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    @opentelemetry/instrumentation-express
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    0.28.0 • Public • Published

    OpenTelemetry Express Instrumentation for Node.js

    NPM Published Version dependencies devDependencies Apache License

    This module provides automatic instrumentation for express.

    For automatic instrumentation see the @opentelemetry/sdk-trace-node package.

    Compatible with OpenTelemetry JS API and SDK 1.0+.

    Installation

    This instrumentation relies on HTTP calls to also be instrumented. Make sure you install and enable both, otherwise you will not see any spans being exported from the instrumentation.

    npm install --save @opentelemetry/instrumentation-http @opentelemetry/instrumentation-express

    Supported Versions

    • ^4.0.0

    Usage

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

    To load the instrumentation, specify it in the Node Tracer's configuration:

    const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
    const { registerInstrumentations } = require('@opentelemetry/instrumentation');
    const { HttpInstrumentation } = require('@opentelemetry/instrumentation-http');
    const { ExpressInstrumentation } = require('@opentelemetry/instrumentation-express');
    
    const provider = new NodeTracerProvider();
    provider.register();
    
    registerInstrumentations({
      instrumentations: [
        // Express instrumentation expects HTTP layer to be instrumented
        new HttpInstrumentation(),
        new ExpressInstrumentation(),
      ],
    });

    See examples/express for a short example.

    Caveats

    Because of the way express works, it's hard to correctly compute the time taken by asynchronous middlewares and request handlers. For this reason, the time you'll see reported for asynchronous middlewares and request handlers still only represent the synchronous execution time, and not any asynchronous work.

    Express Instrumentation Options

    Express instrumentation has few options available to choose from. You can set the following:

    Options Type Example Description
    ignoreLayers IgnoreMatcher[] [/^\/_internal\//] Ignore layers that by match.
    ignoreLayersType ExpressLayerType[] ['request_handler'] Ignore layers of specified type.
    spanNameHook SpanNameHook () => 'my-span-name' Can be used to customize span names by returning a new name from the hook.

    ignoreLayers accepts an array of elements of types:

    • string for full match of the path,
    • RegExp for partial match of the path,
    • function in the form of (path) => boolean for custom logic.

    ignoreLayersType accepts an array of following strings:

    • router is the name of express.Router(),
    • middleware,
    • request_handler is the name for anything that's not a router or a middleware.

    spanNameHook is invoked with 2 arguments:

    • info: ExpressRequestInfo containing the incoming Express.js request, the current route handler creating a span and ExpressLayerType - the type of the handling layer or undefined when renaming the root HTTP instrumentation span.
    • defaultName: string - original name proposed by the instrumentation.

    Useful links

    License

    Apache 2.0 - See LICENSE for more information.

    Install

    npm i @opentelemetry/instrumentation-express

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    Version

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