test: creating example code for Koa plugin

examples/koa/README.md

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+# Overview
+
+OpenTelemetry Koa Instrumentation allows the user to automatically collect trace data and export them to the backend of choice (we can use Zipkin or Jaeger for this example), to give observability to distributed systems.
+
+This is a simple example that demonstrates tracing calls made in a Koa application. The example
+shows key aspects of tracing such as
+- Root Span (on Client)
+- Child Span (on Client)
+- Span Events
+- Span Attributes
+
+## Installation
+
+```sh
+$ # from this directory
+$ npm install
+```
+
+Setup [Zipkin Tracing](https://zipkin.io/pages/quickstart.html)
+or
+Setup [Jaeger Tracing](https://www.jaegertracing.io/docs/latest/getting-started/#all-in-one)
+
+## Run the Application
+
+### Zipkin
+
+ - Run the server
+
+   ```sh
+   # from this directory
+   $ npm run zipkin:server
+   ```
+
+ - Run the client
+
+   ```sh
+   # from this directory
+   npm run zipkin:client
+   ```
+
+#### Zipkin UI
+`zipkin:server` script should output the `traceid` in the terminal (e.g `traceid: 4815c3d576d930189725f1f1d1bdfcc6`).
+Go to Zipkin with your browser [http://localhost:9411/zipkin/traces/(your-trace-id)]() (e.g http://localhost:9411/zipkin/traces/4815c3d576d930189725f1f1d1bdfcc6)
+
+<p align="center"><img src="./images/zipkin.jpg?raw=true"/></p>
+
+### Jaeger
+
+ - Run the server
+
+   ```sh
+   # from this directory
+   $ npm run jaeger:server
+   ```
+
+ - Run the client
+
+   ```sh
+   # from this directory
+   npm run jaeger:client
+   ```
+
+#### Jaeger UI
+
+`jaeger:server` script should output the `traceid` in the terminal (e.g `traceid: 4815c3d576d930189725f1f1d1bdfcc6`).
+Go to Jaeger with your browser [http://localhost:16686/trace/(your-trace-id)]() (e.g http://localhost:16686/trace/4815c3d576d930189725f1f1d1bdfcc6)
+
+<p align="center"><img src="images/jaeger.jpg?raw=true"/></p>
+
+## Useful links
+- For more information on OpenTelemetry, visit: <https://opentelemetry.io/>
+- For more information on OpenTelemetry for Node.js, visit: <https://github.com/open-telemetry/opentelemetry-js/tree/master/packages/opentelemetry-node>
+
+## LICENSE
+
+Apache License 2.0

examples/koa/client.js

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+'use strict';
+
+// eslint-disable-next-line import/order
+const tracer = require('./tracer')('example-koa-client');
+const api = require('@opentelemetry/api');
+const axios = require('axios').default;
+
+function makeRequest() {
+  const span = tracer.startSpan('client.makeRequest()', {
+    parent: tracer.getCurrentSpan(),
+    kind: api.SpanKind.CLIENT,
+  });
+
+  tracer.withSpan(span, async () => {
+    try {
+      const res = await axios.get('http://localhost:8081/run_test');
+      span.setStatus({ code: api.CanonicalCode.OK });
+      console.log(res.statusText);
+    } catch (e) {
+      span.setStatus({ code: api.CanonicalCode.UNKNOWN, message: e.message });
+    }
+    span.end();
+    console.log('Sleeping 5 seconds before shutdown to ensure all records are flushed.');
+    setTimeout(() => { console.log('Completed.'); }, 5000);
+  });
+}
+
+makeRequest();

