open-telemetry
OpenTelemetry Express Instrumentation for Node.js
This module provides automatic instrumentation for the express 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+.
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-expressSupported Versions
expressversion>=4.0.0 <6
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. |
requestHook |
ExpressRequestCustomAttributeFunction (function) |
(span, info) => {} |
Function for adding custom attributes on Express request. Receives params: Span, ExpressRequestInfo. |
ignoreLayers accepts an array of elements of types:
stringfor full match of the path,RegExpfor partial match of the path,functionin the form of(path) => booleanfor custom logic.
ignoreLayersType accepts an array of following strings:
routeris the name ofexpress.Router(),middleware,request_handleris the name for anything that's not a router or a middleware.
spanNameHook is invoked with 2 arguments:
info: ExpressRequestInfocontaining the incoming Express.js request, the current route handler creating a span andExpressLayerType- the type of the handling layer.defaultName: string- original name proposed by the instrumentation.
requestHook is invoked with 2 arguments:
span: Span- the span associated with the express request.info: ExpressRequestInfocontaining the incoming Express.js request, the current route handler creating a span andExpressLayerType- the type of the handling layer.
NOTE: ExpressRequestInfo.request is typed as any. If you want type support make sure you have @types/express installed then you can use ExpressRequestInfo<express.Request>
Ignore a whole Express route
In order to ignore whole traces that represent a given Express route, use
the ignoreIncomingRequestHook option from
@opentelemetry/instrumentation-http against the route path. Ideally, this
shouldn't be necessary since spans should a have low cardinality and minimize
interaction between instrumentation libraries but
@opentelemetry/instrumentation-express renames the root span from
@opentelemetry/instrumentation-http in order to get things in order.
registerInstrumentations({
instrumentations: [
// Express instrumentation expects HTTP layer to be instrumented
new HttpInstrumentation({
ignoreIncomingRequestHook(req) {
// Ignore spans from static assets.
const isStaticAsset = !!req.url.match(/^\/static\/.*$/);
return isStaticAsset;
}
}),
new ExpressInstrumentation(),
],
});Using requestHook
Instrumentation configuration accepts a custom "hook" function which will be called for every instrumented Express layer involved in a request. Custom attributes can be set on the span or run any custom logic per layer.
Here is a simple example that adds to the request handler span some attributes based on the Express request attributes:
import { ExpressInstrumentation, ExpressLayerType } from "@opentelemetry/instrumentation-express"
const expressInstrumentation = new ExpressInstrumentation({
requestHook: function (
span: Span,
info: ExpressRequestInfo,
) {
if (info.layerType === ExpressLayerType.REQUEST_HANDLER) {
span.setAttribute(
'http.method',
info.request.method
);
span.setAttribute(
'express.base_url',
info.request.baseUrl
);
}
}
});Semantic Conventions
This package uses @opentelemetry/semantic-conventions version 1.22+, which implements Semantic Convention Version 1.7.0
Attributes collected:
| Attribute | Short Description |
|---|---|
http.route |
The matched route (path template). |
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.