What is @opentelemetry/api?
The @opentelemetry/api package provides a set of APIs to instrument JavaScript applications for telemetry purposes. It allows developers to collect traces and metrics from their applications, which can then be exported to various observability backends for monitoring and analysis. The API is designed to be minimal, extensible, and vendor-neutral.
What are @opentelemetry/api's main functionalities?
Tracing
This feature allows the creation and management of traces to monitor the flow of a request through various services. The code sample demonstrates how to create a tracer, start a new span, and then end the span.
const { trace } = require('@opentelemetry/api');
const tracer = trace.getTracer('example-tracer');
const span = tracer.startSpan('example-span');
span.end();
Context Propagation
This feature enables the propagation of context information across asynchronous operations or service boundaries. The code sample shows how to associate a span with a context and execute a function within this context.
const { context, trace } = require('@opentelemetry/api');
const currentContext = context.active();
const span = trace.getTracer('example-tracer').startSpan('example-span');
context.with(trace.setSpan(currentContext, span), () => {
// Your synchronous or asynchronous operation here
span.end();
});
Metrics
This feature supports the collection of quantitative measurements of operational events, such as request counts. The code sample illustrates how to create a meter, define a counter metric, and increment the counter.
const { metrics } = require('@opentelemetry/api');
const meter = metrics.getMeter('example-meter');
const counter = meter.createCounter('example-counter');
counter.add(1);
Other packages similar to @opentelemetry/api
jaeger-client
Jaeger client is a package for tracing applications and sending the traces to Jaeger, a distributed tracing system. Unlike @opentelemetry/api, which is designed to be vendor-neutral and supports multiple backends, jaeger-client is specifically tailored for integration with Jaeger.
prom-client
Prom-client is a package for collecting metrics in Node.js applications and exporting them to Prometheus, a monitoring and alerting toolkit. While @opentelemetry/api provides a more general approach to metrics collection compatible with various backends, prom-client is specifically focused on Prometheus integration.
OpenTelemetry API for JavaScript
This package provides everything needed to interact with the OpenTelemetry API, including all TypeScript interfaces, enums, and no-op implementations. It is intended for use both on the server and in the browser.
Quick Start
To get started you need to install the SDK and plugins, create a TracerProvider and/or MeterProvider, and register it with the API.
Install Dependencies
$
$ npm install \
@opentelemetry/api \
@opentelemetry/core \
@opentelemetry/node \
@opentelemetry/tracing \
@opentelemetry/exporter-jaeger \
@opentelemetry/plugin-http
$
$ npm install \
@opentelemetry/metrics \
@opentelemetry/exporter-prometheus
Note: this example is for node.js. See examples/tracer-web for a browser example.
Initialize the SDK
Before any other module in your application is loaded, you must initialize the global tracer and meter providers. If you fail to initialize a provider, no-op implementations will be provided to any library which acquires them from the API.
To collect traces and metrics, you will have to tell the SDK where to export telemetry data to. This example uses Jaeger and Prometheus, but exporters exist for other tracing backends. If you're not sure if there is an exporter for your tracing backend, contact your tracing provider.
Tracing
const { NodeTracerProvider } = require("@opentelemetry/node");
const { SimpleSpanProcessor } = require("@opentelemetry/tracing");
const { JaegerExporter } = require("@opentelemetry/exporter-jaeger");
const tracerProvider = new NodeTracerProvider();
tracerProvider.addSpanProcessor(
new SimpleSpanProcessor(
new JaegerExporter({
serviceName: 'my-service'
})
)
);
tracerProvider.register();
Metrics
const api = require("@opentelemetry/api");
const { MeterProvider } = require("@opentelemetry/metrics");
const { PrometheusExporter } = require("@opentelemetry/exporter-prometheus");
const meterProvider = new MeterProvider({
exporter: new PrometheusExporter({ startServer: true }),
interval: 1000,
});
api.metrics.setGlobalMeterProvider(meterProvider);
Version Compatibility
Because the npm installer and node module resolution algorithm could potentially allow two or more copies of any given package to exist within the same node_modules
structure, the OpenTelemetry API takes advantage of a variable on the global
object to store the global API. When an API method in the API package is called, it checks if this global
API exists and proxies calls to it if and only if it is a compatible API version. This means if a package has a dependency on an OpenTelemetry API version which is not compatible with the API used by the end user, the package will receive a no-op implementation of the API.
Advanced Use
API Registration Options
If you prefer to choose your own propagator or context manager, you may pass an options object into the tracerProvider.register()
method. Omitted or undefined
options will be replaced by a default value and null
values will be skipped.
const { B3Propagator } = require("@opentelemetry/core");
tracerProvider.register({
propagator: new B3Propagator(),
contextManager: null,
});
API Methods
If you are writing an instrumentation library, or prefer to call the API methods directly rather than using the register
method on the Tracer/Meter Provider, OpenTelemetry provides direct access to the underlying API methods through the @opentelemetry/api
package. API entry points are defined as global singleton objects trace
, metrics
, propagation
, and context
which contain methods used to initialize SDK implementations and acquire resources from the API.
const api = require("@opentelemetry/api");
api.trace.setGlobalTracerProvider(tracerProvider);
api.trace.getTracerProvider();
api.trace.getTracer(name, version);
api.metrics.setGlobalMeterProvider(meterProvider);
api.metrics.getMeterProvider();
api.metrics.getMeter(name, version);
api.propagation.setGlobalPropagator(httpTraceContextPropagator);
api.context.setGlobalContextManager(asyncHooksContextManager);
Library Authors
Library authors need only to depend on the @opentelemetry/api
package and trust that the application owners which use their library will initialize an appropriate SDK.
const api = require("@opentelemetry/api");
const tracer = api.trace.getTracer("my-library-name", "0.2.3");
async function doSomething() {
const span = tracer.startSpan("doSomething", { parent: tracer.getCurrentSpan() });
try {
const result = await doSomethingElse();
span.end();
return result;
} catch (err) {
span.setStatus({
code: api.CanonicalCode.INTERNAL,
message: err.message,
});
span.end();
return null;
}
}
Useful links
License
Apache 2.0 - See LICENSE for more information.