Docker healthcheck

Copied from https://scoutapm.com/blog/how-to-use-docker-healthcheck

extra/healthcheck.js

@@ -0,0 +1,19 @@
+var http = require("http");
+var options = {
+  host: "localhost",
+  port: "3001",
+  timeout: 2000,
+};
+var request = http.request(options, (res) => {
+  console.log(`STATUS: ${res.statusCode}`);
+  if (res.statusCode == 200) {
+    process.exit(0);
+  } else {
+    process.exit(1);
+  }
+});
+request.on("error", function (err) {
+  console.log("ERROR");
+  process.exit(1);
+});
+request.end();