fix race conditions in check_connect.js

(cherry picked from commit 524ddb96770690455b82522104a543c5b0b1f3b3)

packages/backend/scripts/check_connect.js

@@ -7,9 +7,53 @@ import Redis from 'ioredis';
 import { loadConfig } from '../built/config.js';
 
 const config = loadConfig();
-const redis = new Redis(config.redis);
 
-redis.on('connect', () => redis.disconnect());
-redis.on('error', (e) => {
-	throw e;
-});
+// createPostgresDataSource handels primaries and replicas automatically.
+// usually, it only opens connections first use, so we force it using
+// .initialize()
+async function connectToPostgres(){
+	const source = createPostgresDataSource(config);
+	await source.initialize();
+	await source.destroy();
+}
+
+// Connect to all redis servers
+async function connectToRedis(redisOptions) {
+	return await new Promise(async (resolve, reject) => {
+		const redis = new Redis({
+			...redisOptions,
+			lazyConnect: true,
+			reconnectOnError: false,
+			showFriendlyErrorStack: true,
+		});
+		redis.on('error', e => reject(e));
+
+		try {
+			await redis.connect();
+			resolve();
+
+		} catch (e) {
+			reject(e);
+
+		} finally {
+			redis.disconnect(false);
+		}
+	});
+}
+
+// If not all of these are defined, the default one gets reused.
+// so we use a Set to only try connecting once to each **uniq** redis.
+const promises = Array
+	.from(new Set([
+		config.redis,
+		config.redisForPubsub,
+		config.redisForJobQueue,
+		config.redisForTimelines,
+		config.redisForReactions,
+	]))
+	.map(connectToRedis)
+	.concat([
+		connectToPostgres()
+	]);
+
+await Promise.allSettled(promises);