What is @opentelemetry/instrumentation-express?
@opentelemetry/instrumentation-express is a package that provides automatic instrumentation for Express.js applications. It allows developers to collect and export telemetry data such as traces and metrics, which can be used for monitoring and performance analysis.
What are @opentelemetry/instrumentation-express's main functionalities?
Automatic Tracing
This code sets up automatic tracing for an Express.js application. It initializes a tracer provider, adds a span processor to export spans to the console, and registers the Express instrumentation.
const { NodeTracerProvider } = require('@opentelemetry/node');
const { SimpleSpanProcessor } = require('@opentelemetry/tracing');
const { ConsoleSpanExporter } = require('@opentelemetry/tracing');
const { ExpressInstrumentation } = require('@opentelemetry/instrumentation-express');
const provider = new NodeTracerProvider();
provider.addSpanProcessor(new SimpleSpanProcessor(new ConsoleSpanExporter()));
provider.register();
const expressInstrumentation = new ExpressInstrumentation();
expressInstrumentation.setTracerProvider(provider);
Custom Span Attributes
This code demonstrates how to add custom attributes to spans in an Express.js application. It retrieves the current active span and sets a custom attribute.
const express = require('express');
const { context, trace } = require('@opentelemetry/api');
const app = express();
app.use((req, res, next) => {
const span = trace.getSpan(context.active());
if (span) {
span.setAttribute('custom-attribute', 'custom-value');
}
next();
});
Error Handling
This code shows how to record exceptions in spans for error handling in an Express.js application. It captures the current active span and records the exception.
const express = require('express');
const { context, trace } = require('@opentelemetry/api');
const app = express();
app.use((err, req, res, next) => {
const span = trace.getSpan(context.active());
if (span) {
span.recordException(err);
}
res.status(500).send('Internal Server Error');
});
Other packages similar to @opentelemetry/instrumentation-express
express-opentracing
express-opentracing is a middleware for Express.js that provides OpenTracing instrumentation. It allows you to trace HTTP requests and responses in your Express application. Compared to @opentelemetry/instrumentation-express, it uses the OpenTracing API instead of OpenTelemetry.
zipkin-instrumentation-express
zipkin-instrumentation-express is a package that provides Zipkin instrumentation for Express.js applications. It allows you to collect and report trace data to a Zipkin server. Unlike @opentelemetry/instrumentation-express, it is specifically designed for use with Zipkin.
elastic-apm-node
elastic-apm-node is an Elastic APM agent for Node.js that provides instrumentation for various frameworks, including Express.js. It collects performance metrics and error data, which can be sent to an Elastic APM server. This package offers more comprehensive APM features compared to @opentelemetry/instrumentation-express.
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/instrumentation-express
Supported Versions
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 instrumentation (express in this case), specify it in the Node Tracer's configuration.
const { NodeTracerProvider } = require('@opentelemetry/node');
const { ExpressInstrumentation } = require('@opentelemetry/instrumentation-express');
const provider = new NodeTracerProvider();
provider.register();
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 will 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 | Description |
---|
ignoreLayers | IgnoreMatcher[] | Express instrumentation will not trace all layers that match. |
ignoreLayersType | ExpressLayerType[] | Express instrumentation 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
License
Apache 2.0 - See LICENSE for more information.