Don't reuse closed or mismatched MariaDB clients

grabMariaDBClient reused global.MARIADB_CLIENT whenever the requested
config matched global.CONFIG. It never checked that the client was made
from that config or was still open. init() sets global.CONFIG before
creating the client, so a re-init after a close, or a config change, got
back a closed or wrong client.

- Remember the cache key each client was created with, and compare that
- Wrapping close() drops the client from the cache and unsets
  global.MARIADB_CLIENT, so the next grab or ensureInit makes a new one
- resolveClient goes through grabMariaDBClient instead of repeating the
  global.CONFIG comparison
- Remove the queue test's workaround for this

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/functions/grab-mariadb-client.test.ts

@@ -0,0 +1,38 @@
+import { afterEach, expect, test } from "bun:test";
+import grabMariaDBClient from "./grab-mariadb-client";
+import setMariaDBClient from "./set-mariadb-client";
+
+// Clients connect lazily, so none of these open a connection
+const config = { db_name: "bmt_client_cache", ssl_reject_unauthorized: false };
+
+const originalConfig = global.CONFIG;
+
+afterEach(async () => {
+    await global.MARIADB_CLIENT?.close();
+    global.CONFIG = originalConfig;
+});
+
+test("reuses the client for the same config", () => {
+    expect(grabMariaDBClient({ config })).toBe(grabMariaDBClient({ config: { ...config } }));
+});
+
+test("a closed client is dropped from the cache and the global slot", async () => {
+    setMariaDBClient({ config });
+    const first = global.MARIADB_CLIENT!;
+
+    await first.close();
+    expect(global.MARIADB_CLIENT).toBeUndefined();
+
+    const second = grabMariaDBClient({ config });
+    expect(second).toBeDefined();
+    expect(second).not.toBe(first);
+});
+
+test("the global client is not reused for a different config", () => {
+    setMariaDBClient({ config });
+    global.CONFIG = { db_name: "bmt_other" };
+
+    const other = grabMariaDBClient({ config: global.CONFIG });
+    expect(other).not.toBe(global.MARIADB_CLIENT);
+    other?.close();
+});

src/functions/grab-mariadb-client.ts

@@ -10,6 +10,9 @@ type Params = {
 /** Reuse one client per distinct connection config to avoid exhausting MariaDB connections. */
 const clientCache = new Map<string, Bun.SQL>();
 
+/** Cache key each client was created with */
+const clientKeys = new WeakMap<Bun.SQL, string>();
+
 /**
  * Cache key covering everything that affects the connection, not just the
  * database name.
@@ -36,8 +39,7 @@ export default function grabMariaDBClient({
     // Prefer the process-wide client when it was created from the same config
     if (
         global.MARIADB_CLIENT &&
-        global.CONFIG &&
-        mariadbClientCacheKey(global.CONFIG) === cacheKey
+        clientKeys.get(global.MARIADB_CLIENT) === cacheKey
     ) {
         clientCache.set(cacheKey, global.MARIADB_CLIENT);
         return global.MARIADB_CLIENT;
@@ -71,6 +73,22 @@ export default function grabMariaDBClient({
             adapter: "mariadb",
         } as Bun.SQL.Options);
 
+        /**
+         * A closed client can't run queries, so forget it on close: the next
+         * grab (or `ensureInit`) creates a fresh one.
+         */
+        const close = MariaDBClient.close.bind(MariaDBClient);
+        MariaDBClient.close = (...args: Parameters<Bun.SQL["close"]>) => {
+            if (clientCache.get(cacheKey) === MariaDBClient) {
+                clientCache.delete(cacheKey);
+            }
+            if (global.MARIADB_CLIENT === MariaDBClient) {
+                global.MARIADB_CLIENT = undefined;
+            }
+            return close(...args);
+        };
+
+        clientKeys.set(MariaDBClient, cacheKey);
         clientCache.set(cacheKey, MariaDBClient);
         return MariaDBClient;
     } catch (error: any) {

src/functions/init.ts

@@ -19,7 +19,8 @@ import {
 declare global {
     var CONFIG: BunMariaDBConfig;
     var DB_SCHEMA: BUN_MARIADB_DatabaseSchemaType;
-    var MARIADB_CLIENT: Bun.SQL;
+    /** Unset after the client is closed */
+    var MARIADB_CLIENT: Bun.SQL | undefined;
     var CONFIG_FILE_PATH: string;
     var SCHEMA_FILE_PATH: string;
 }

src/lib/db-handler.ts

@@ -1,6 +1,4 @@
-import grabMariaDBClient, {
-    mariadbClientCacheKey,
-} from "../functions/grab-mariadb-client";
+import grabMariaDBClient from "../functions/grab-mariadb-client";
 import type {
     BunMariaDBConfig,
     DBInsertReturn,
@@ -29,16 +27,7 @@ export function resolveClient(config?: BunMariaDBConfig): Bun.SQL | undefined {
         return global.MARIADB_CLIENT;
     }
 
-    // Same connection config as the global client → reuse it
-    if (
-        global.MARIADB_CLIENT &&
-        (!global.CONFIG ||
-            mariadbClientCacheKey(config) ===
-                mariadbClientCacheKey(global.CONFIG))
-    ) {
-        return global.MARIADB_CLIENT;
-    }
-
+    // Returns the global client when it was created from the same config
     return grabMariaDBClient({ config });
 }
 

tests/queue.test.ts

@@ -52,20 +52,10 @@ describe.skipIf(!TEST_DB)("Queue tables", () => {
         const createDBSchema = (await import("../src/lib/schema/create-db-schema")).default;
         const appendDefaults = (await import("../src/utils/append-default-fields-to-db-schema")).default;
 
-        /**
-         * The test container uses a self-signed certificate. `db_config` gives
-         * this file its own client, since other test files close theirs. The
-         * client is created before `global.CONFIG` changes, so the previous
-         * file's closed global client isn't reused.
-         */
-        const config = {
-            db_name: TEST_DB!,
-            ssl_reject_unauthorized: false,
-            db_config: { max: 10 },
-        };
-        setMariaDBClient({ config });
-        global.CONFIG = config;
+        // The test container uses a self-signed certificate
+        global.CONFIG = { db_name: TEST_DB!, ssl_reject_unauthorized: false };
         global.DB_SCHEMA = schema;
+        setMariaDBClient({ config: global.CONFIG });
 
         DB = (await import("../src/index")).default;