OpenTelemetry Express Instrumentation for Node.js

This module provides automatic instrumentation for express.

For automatic instrumentation see the @opentelemetry/node package.

Installation

npm install --save @opentelemetry/plugin-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 a specific plugin (express in this case), specify it in the registerInstrumentations's configuration.

const { NodeTracerProvider } = require('@opentelemetry/node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');

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

registerInstrumentations({
  instrumentations: [
    {
      plugins: {
        express: {
          enabled: true,
          // You may use a package name or absolute path to the file.
          path: '@opentelemetry/plugin-express',
        }
      }
    },
  ],
  tracerProvider: provider,
});

To load all the supported plugins, use below approach. Each plugin is only loaded when the module that it patches is loaded; in other words, there is no computational overhead for listing plugins for unused modules.

const { NodeTracerProvider } = require('@opentelemetry/node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');

const provider = new NodeTracerProvider();
provider.register();
registerInstrumentations({
  tracerProvider: provider,
});

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 will only represent the synchronous execution time, and not any asynchronous work.

Express Plugin Options

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

Options	Type	Description
ignoreLayers	IgnoreMatcher[]	Express plugin will not trace all layers that match.
ignoreLayersType	ExpressLayerType[]	Express plugin will ignore the layers that match based on their type.

For reference, here are the three different layer type:

• router is the name of express.Router()
• middleware
• request_handler is the name for anything thats not a router or a middleware.

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.