From 967df825cb31a928c528521e8dc6dec4b80f52f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gast=C3=B3n=20Fournier?= <gaston@getunleash.io>
Date: Wed, 18 Jun 2025 17:40:21 +0200
Subject: [PATCH] feat: do not lock until migrations are needed (#10170)

---
 src/lib/server-impl.ts | 34 +++++++++++++++++++---------------
 src/migrator.ts        | 22 ++++++++++++++++++++++
 2 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/src/lib/server-impl.ts b/src/lib/server-impl.ts
index 54ac5d01b1..21e2cef94a 100644
--- a/src/lib/server-impl.ts
+++ b/src/lib/server-impl.ts
@@ -1,7 +1,7 @@
 import stoppable, { type StoppableServer } from 'stoppable';
 import { promisify } from 'util';
 import version from './util/version.js';
-import { migrateDb, resetDb } from '../migrator.js';
+import { migrateDb, requiresMigration, resetDb } from '../migrator.js';
 import getApp from './app.js';
 import type MetricsMonitor from './metrics.js';
 import { createMetricsMonitor } from './metrics.js';
@@ -336,21 +336,25 @@ async function start(
         if (config.db.disableMigration) {
             logger.info('DB migration: disabled');
         } else {
-            logger.info('DB migration: start');
-            if (config.flagResolver.isEnabled('migrationLock')) {
-                logger.info('Running migration with lock');
-                const lock = withDbLock(config.db, {
-                    lockKey: defaultLockKey,
-                    timeout: defaultTimeout,
-                    logger,
-                });
-                await lock(migrateDb)(config);
-            } else {
-                logger.info('Running migration without lock');
-                await migrateDb(config);
-            }
+            if (await requiresMigration(config)) {
+                logger.info('DB migration: start');
+                if (config.flagResolver.isEnabled('migrationLock')) {
+                    logger.info('Running migration with lock');
+                    const lock = withDbLock(config.db, {
+                        lockKey: defaultLockKey,
+                        timeout: defaultTimeout,
+                        logger,
+                    });
+                    await lock(migrateDb)(config);
+                } else {
+                    logger.info('Running migration without lock');
+                    await migrateDb(config);
+                }
 
-            logger.info('DB migration: end');
+                logger.info('DB migration: end');
+            } else {
+                logger.info('DB migration: no migration needed');
+            }
         }
     } catch (err) {
         logger.error('Failed to migrate db', err);
diff --git a/src/migrator.ts b/src/migrator.ts
index 82027b290b..8543cefb98 100644
--- a/src/migrator.ts
+++ b/src/migrator.ts
@@ -40,6 +40,28 @@ export async function migrateDb(
     });
 }
 
+export async function requiresMigration({
+    db,
+}: Pick<IUnleashConfig, 'db'>): Promise<boolean> {
+    return noDatabaseUrl(async () => {
+        const custom = {
+            ...db,
+            connectionTimeoutMillis: secondsToMilliseconds(10),
+        };
+
+        // disable Intellij/WebStorm from setting verbose CLI argument to db-migrator
+        process.argv = process.argv.filter((it) => !it.includes('--verbose'));
+        const dbm = getInstance(true, {
+            cwd: __dirname,
+            config: { custom },
+            env: 'custom',
+        });
+
+        const pendingMigrations = await dbm.check();
+        return pendingMigrations.length > 0;
+    });
+}
+
 // This exists to ease testing
 export async function resetDb({ db }: IUnleashConfig): Promise<void> {
     return noDatabaseUrl(async () => {