Write /tmp/app-initialized from Fastboot-side

Author: kzys

fastboot.js

@@ -1,10 +1,35 @@
+/* eslint-disable no-console */
+
 'use strict';
 
+const fs = require('fs');
 const FastBootAppServer = require('fastboot-app-server');
 
+// because fastboot-app-server uses cluster, but it might change in future
+const cluster = require('cluster');
+
+function writeAppInitializedWhenReady() {
+    let timeout;
+
+    timeout = setInterval(function() {
+        console.log('waiting backend');
+        if (fs.existsSync('/tmp/backend-initialized')) {
+            console.log('backend is up. let heroku know the app is ready');
+            fs.writeFileSync('/tmp/app-initialized', 'hello');
+            clearInterval(timeout);
+        } else {
+            console.log('backend is still not up');
+        }
+    }, 1000);
+}
+
 let server = new FastBootAppServer({
     distPath: 'dist',
     port: 9000,
 });
 
+if (!cluster.isWorker) {
+    writeAppInitializedWhenReady();
+}
+
 server.start();

src/bin/server.rs

@@ -102,8 +102,8 @@ fn main() {
     // Creating this file tells heroku to tell nginx that the application is ready
     // to receive traffic.
     if heroku {
-        println!("Writing to /tmp/app-initialized");
-        File::create("/tmp/app-initialized").unwrap();
+        println!("Writing to /tmp/backend-initialized");
+        File::create("/tmp/backend-initialized").unwrap();
     }
 
     // Block the main thread until the server has shutdown