docs: updates expressjs. Change go link. [sc-00] (#1018)

site/content/docs/open-telemetry/instrumenting-code/_index.md

@@ -76,6 +76,13 @@ Below you will find instructions on how to instrument your popular languages and
 	img="/docs/images/integrations/otel/otel-languages/nextjs_icon.svg"
 	link="/docs/open-telemetry/instrumenting-code/nextjs/"
 >}}
+{{< doc-card
+	class="three-column-card"
+	headerTag="h3"
+	title="Express.js"
+	img="/docs/images/integrations/otel/otel-languages/expressjs_icon.svg"
+	link="/docs/open-telemetry/instrumenting-code/express/"
+>}}
 {{< doc-card
 	class="three-column-card"
 	headerTag="h3"

site/content/docs/open-telemetry/instrumenting-code/express.md

@@ -0,0 +1,113 @@
+---
+title: Express
+weight: 38
+menu:
+  integrations:
+    parent: "Instrumenting your code with OpenTelemetry"
+beta: true
+---
+
+This guide will help you instrument your Express application(s) with OpenTelemetry and send traces to Checkly.
+<!--more-->
+The steps are largely the same as instrumenting any Node.js application with OpenTelemetry.
+## Step 1: Install the OpenTelemetry packages
+
+Install the relevant OpenTelemetry packages:
+
+```bash
+npm install --save \
+    @opentelemetry/sdk-node \
+    @opentelemetry/exporter-trace-otlp-proto \
+    @opentelemetry/auto-instrumentations-node \
+    @opentelemetry/sdk-trace-base \
+    @opentelemetry/api
+```
+
+## Step 2: Initialize the instrumentation
+
+Create a file called `tracing.js` at the root of your project and add the following code:
+
+```javascript
+// tracing.js
+const { NodeSDK } = require('@opentelemetry/sdk-node')
+const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-proto')
+const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node')
+const { BatchSpanProcessor, SamplingDecision } = require('@opentelemetry/sdk-trace-base')
+const { trace } = require('@opentelemetry/api')
+
+const exporter = new OTLPTraceExporter({
+  timeoutMillis: 2000,
+})
+
+const sdk = new NodeSDK({
+  instrumentations: [getNodeAutoInstrumentations()],
+  spanProcessors: new BatchSpanProcessor(exporter),
+  sampler: {
+    shouldSample: (context, traceId, spanName, spanKind, attributes, links) => {
+      const isChecklySpan = trace.getSpan(context)?.spanContext()?.traceState?.get('checkly')
+      if (isChecklySpan) {
+        return { decision: SamplingDecision.RECORD_AND_SAMPLED }
+      } else {
+        return { decision: SamplingDecision.NOT_RECORD }
+      }
+    },
+  },
+})
+
+sdk.start()
+
+process.on('SIGTERM', () => {
+  sdk.shutdown()
+    .then(() => console.log('OTel Tracing terminated'))
+    .catch((error) => console.log('Error terminating OTel tracing', error))
+    .finally(() => process.exit(0))
+})
+```
+
+Notice the `sampler` configuration. This is a custom, **head-based sampler** that will only sample spans that are generated by Checkly by
+inspecting the trace state. This way you only pay for the egress traffic generated by Checkly and not for any other traffic.
+
+## Step 3: Start your app with the instrumentation
+
+
+{{< markdownpartial "/_shared/otel-api-and-endpoint.md" >}}
+
+Then start your app with the extra `-r` flag to load the `tracing.js` file before any other files are loaded. In this case
+the `index.js` file holds your Express app and typically starts with code like:
+
+```javascript
+// index.js
+const express = require('express')
+const PORT = process.env.PORT || '5555'
+const app = express()
+// etc.
+```
+
+```bash
+node -r ./tracing.js index.js
+```
+🎉 You are done. Any interactions with your app that are triggered by a Checkly synthetic monitoring check will now generate
+traces, which are sent back to Checkly and displayed in the Checkly UI.
+
+## Reducing noise in the auto Node.js instrumentation
+
+We found the Node.js auto-instrumentation a bit noisy. There can be a lot of file i/o and a ton of DNS calls you might not
+be interested in. Luckily, you can easily tweak that by providing some extra options to the `getNodeAutoInstrumentations()` function.
+We use the following configuration to filter out some of the noise:
+
+```javascript
+instrumentations: [getNodeAutoInstrumentations({
+  '@opentelemetry/instrumentation-fs': {
+    enabled: false,
+  },
+  '@opentelemetry/instrumentation-net': {
+    enabled: false,
+  },
+  '@opentelemetry/instrumentation-dns': {
+    enabled: false,
+  },
+  '@opentelemetry/instrumentation-http': {
+    enabled: true,
+  },
+})]
+```

site/content/docs/open-telemetry/instrumenting-code/go.md

@@ -1,5 +1,5 @@
 ---
-title: Go
+title: Go / Golang
 head:
   title: "Instrumenting Go with OpenTelemetry"
 metatags: