zipkin

zipkin

This is the core npm package for Zipkin. It contains the public API which is used by the various plugins (instrumentations and transports).

We include TypeScript definition file which you can also use as documentation.

Developing

Please always make sure that TypeScript type definitions match source code modifications.

Usage

const zipkin = require('zipkin');

// In Node.js, the recommended context API to use is zipkin-context-cls.
const CLSContext = require('zipkin-context-cls');
const ctxImpl = new CLSContext(); // if you want to use CLS
const xtxImpl = new zipkin.ExplicitContext(); // Alternative; if you want to pass around the context manually

// Tracer will be a one to many relationship with instrumentation that use it (like express)
const tracer = new zipkin.Tracer({
  ctxImpl, // the in-process context
  recorder: new zipkin.ConsoleRecorder(), // For easy debugging. You probably want to use an actual implementation, like Kafka or AWS SQS.
  sampler: new zipkin.sampler.CountingSampler(0.01), // sample rate 0.01 will sample 1 % of all incoming requests
  traceId128Bit: true, // to generate 128-bit trace IDs. 64-bit (false) is default
  localServiceName: 'my-service' // indicates this node in your service graph
});

In-process context (node only)

The event loop is what allows Node.js to perform non-blocking I/O operations, hence several operations are happening at the same time and we need a way to correlate different operations that happen at the same time to a specific trace. There are two options for this: explicit and implicit context.

In the explicit context, we pass around an object ctx from the top layer of the application down to those operations we want to trace. For example, a ctx will be handed from the HTTP handler down to the application layer and finally to a HTTP call that queries external resources.

In the implicit context, we don't need to pass anything, the in-process context is transparent for the user (see zipkin-context-cls).

Local tracing

Sometimes you have activity that precedes a remote request that you want to capture in a trace. tracer.local can time an operation, placing a corresponding span ID in scope so that any downstream commands end up in the same trace.

Here's an example tracing a synchronous function:

// A span representing checkout completes before result is returned
const result = tracer.local('checkout', () => {
  return someComputation();
});

Here's an example tracing a function that returns a promise:

// A span is in progress and completes when the promise is resolved.
const result = tracer.local('checkout', () => {
  return createAPromise();
});