How to retry transactions in Sequelize

Anonyma — Wed, 13 May 2020 22:00:30 +0000

You might be getting errors like "SequelizeDatabaseError: Deadlock found when trying to get lock; try restarting transaction" and wondering how you could restart the transaction as indicated.

(Yeah, you could always catch the error manually, stringify it and look for a substring, but then you would have to check for every possible error you want to retry the query for in every catch clause - and we want our code to be DRY)

This behaviour can be natively enabled by adding a retry object to the list of options provided when initializing Sequelize:

const sequelize = new Sequelize(process.env.REMOTE_DB_NAME, 
    process.env.REMOTE_DB_NAME, 
    process.env.REMOTE_DB_PW, 
    {
    host: process.env.REMOTE_DB_HOST,
    dialect: 'mysql',
    // Here:
    retry: {
        match: [Sequelize.ConnectionError]
    }
})

As you can see, we can pass native Sequelize errors to the match array.

Now you might be thinking "Ok, but the deadlock error is actually a “SequelizeDatabaseError” - so how can we specifically filter that one out?"
Well, the retry option also happens to accept regex parameters!

retry: {
        match: [/Deadlock/i],
        max: 3
    }}

As seen above, we can specify the maximum number of retries to execute (max).

The match array also accepts strings, so here's a full example showing all valid error formats:

retry: {
    match: [
        Sequelize.ConnectionError,
        Sequelize.ConnectionTimedOutError,
        Sequelize.TimeoutError,
        /Deadlock/i,
        'SQLITE_BUSY'],
    max: 3
}

(Note that neither regexes nor Sequelize errors are passed as strings)

You can find the full list of Sequelize errors here:
https://sequelize.org/v5/identifiers.html#errors
(Bonus) And here’s the full list of options you can pass to retry: https://github.com/mickhansen/retry-as-promised/blob/master/README.md

Feel free to hit me up on Twitter if you have any further questions! @Anonyma_Z

DEV Community: Anonyma

How to retry transactions in Sequelize