refactor: Rewrite health check server

src/util/healthCheck.ts

@@ -0,0 +1,49 @@
+import http from "node:http";
+import util from "node:util";
+import type {
+  HealthCheckConfig,
+  HealthCheckServer,
+  HealthCheckStatus,
+  RuntimeResources,
+} from "../types";
+
+const isHealthy = (
+  isHealthSetToOk: boolean,
+  resources: Partial<RuntimeResources>,
+) =>
+  isHealthSetToOk &&
+  resources.producer?.isConnected() &&
+  resources.hfpConsumer?.isConnected() &&
+  resources.partialApcConsumer?.isConnected();
+
+const createHealthCheckServer = (
+  { port }: HealthCheckConfig,
+  resources: Partial<RuntimeResources>,
+): HealthCheckServer => {
+  let isHealthSetToOk = false;
+  let server: http.Server | undefined = http.createServer((req, res) => {
+    if (req.url === "/healthz") {
+      if (isHealthy(isHealthSetToOk, resources)) {
+        res.writeHead(204);
+      } else {
+        res.writeHead(500);
+      }
+    } else {
+      res.writeHead(404);
+    }
+    res.end();
+  });
+  server.listen(port);
+  const setHealth = (status: HealthCheckStatus) => {
+    isHealthSetToOk = status === "ok";
+  };
+  const close = async (): Promise<void> => {
+    if (server && server.listening) {
+      await util.promisify(server.close.bind(server))();
+      server = undefined;
+    }
+  };
+  return { close, setHealth };
+};
+
+export default createHealthCheckServer;