updated node.js linux example to include a slow function

Author: dmitchsplunk

instrumentation/nodejs/linux/README.md

@@ -34,7 +34,7 @@ Open a command line terminal and navigate to the root of the directory.
 For example:
 
 ````
-cd ~/splunk-opentelemetry-examples/instrumentation/nodejs
+cd ~/splunk-opentelemetry-examples/instrumentation/nodejs/linux
 ````
 
 ### Initialize NPM and Install Packages (Optional)
@@ -53,18 +53,18 @@ npm install express
 npm install pino
 ````
 
-There's no need to run these commands again as you can use the `package.json` file that 
-was already created. 
-
-### Instrument with the Splunk Distribution of OpenTelemetry JS (Optional)
-
-Next, we'll instrument our application using the Splunk Distribution of OpenTelemetry JS 
-by first installing the `@splunk/otel` package: 
+Next, we'll instrument our application using the Splunk Distribution of OpenTelemetry JS
+by first installing the `@splunk/otel` package, so let's install this package as well:
 
 ````
 npm install @splunk/otel
 ````
 
+There's no need to run these commands again as you can use the `package.json` file that 
+was already created. 
+
+### Configure the Splunk Distribution of OpenTelemetry JS 
+
 To configure the instrumentation, we've set the following environment variables:
 
 ````
@@ -80,6 +80,12 @@ AlwaysOn Profiling capabilities.
 
 ### Execute the application
 
+Let's install the packages in the `package.json` file with the following command: 
+
+````
+npm install
+````
+
 Next, we'll execute the application with the `@splunk/otel` package as follows: 
 
 ````

instrumentation/nodejs/linux/index.js

@@ -1,14 +1,32 @@
 const express = require("express");
 const app = express();
 const logger = require('pino')()
+const opentelemetry = require('@opentelemetry/api');
 
 const PORT = process.env.PORT || "8080";
+const tracer = opentelemetry.trace.getTracer('example-app', '0.1.0');
 
 app.get("/hello", (_, res) => {
-  logger.info('/hello endpoint invoked, sending response');
-  res.status(200).send("Hello, World!");
+  hello(res);
 });
 
 app.listen(parseInt(PORT, 10), () => {
   logger.info(`Listening for requests on http://localhost:${PORT}`);
 });
+
+function hello(res) {
+  logger.info('/hello endpoint invoked, sending response');
+  slow_function()
+  res.status(200).send("Hello, World!");
+}
+
+// include a slow function to demonstrate CPU call stacks
+function slow_function() {
+
+  let result = 0;
+  for (let i = 0; i < 1000000000; i++) {
+    result += i;
+  }
+
+  return result;
+}