@nifty-lil-tricks/monitoring
Note: This is an experimental package under active development. New releases
may include breaking changes.
A selection of useful utilities (or nifty li'l tricks!) for all things
monitoring and OpenTelemetry.
Table of contents
Installation
Note: this package works with TypeScript v5 or later
npm install @nifty-lil-tricks/monitoring
Experimental stage 2 decorators
If you are using experimental stage 2 decorators, you will need to set the
following in your tsconfig.json
:
{
"compilerOptions": {
"experimentalDecorators": true,
"emitDecoratorMetadata": true
}
}
Stage 3 decorators
No setup is required.
Features
The following features are supported
Monitoring Decorator
Monitoring Decorator Overview
This decorator wraps all methods of a class in an
OpenTelemetry Span. If
a parent span cannot be retrieved from the context of the method call, it will
not be monitored.
The decorator will not affect any of the underlying functionality and it will
also handle any legitimate errors thrown from the underlying method as
appropriate.
Exported span for method that passes
A method of name hello
on class Service
that returns without error will
export the following span details by default:
{
"id": "b98126c289c5c9dc",
"name": "Service.hello",
"traceId": "a7b41739082880c506d62152de2e13a1",
"parentId": "f64d1571cd4a88dd",
"kind": 0,
"attributes": {
"monitoring.method": "hello",
"monitoring.class": "Service"
},
"status": { "code": 1 },
"timestamp": 1684136794317000,
"duration": 2010408,
"events": [],
"links": []
}
Exported span for method that throws
A method of name hello
on class Service
that throws an error will export the
following span details by default:
{
"id": "7c5f84a384af9a63",
"name": "Service.hello",
"traceId": "931ba33b4ab375ade4f26c7ac93df4ce",
"parentId": "0182507d0f5f0a85",
"kind": 0,
"attributes": {
"monitoring.method": "hello",
"monitoring.class": "Service"
},
"status": { "code": 2, "message": "Error: something bad happened" },
"timestamp": 1684136986170000,
"duration": 502605,
"events": [],
"links": []
}
Pre-requisites
Ensure
OpenTelemetry tracing is set-up
by ensuring:
- The provider is registered
- The monitored method is wrapped in the context of a parent span
- A global context manager is set up
See example set up for a quick guide to getting the above
setup.
Wrap all methods of a class in a span
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor()
class Service {
async hello(): Promise<void> {
await promisify(setTimeout)(500);
await this.nested();
}
async nested(): Promise<void> {
await promisify(setTimeout)(1000);
}
}
Filter allowed methods to monitor
By default, the monitor decorator monitors all
non-private
methods. One can provide an allowedMethods
option to filter the methods that
are monitored. This filter can be provided in several types:
string[]
RegExp
(methodName: string) => boolean
Filtering monitored methods by list of strings
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ allowedMethods: ["allowed1", "allowed2"] })
class Service {
notAllowed(): void {}
allowed1(): void {}
allowed2(): void {}
}
Filtering monitored methods by regex
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ allowedMethods: /^allowed.+/ })
class Service {
notAllowed(): void {}
allowed1(): void {}
allowed2(): void {}
}
Filtering monitored methods by function
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ allowedMethods: (method) => method.startsWith("allowed") })
class Service {
notAllowed(): void {}
allowed1(): void {}
allowed2(): void {}
}
Override the default Span kind
By default, the monitor decorator sets the Span Kind to be INTERNAL
. This
option allows one to override this.
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ spanKind: SpanKind.SERVER })
class Service {
async hello(): Promise<void> {
await promisify(setTimeout)(500);
}
}
Override the inferred class name
By default, the monitor decorator infers the class name from the class. This
option allows one to override this behaviour. A use-case for this would be when
one has multiple classes of the same name defined.
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ className: "OtherService" })
class Service {
async hello(): Promise<void> {
await promisify(setTimeout)(500);
}
}
Override the default tracer name
By default, the monitor decorator uses the default tracer to record spans. This
option allows one to override this behaviour.
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ tracerName: "some-other-tracer" })
class Service {
async hello(): Promise<void> {
await promisify(setTimeout)(500);
}
}
Caveats
Private methods
as defined here
are not monitoring by this decorator.
import { Monitor } from "@nifty-lil-tricks/monitoring";
import { promisify } from "node:util";
@Monitor({ tracerName: "some-other-tracer" })
class Service {
async hello(): Promise<void> {
await this.#privateMethod(())
}
async #privateMethod(): Promise<void> {
await promisify(setTimeout)(500);
}
}
API
The API docs can be found
here
Examples
Examples can be found
here.
Basic example
To run the examples/basic.ts
example, run the following:
- Ensure Docker is running
- Start the Jaeger collector:
npm run start:collector
- Run the example:
npm run example:basic
- Navigate to the Jaeger UI: http://localhost:16686
Nestjs example
To run the examples/basic.ts
example, run the following:
- Ensure Docker is running
- Start the Jaeger collector:
npm run start:collector
- Run the example:
npm run example:nestjs
- Make a request to the app:
curl http://localhost:3000/
- Navigate to the Jaeger UI: http://localhost:16686
Support
Platform Version | Supported | Notes |
---|
Node.JS v18 | :white_check_mark: | TypeScript v5+ for typings |
Node.JS v20 | :white_check_mark: | TypeScript v5+ for typings |
Deno v1 | :x: | Will be supported when OpenTelemetry is supported in Deno |
Web Browsers | :x: | Coming soon |
Useful links
License
Nifty li'l tricks packages are 100% free and open-source, under the
MIT license.
This package is Treeware. If you use it in production,
then we ask that you
buy the world a tree
to thank us for our work. By contributing to the Treeware forest you’ll be
creating employment for local families and restoring wildlife habitats.
Contributions
Contributions,
issues and feature requests are very welcome. If you are using this package and
fixed a bug for yourself, please consider submitting a PR!