new LangfuseExporter({
            // Additional destination
            publicKey: process.env.LANGFUSE_PUBLIC_KEY,
            secretKey: process.env.LANGFUSE_SECRET_KEY,
          }),
        ],
      },
    },
  }),
})

Setup requirements

The bridge creates spans through an OpenTelemetry tracer provider. For Mastra spans to be exported:

• A tracer provider must be available. Register one globally before Mastra runs, for example by calling sdk.start() on NodeSDK from @opentelemetry/sdk-node, or by calling trace.setGlobalTracerProvider(provider). If the provider isn't registered globally, pass it with new OtelBridge({ tracerProvider }).
• A context manager must be installed for Mastra spans to nest under outer spans. NodeSDK installs one automatically. Without a context manager, spans are still exported, but Mastra root spans can't read the active span, so they start new traces instead of joining the outer trace.

When no tracer provider is available, agents and workflows still run, but no Mastra spans are exported through OpenTelemetry. The bridge logs this warning once:

[OtelBridge] No OpenTelemetry tracer provider is registered globally, so Mastra spans will not be exported through OpenTelemetry. ...

See the OtelBridge Guide for complete setup instructions, including how to configure OTEL instrumentation and run your application.

Tags support

The OtelBridge supports trace tagging for categorization and filtering. Tags are only applied to root spans and are included as the mastra.tags attribute on native OTEL spans.

Usage

const result = await agent.generate('Hello', {
  tracingOptions: {
    tags: ['production', 'experiment-v2', 'user-request'],
  },
})

How Tags Are Stored

Tags are stored as a JSON-stringified array in the mastra.tags span attribute:

{
  "mastra.tags": "[\"production\",\"experiment-v2\",\"user-request\"]"
}

The format is compatible with all OTEL-compatible backends and collectors.

Related

• OtelBridge Guide: Setup guide with examples
• Tracing Overview: General tracing concepts
• OtelExporter Reference: OTEL exporter for sending traces