Deadlock on multiple transactions

What are you doing?

const Sequelize = require('sequelize');
const sequelize = new Sequelize('mysql://user:password@dburl:3306/test')

class TestUser extends Sequelize.Model {}
TestUser.init({
  username: Sequelize.STRING,
  birthday: Sequelize.DATE
}, { sequelize, modelName: 'testuser' })

for (var i = 0; i < 5; i++) {
    sequelize.transaction(t => {
        return TestUser.findOne({
            where: { username: 'janedoe' }
        }, { transaction: t })
        .then(user => {
            return TestUser.update(
                { birthday: new Date(1980, 1, 8) },
                {
                    where: { username: 'janedoe' }
                },
                { transaction: t }
            )
        })
    })
    .then(() => console.log('done'))
    .catch(err => console.log(err))
}

The loop is to mimic consecutive requests to a server. Adjusting the loop count below the connection pool max (default is 5) stops the problem.

To Reproduce Steps to reproduce the behavior:

1. Run the quick example in the documentation (to create an entry)
2. Run the code above
3. See all of updates above fail

What do you expect to happen?

Update the entry successfully.

What is actually happening?

Executing (acafd742-e1e0-4181-be35-ded526d3d4d6): START TRANSACTION;
Executing (358028a0-3206-4262-b96a-f06f9359ecb8): START TRANSACTION;
Executing (eb448c6b-2098-499c-8d60-b6b4c83b2c23): START TRANSACTION;
Executing (cd0d76fc-78a0-4799-bcce-82451fcc38fd): START TRANSACTION;
Executing (23e9b61e-91ab-4764-85a3-98893e0d0f5a): START TRANSACTION;
Executing (acafd742-e1e0-4181-be35-ded526d3d4d6): ROLLBACK;
Executing (358028a0-3206-4262-b96a-f06f9359ecb8): ROLLBACK;
Executing (eb448c6b-2098-499c-8d60-b6b4c83b2c23): ROLLBACK;
Executing (cd0d76fc-78a0-4799-bcce-82451fcc38fd): ROLLBACK;
Executing (23e9b61e-91ab-4764-85a3-98893e0d0f5a): ROLLBACK;
{ SequelizeConnectionAcquireTimeoutError: Operation timeout
...

Environment

Dialect:

• mysql
• postgres
• sqlite
• mssql
• any

Dialect library version: 1.6.5 Database version: 5.7.24 Sequelize version: 5.8.7 Node Version: 8.12.0 OS: Linux 4.19.23-gentoo (x86_64) If TypeScript related: TypeScript version: N/A

Tested with latest release:

• No
• Yes, specify that version: 5.8.7

[agirorn]

I believe I have a workaround using p-queue.

const Sequelize = require('sequelize');
const {default: PQueue} = require('p-queue');
const sequelize = new Sequelize('mysql://user:password@dburl:3306/test')

const sequelize.queue = new PQueue({concurrency: (sequelize.connectionManager.pool.maxSize -1)});
const inTransaction = fn => sequelize.queue.add(
  () => sequelize.transaction((transaction) => fn(transaction)),
);

class TestUser extends Sequelize.Model {}
TestUser.init({
  username: Sequelize.STRING,
  birthday: Sequelize.DATE
}, { sequelize, modelName: 'testuser' })

for (var i = 0; i < 5; i++) {
    inTransaction(t => {
        return TestUser.findOne({
            where: { username: 'janedoe' }
        }, { transaction: t })
        .then(user => {
            return TestUser.update(
                { birthday: new Date(1980, 1, 8) },
                {
                    where: { username: 'janedoe' }
                },
                { transaction: t }
            )
        })
    })
    .then(() => console.log('done'))
    .catch(err => console.log(err))
}

Maybe this could be worked into Sequelize.transaction() so that it works out of the box.

[mycoboco]

Thanks for your reply, @papb. I’m glad to hear that you consider this what should be handled by Sequelize and looking forward to the day I can send a bunch of requests without worry about queueing.