Refactored the DB class into a regular singleton class.

backend/src/api/database-migration.ts

@@ -1,5 +1,5 @@
 import config from '../config';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 
 const sleep = (ms: number) => new Promise(res => setTimeout(res, ms));

backend/src/api/liquid/elements-parser.ts

@@ -2,7 +2,7 @@ import { IBitcoinApi } from '../bitcoin/bitcoin-api.interface';
 import bitcoinClient from '../bitcoin/bitcoin-client';
 import bitcoinSecondClient from '../bitcoin/bitcoin-second-client';
 import { Common } from '../common';
-import { DB } from '../../database';
+import DB from '../../database';
 import logger from '../../logger';
 
 class ElementsParser {

backend/src/api/pools-parser.ts

@@ -1,5 +1,4 @@
-import { readFileSync } from 'fs';
+import DB from '../database';
-import { DB } from '../database';
 import logger from '../logger';
 import config from '../config';
 

backend/src/api/statistics.ts

@@ -1,5 +1,5 @@
 import memPool from './mempool';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 
 import { Statistic, TransactionExtended, OptimizedStatistic } from '../mempool.interfaces';

backend/src/database.ts

@@ -3,52 +3,49 @@ import { createPool, Pool, PoolConnection } from 'mysql2/promise';
 import logger from './logger';
 import { PoolOptions } from 'mysql2/typings/mysql';
 
-export class DB {
+ class DB {
-  static connectionsReady: number[] = [];
+  constructor() {
-  static pool: Pool | null = null;
-
-  static poolConfig = (): PoolOptions => {
-    const poolConfig: PoolOptions = {
-      port: config.DATABASE.PORT,
-      database: config.DATABASE.DATABASE,
-      user: config.DATABASE.USERNAME,
-      password: config.DATABASE.PASSWORD,
-      connectionLimit: 10,
-      supportBigNumbers: true,
-      timezone: '+00:00',
-    };
-
     if (config.DATABASE.SOCKET !== '') {
-      poolConfig.socketPath = config.DATABASE.SOCKET;
+      this.poolConfig.socketPath = config.DATABASE.SOCKET;
     } else {
-      poolConfig.host = config.DATABASE.HOST;
+      this.poolConfig.host = config.DATABASE.HOST;
     }
+  }
+  private pool: Pool | null = null;
+  private poolConfig: PoolOptions = {
+    port: config.DATABASE.PORT,
+    database: config.DATABASE.DATABASE,
+    user: config.DATABASE.USERNAME,
+    password: config.DATABASE.PASSWORD,
+    connectionLimit: 10,
+    supportBigNumbers: true,
+    timezone: '+00:00',
+  };
 
-    return poolConfig;
+  public async query(query, params?) {
+    const pool = await this.getPool();
+    return pool.query(query, params);
   }
 
-  static async getPool(): Promise<Pool> {
+  public async checkDbConnection() {
-    if (DB.pool === null) {
+    try {
-      DB.pool = createPool(DB.poolConfig());
+      await this.query('SELECT ?', [1]);
-      DB.pool.on('connection', function (newConnection: PoolConnection) {
+      logger.info('Database connection established.');
+    } catch (e) {
+      logger.err('Could not connect to database: ' + (e instanceof Error ? e.message : e));
+      process.exit(1);
+    }
+  }
+
+  private async getPool(): Promise<Pool> {
+    if (this.pool === null) {
+      this.pool = createPool(this.poolConfig);
+      this.pool.on('connection', function (newConnection: PoolConnection) {
         newConnection.query(`SET time_zone='+00:00'`);
       });
     }
-    return DB.pool;
+    return this.pool;
-  }
-
-  static async query(query, params?) {
-    const pool = await DB.getPool();
-    return pool.query(query, params);
   }
 }
 
-export async function checkDbConnection() {
+export default new DB();
-  try {
-    await DB.query('SELECT ?', [1]);
-    logger.info('Database connection established.');
-  } catch (e) {
-    logger.err('Could not connect to database: ' + (e instanceof Error ? e.message : e));
-    process.exit(1);
-  }
-}

backend/src/index.ts

@@ -5,7 +5,7 @@ import * as WebSocket from 'ws';
 import * as cluster from 'cluster';
 import axios from 'axios';
 
-import { checkDbConnection, DB } from './database';
+import DB from './database';
 import config from './config';
 import routes from './routes';
 import blocks from './api/blocks';
@@ -89,7 +89,7 @@ class Server {
     diskCache.loadMempoolCache();
 
     if (config.DATABASE.ENABLED) {
-      await checkDbConnection();
+      await DB.checkDbConnection();
       try {
         if (process.env.npm_config_reindex != undefined) { // Re-index requests
           const tables = process.env.npm_config_reindex.split(',');

backend/src/repositories/BlocksRepository.ts

@@ -1,5 +1,5 @@
-import { BlockExtended, PoolTag } from '../mempool.interfaces';
+import { BlockExtended } from '../mempool.interfaces';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 import { Common } from '../api/common';
 import { prepareBlock } from '../utils/blocks-utils';

backend/src/repositories/HashratesRepository.ts

@@ -1,5 +1,5 @@
 import { Common } from '../api/common';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 import PoolsRepository from './PoolsRepository';
 

backend/src/repositories/PoolsRepository.ts

@@ -1,6 +1,6 @@
 import { Common } from '../api/common';
 import config from '../config';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 import { PoolInfo, PoolTag } from '../mempool.interfaces';
 

backend/src/tasks/pools-updater.ts

@@ -1,7 +1,7 @@
 const https = require('https');
 import poolsParser from '../api/pools-parser';
 import config from '../config';
-import { DB } from '../database';
+import DB from '../database';
 import logger from '../logger';
 
 /**