kubewatcher example: send watch updates to slack (#96)

This example sends change events from a watch to a Slack webhook.

examples/nodejs/kubeEventsSlack.js

@@ -0,0 +1,63 @@
+'use strict';
+
+//
+// Watch kubernetes events and send them to a slack channel.  This
+// uses Slack's incoming webhooks.  To use this, create an incoming
+// webhook for your slack channel through Slack's UI, and populate the
+// relative path below.
+//
+// Create the function in fission:
+//
+//   fission fn create --name kubeEventsSlack --env nodejs --code kubeEventsSlack.js
+//
+// Then, watch all services in the default namespace:
+// 
+//   fission watch create --function kubeEventsSlack --type service --ns default
+//
+
+let https = require('https');
+
+const path = "YOUR RELATIVE PATH HERE", // Something like "/services/XXX/YYY/zZz123"
+
+function upcaseFirst(s) {
+    return s.charAt(0).toUpperCase() + s.slice(1).toLowerCase();
+}
+
+function sendSlackMessage(msg, cb) {
+    let postData = `{"text": "${msg}"}`;
+    let options = {
+        hostname: "hooks.slack.com",
+        path: slackWebhookPath,
+        method: "POST",
+        headers: {
+            "Content-Type": "application/json"
+        }
+    };
+    let req = https.request(options, function(res) {
+        console.log(`slack request status = ${res.statusCode}`);
+        cb();
+    });
+    req.write(postData);
+    req.end();
+}
+
+module.exports = function(context, callback) {
+    console.log(context.request.headers);
+    
+    let obj = context.request.body;
+    let version = obj.metadata.resourceVersion;
+    let eventType = context.request.get('X-Kubernetes-Event-Type');
+    let objType = context.request.get('X-Kubernetes-Object-Type');
+
+    let msg = `${upcaseFirst(eventType)} ${objType} ${obj.metadata.name}`;
+    console.log(msg, version);
+
+    if (eventType == 'DELETED' || eventType == 'ADDED') {
+        console.log("sending event to slack")
+        sendSlackMessage(msg, function() {
+            callback(200, "");
+        });
+    } else {
+        callback(200, "");
+    }
+}