MySQL Transactions in Node - mysql

Question

Before I commit anything to the database, I want all my update promises resolve; otherwise, I rollback. In other words, I want atomicity. I suppose I could handle the rollback by deleting out rows, but this has its own risks. I noticed if there is an error in any of the promises, the data still gets updated in database. What am I doing wrong?
I have written a simple program to illustrate the issue.
This is the main process:
const db = require('./db.js');
const async = require('async');
let insertList = [];
for (let i = 0; i<3; i++) {
insertList.push(i);
}
async function func1 () {
return new Promise((resolve, reject) => {
console.log("In Func1");
async.forEachOf(insertList, function(value, key, callback) {
console.log('>>>>' + value + '<<<<<<' + key );
db.insertOne('coll1', {value}).then(() => {
callback();
}).catch(err => {callback(err)})
}, function(err) {
// if any of the file processing produced an error, err would equal that error
if( err ) {
// One of the iterations produced an error.
// All processing will now stop.
console.log('err:', err);
reject(err);
} else {
console.log('Col1 All inserts have been processed successfully');
resolve("Success");
}
});
})
}
function func2 () {
return new Promise((resolve, reject) => {
console.log("In Func2");
async.forEachOf(insertList, function(value, key, callback) {
console.log('>>>>' + value + '<<<<<<' + key );
db.insertOne('coll2', {value}).then(() => {
callback();
}).catch(err => {callback(err)})
}, function(err) {
// if any of the file processing produced an error, err would equal that error
if( err ) {
// One of the iterations produced an error.
// All processing will now stop.
console.log('err:', err);
reject(err);
} else {
console.log('Col2 All inserts have been processed successfully');
resolve("Success");
}
});
})
}
function func3 () {
return new Promise((resolve, reject) => {
console.log("In Func3");
async.forEachOf(insertList, function(value, key, callback) {
console.log('>>>>' + value + '<<<<<<' + key );
if(key === 1) {
value = 'a';
}
db.insertOne('coll3', {value}).then(() => {
callback();
}).catch(err => {callback(err)})
}, function(err) {
// if any of the file processing produced an error, err would equal that error
if( err ) {
// One of the iterations produced an error.
// All processing will now stop.
console.log('err:', err);
reject(err);
} else {
console.log('Col3 All inserts have been processed successfully');
resolve("Success");
}
});
})
}
db.connect().then((pool) => {
pool.getConnection((err, connection) =>{
if (err)
return console.error(err);
else {
}
connection.beginTransaction((err) => {
if (err) {
return console.error(err);
}
let func1Promise = new Promise((resolve, reject) => {func1().then(() => {
console.log("Func1 complete");
resolve("Func1 complete");
}).catch((err) => {
console.error("Func1 ERROR: ", err);
reject("Func1 ERROR: ", err);
})});
let func2Promise = new Promise((resolve, reject) => {func2().then(() => {
console.log("Func2 complete");
resolve("Func2 complete");
}).catch((err) => {
console.error("Func2 ERROR: ", err);
reject("Func2 ERROR: ", err);
})});
let func3Promise = new Promise((resolve, reject) => {func3().then(() => {
console.log("Func3 complete");
resolve("Func3 complete");
}).catch((err) => {
console.error("Func3 ERROR: ", err);
reject("Func3 ERROR: ", err);
})});
Promise.all([func1Promise, func2Promise, func3Promise])
.then(()=> {
console.log("All Processes completed successfully.");
connection.commit(err => {
if (err) {
connection.rollback(() => {
throw err;
});
}
console.log('Commit Complete.');
connection.release();
});
})
.catch((err)=> {
console.error(err);
console.error("An update process has failed.");
connection.rollback(() => {
console.error(err);
connection.release();
});
})
});
})
});
The db.js looks like this:
const mysql = require('mysql');
const config = {
db: {
host: 'localhost',
user: process.env.DBUSER,
password: process.env.DBPASSWORD,
database: 'test',
}
};
var pool;
class DB {
constructor(host, user, password, database) {
this.host = host;
this.user = user;
this.password = password;
this.database = database;
}
connect() {
return new Promise((resolve, reject) => {
pool = mysql.createPool({
connectionLimit: 10,
host : this.host,
user : this.user,
password : this.password,
database : this.database
});
resolve(pool);
});
}
objToArray(obj) {
let arr = obj instanceof Array;
return (arr ? obj : Object.keys(obj)).map((i) => {
let val = arr ? i : obj[i];
if(typeof val === 'object' && val !== null)
return this.objToArray(val);
else
return val;
});
}
insertOne(collection, insertObj) {
return new Promise((resolve, reject) => {
pool.getConnection((err, connection) => {
if (err) {
resolve(err);
} else {
let sql = "INSERT INTO " + collection + " VALUES (?)";
// Convert the array of objects into an array of arrays.
let responseJson = this.objToArray(insertObj);
// The query object expects an array of objects so you pass in 'responseJson' as is
console.log(responseJson);
connection.query(sql, [responseJson], (err, result) => {
if (err) {
console.error(err);
return reject(err);
}
//console.log(result);
resolve("SUCCESS: object inserted into database");
});
}
});
});
}
}
const db = new DB(config.db.host, config.db.user, config.db.password, config.db.database);
Object.freeze(db);
module.exports = db;
My database "test" is simple and consists of 3 tables, coll1, coll2, coll3 and each has on field which is type int. In the third function I replace the 1 with 'a' This causes an error and the code catches this error and attempts a rollback, which does not work. If I set a breakpoint after func1 is executed and check the database, the values are already in the database.
Here is the version of MySQL that I am running:
Variable_name,Value
innodb_version,8.0.11
protocol_version,10
slave_type_conversions,
tls_version,"TLSv1,TLSv1.1,TLSv1.2"
version,8.0.11
version_comment,"MySQL Community Server - GPL"
version_compile_machine,x86_64
version_compile_os,macos10.13
version_compile_zlib,1.2.11
I am using the following NPM packages in node:
"async": "^2.6.2",
"mysql": "^2.15.0"

Answer 1

You're creating a transaction on a connection created in your test program, but your db.js's insertOne is grabbing a new connection from the pool that does not have a transaction. You should be passing in the connection you created in the test program.