Package that allows an OpenTelemetry baggage to be mutable.
npm install @uphold/opentelemetry-mutable-baggagePackage that allows an OpenTelemetry baggage to be mutable.
``sh`
npm install @uphold/opentelemetry-mutable-baggage
The default OpenTelemetry Baggage is immutable. Any change to it will create a new instance that you will need to save on the context. Because context is also immutable, saving the new baggage on the context will also create a new context. This makes it unsuitable for use-cases in which a piece of code needs to have visibility of items set on the baggage made by other pieces of code.
One common use-case is in frameworks with stack based middleware, such as Koa:
`js
// 1st middleware:
const requestLifecycleMiddleware = (context, next) => {
const { request } = context;
const createdAt = new Date();
const startedAt = process.hrtime();
try {
await next();
} finally {
// This will always be undefined!
const userId = api.propagation.getActiveBaggage()?.getEntry('user-id');
log.info({ userId }, Request to ${request.method} ${request.path});
}
};
// 2nd middleware:
const authenticationMiddleware = (context, next) => {
const baggage = api.propagation.getActiveBaggage();
const newBaggage = baggage?.setEntry('user-id', { value: 'faaebf49-c915-43ae-84fc-96c1711d2394' });
await api.context.with(api.context.setBaggage(baggage), next);
};
`
In the example above, requestLifecycleMiddleware will never see the user-id entry on the active baggage.
Replace W3CBaggagePropagator with W3CMutableBaggagePropagator, since it's a drop-in replacement. Here's how it looks if you are using the NodeSDK:
`js
import { CompositePropagator, W3CTraceContextPropagator } from '@opentelemetry/core';
import { W3CMutableBaggagePropagator } from '@uphold/opentelemetry-mutable-baggage';
const textMapPropagator = new CompositePropagator({
propagators: [new W3CTraceContextPropagator(), new W3CMutableBaggagePropagator()]
});
const sdk = new NodeSDK({
// ...
textMapPropagator
});
`
> ⚠️ The textMapPropagator option of the SDK will be ignored if both spanProcessor or traceExporter are not defined in the options. Either define those or call api.propagation.setGlobalPropagator(textMapPropagator) manually.
Then, use the regular propagation api to interact with the baggage:
`js
import { propagation } from '@opentelemetry/api';
// setEntry will no longer create a new baggage!`
propagation.getActiveBaggage()?.setEntry('foo', 'bar');
`sh``
npm test
Licensed under MIT.