examples/koa/package.json

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+{
+  "name": "koa-example",
+  "private": true,
+  "version": "0.8.0",
+  "description": "Example of Koa and @koa/router integration with OpenTelemetry",
+  "main": "index.js",
+  "scripts": {
+    "zipkin:server": "cross-env EXPORTER=zipkin node ./server.js",
+    "zipkin:client": "cross-env EXPORTER=zipkin node ./client.js",
+    "jaeger:server": "cross-env EXPORTER=jaeger node ./server.js",
+    "jaeger:client": "cross-env EXPORTER=jaeger node ./client.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+ssh://git@github.com/open-telemetry/opentelemetry-js-contrib.git"
+  },
+  "keywords": [
+    "opentelemetry",
+    "express",
+    "tracing"
+  ],
+  "engines": {
+    "node": ">=8"
+  },
+  "author": "OpenTelemetry Authors",
+  "license": "Apache-2.0",
+  "bugs": {
+    "url": "https://github.com/open-telemetry/opentelemetry-js-contrib/issues"
+  },
+  "dependencies": {
+    "@koa/router": "^9.3.1",
+    "@opentelemetry/api": "^0.8.3",
+    "@opentelemetry/exporter-jaeger": "^0.8.3",
+    "@opentelemetry/exporter-zipkin": "^0.8.3",
+    "@opentelemetry/node": "^0.8.3",
+    "@opentelemetry/plugin-http": "^0.8.3",
+    "@opentelemetry/plugin-koa": "../../plugins/node/opentelemetry-plugin-koa",
+    "@opentelemetry/tracing": "^0.8.3",
+    "axios": "^0.19.0",
+    "koa": "^2.13.0"
+  },
+  "homepage": "https://github.com/open-telemetry/opentelemetry-js-contrib#readme",
+  "devDependencies": {
+    "cross-env": "^6.0.0"
+  }
+}

examples/koa/server.js

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+'use strict';
+
+// eslint-disable-next-line
+const tracer = require('./tracer')('example-koa-server');
+
+
+// Adding Koa router (if desired)
+const router = require('@koa/router')();
+const koa = require('koa');
+
+// Setup koa
+const app = new koa();
+const PORT = 8081;
+
+// route definitions
+router.get('/run_test', runTest)
+    .get('/list', listPosts)
+    .get('/post/new', addPost)
+    .get('/post/:id', showPost);
+
+
+async function setUp () {
+    app.use(welcome);
+    app.use(router.routes());
+}
+
+/**
+ *  Router functions: list, add, or show posts
+*/
+const posts = ["post 0", "post 1", "post 2"];
+
+async function listPosts(ctx) {
+    ctx.body = "All posts: " + posts;
+    console.log("listPosts");
+    const addNewPost = ctx.redirect(`/post/new`);
+}
+
+async function addPost(ctx) {
+    posts.push("post " + posts.length);
+    console.log("addPost");
+    const currentSpan = tracer.getCurrentSpan();
+    currentSpan.addEvent("Added post");
+    currentSpan.setAttribute("Date", new Date);
+    ctx.body = "Added post: " + posts[posts.length-1];
+    const viewNewPost = ctx.redirect(`/post/3`);
+}
+
+async function showPost(ctx) {
+    console.log("showPost");
+    const id = ctx.params.id;
+    const post = posts[id];
+    if (!post) ctx.throw(404, 'Invalid post id');
+    ctx.body = post;
+}
+
+async function runTest (ctx, next) {
+    console.log("runTest");
+    const postList = await ctx.redirect(`/list`);
+
+}
+
+function welcome (ctx, next) {
+    ctx.body = "Welcome to the Koa example";
+    next();
+}
+
+setUp().then(() => {
+    app.listen(PORT);
+    console.log(`Listening on http://localhost:${PORT}`);
+  });

examples/koa/tracer.js

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+'use strict';
+
+const opentelemetry = require('@opentelemetry/api');
+const { NodeTracerProvider } = require('@opentelemetry/node');
+const { SimpleSpanProcessor } = require('@opentelemetry/tracing');
+const { JaegerExporter } = require('@opentelemetry/exporter-jaeger');
+const { ZipkinExporter } = require('@opentelemetry/exporter-zipkin');
+
+module.exports = (serviceName) => {
+  const provider = new NodeTracerProvider({
+    plugins: {
+      koa: {
+        enabled: true,
+        path: "@opentelemetry/plugin-koa",
+        enhancedDatabaseReporting: true
+      },
+      http: {
+        enabled: true,
+        path: '@opentelemetry/plugin-http',
+      },
+    },
+  });
+
+  provider.addSpanProcessor(new SimpleSpanProcessor(new ZipkinExporter({
+    serviceName,
+  })));
+  provider.addSpanProcessor(new SimpleSpanProcessor(new JaegerExporter({
+    serviceName,
+  })));
+
+  // Initialize the OpenTelemetry APIs to use the NodeTracerProvider bindings
+  provider.register();
+
+  return opentelemetry.trace.getTracer('koa-example');
+};