feat: Implement a new Dockerized PostgreSQL data synchronization service with cron scheduling.

sync/db.js

@@ -0,0 +1,41 @@
+'use strict';
+const { Pool } = require('pg');
+
+let srcPool = null;
+let dstPool = null;
+
+function getSrc() {
+  if (!srcPool) {
+    srcPool = new Pool({
+      host:     process.env.SRC_HOST,
+      port:     parseInt(process.env.SRC_PORT) || 5432,
+      database: process.env.SRC_DB,
+      user:     process.env.SRC_USER,
+      password: process.env.SRC_PASS,
+      max: 3,
+      connectionTimeoutMillis: 10000,
+    });
+  }
+  return srcPool;
+}
+
+function getDst() {
+  if (!dstPool) {
+    dstPool = new Pool({
+      host:     process.env.DST_HOST,
+      port:     parseInt(process.env.DST_PORT) || 5432,
+      database: process.env.DST_DB,
+      user:     process.env.DST_USER,
+      password: process.env.DST_PASS,
+      max: 5,
+    });
+  }
+  return dstPool;
+}
+
+async function closeAll() {
+  if (srcPool) { await srcPool.end(); srcPool = null; }
+  if (dstPool) { await dstPool.end(); dstPool = null; }
+}
+
+module.exports = { getSrc, getDst, closeAll };