App.js

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
import { Tracer, ExplicitContext, BatchRecorder, jsonEncoder, Annotation } from 'zipkin';
import wrapFetch from 'zipkin-instrumentation-fetch';
import { HttpLogger } from 'zipkin-transport-http';

const { JSON_V2 } = jsonEncoder;

const zipkinBaseUrl = 'http://localhost:9411';
const tracer = new Tracer({
  ctxImpl: new ExplicitContext(),
  recorder: new BatchRecorder({
    logger: new HttpLogger({
      endpoint: `${zipkinBaseUrl}/api/v2/spans`,
      jsonEncoder: JSON_V2,
      fetch,
    }),
  }),
  localServiceName: 'react-native',
});

export default class App extends React.Component {
  state = {
    person: 'Not loaded',
    tracer,
    fetch: wrapFetch(fetch, {tracer, remoteServiceName: 'starwars'}), 
  };

  componentWillMount() {
    const randomNumber = Math.floor(Math.random() * 10) + 1;
    this.state.tracer.local('pay-me', () =>
      this.state.fetch("https://swapi.co/api/people/" + randomNumber)
        .then(response => response.json())
        .then(person => this.setState({
          person: person.name,
        })
        ).catch(e => console.error(e))
    );
  }

  render() {
    return (
      <View style={styles.container}>
        <Text>{this.state.person}</Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});