Refactor database pool use

backend/src/database.ts

@@ -1,11 +1,14 @@
 import config from './config';
-import { createPool, PoolConnection } from 'mysql2/promise';
+import { createPool, Pool, PoolConnection } from 'mysql2/promise';
 import logger from './logger';
 import { PoolOptions } from 'mysql2/typings/mysql';
 
 export class DB {
-  static poolConfig = ():PoolOptions => {
-    let poolConfig:PoolOptions = {
+  static connectionsReady: number[] = [];
+  static pool: Pool | null = null;
+
+  static poolConfig = (): PoolOptions => {
+    const poolConfig: PoolOptions = {
       port: config.DATABASE.PORT,
       database: config.DATABASE.DATABASE,
       user: config.DATABASE.USERNAME,
@@ -13,9 +16,9 @@ export class DB {
       connectionLimit: 10,
       supportBigNumbers: true,
       timezone: '+00:00',
-    }
+    };
 
-    if (config.DATABASE.SOCKET !== "") {
+    if (config.DATABASE.SOCKET !== '') {
       poolConfig.socketPath = config.DATABASE.SOCKET;
     } else {
       poolConfig.host = config.DATABASE.HOST;
@@ -23,27 +26,27 @@ export class DB {
 
     return poolConfig;
   }
-  
-  static pool = createPool(DB.poolConfig());
 
-  static connectionsReady: number[] = [];
-
-  static async getConnection() {
-    const connection: PoolConnection = await DB.pool.getConnection();
-    const connectionId = connection['connection'].connectionId;
-    if (!DB.connectionsReady.includes(connectionId)) {
-      await connection.query(`SET time_zone='+00:00';`);
-      this.connectionsReady.push(connectionId);
+  static async getPool(): Promise<Pool> {
+    if (DB.pool === null) {
+      DB.pool = createPool(DB.poolConfig());
+      DB.pool.on('connection', function (newConnection: PoolConnection) {
+        newConnection.query(`SET time_zone='+00:00'`);
+      });
     }
-    return connection;
+    return DB.pool;
+  }
+
+  static async query(query, params?) {
+    const pool = await DB.getPool();
+    return pool.query(query, params);
   }
 }
 
 export async function checkDbConnection() {
   try {
-    const connection = await DB.getConnection();
+    await DB.query('SELECT ?', [1]);
     logger.info('Database connection established.');
-    connection.release();
   } catch (e) {
     logger.err('Could not connect to database: ' + (e instanceof Error ? e.message : e));
     process.exit(1);