@opentelemetry/instrumentation-koa

OpenTelemetry Koa Instrumentation for Node.js

This module provides automatic instrumentation for the Koa module, which may be loaded using the @opentelemetry/sdk-trace-node package and is included in the @opentelemetry/auto-instrumentations-node bundle.

If total installation size is not constrained, it is recommended to use the @opentelemetry/auto-instrumentations-node bundle with @opentelemetry/sdk-node for the most seamless instrumentation experience.

Compatible with OpenTelemetry JS API and SDK 1.0+.

Status

Maturity	Component Owner	Compatibility
Unmaintained	N/A	API 1.0+ SDK 1.0+

Installation

npm install --save @opentelemetry/instrumentation-koa

Supported Versions

• koa versions >=2.0.0 <4
• @koa/router versions >=8.0.0

Usage

OpenTelemetry Koa Instrumentation allows the user to automatically collect trace data and export them to their backend of choice, to give observability to distributed systems.

const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');
const { KoaInstrumentation } = require('@opentelemetry/instrumentation-koa');

const provider = new NodeTracerProvider();
provider.register();

registerInstrumentations({
  instrumentations: [
    new KoaInstrumentation(),
  ],
});

See examples/koa for a short example using both Koa and @koa/router.

Note that generator-based middleware are deprecated and won't be instrumented.

Koa Instrumentation Options

Options	Type	Example	Description
ignoreLayersType	KoaLayerType[]	['middleware']	Ignore layers of specified type.
requestHook	KoaRequestCustomAttributeFunction	(span, info) => {}	Function for adding custom attributes to Koa middleware layers. Receives params: Span, KoaRequestInfo.

ignoreLayersType accepts an array of KoaLayerType which can take the following string values:

• router,
• middleware.

Using requestHook

Instrumentation configuration accepts a custom "hook" function which will be called for every instrumented Koa middleware layer involved in a request. Custom attributes can be set on the span or run any custom logic per layer.

NOTE: KoaRequestInfo.context and KoaRequestInfo.middlewareLayer are typed as any. If you want type support make sure you have @types/koa and @types/koa__router installed then you can use the following type definitions:

import { KoaInstrumentation } from "@opentelemetry/instrumentation-koa"
import type { Middleware, ParameterizedContext, DefaultState } from 'koa';
import type { RouterParamContext } from '@koa/router';

type KoaContext = ParameterizedContext<DefaultState, RouterParamContext>;
type KoaMiddleware = Middleware<DefaultState, KoaContext>;

const koaInstrumentation = new KoaInstrumentation({
  requestHook: function (span: Span, info: KoaRequestInfo<KoaContext, KoaMiddleware>) {
    span.setAttribute(
      'http.method',
      info.context.request.method
    )
  }
});

Koa Packages

This package provides automatic tracing for middleware added using either the core koa package or the @koa/router package.

Useful links

• For more information on OpenTelemetry, visit: https://opentelemetry.io/
• For more about OpenTelemetry JavaScript: https://github.com/open-telemetry/opentelemetry-js
• For help or feedback on this project, join us in GitHub Discussions

License

Apache 2.0 - See LICENSE for more information.

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