lab 05

labs/05/server2/modules/Database.js

@@ -0,0 +1,50 @@
+import mysql from "mysql2/promise";
+
+export class Database {
+  constructor(config) {
+    this.readerPool = this.createPool(config, config.readerUser, config.readerPassword);
+    this.writerPool = this.createPool(config, config.writerUser, config.writerPassword);
+  }
+
+  createPool(config, user, password) {
+    return mysql.createPool({
+      host:               config.host,
+      port:               config.port,
+      database:           config.database,
+      user:               user,
+      password:           password,
+      ssl:                config.ssl,
+      waitForConnections: true,
+      connectionLimit:    5,
+
+      // hand back DATETIME exactly as it is stored instead of a JS Date,
+      // which would otherwise be shifted into UTC on the way to the client
+      dateStrings:        true,
+
+      // chained statements never even reach the database
+      multipleStatements: false,
+    });
+  }
+
+  async testConnections() {
+    const [reader] = await this.readerPool.query("SELECT CURRENT_USER() AS user;");
+    const [writer] = await this.writerPool.query("SELECT CURRENT_USER() AS user;");
+
+    return {
+      reader: reader[0].user,
+      writer: writer[0].user,
+    };
+  }
+
+  // reads go through the user that only holds SELECT
+  async read(statement) {
+    const [rows] = await this.readerPool.query(statement.toString());
+    return rows;
+  }
+
+  // writes go through the user that holds SELECT, INSERT and CREATE, nothing else
+  async write(sql) {
+    const [result] = await this.writerPool.query(sql);
+    return result;
+  }
+}