System migrations don't respect transaction settings

[Piotr Adamski]

Description

Running migrations with mongock (with transactions disabled on driver and runner level) against a database that migrations haven't been run before fails with error

ERROR starting session. If Mongock is connected to a MongoDB cluster which doesn't support transactions, you must to disable transactions

PRIORITY

CRITICAL

Version and environment

Mongock

• Mongock version : 5.2.2
• Modules involved(springboot, standalone, MongoDB, DynamoDB, etc.) : standalone
• How Mongock is used(builder or annotation approach, etc.) : builder

Environment

• mongo-java-driver: 3.8.2
• mongo 5.0.7

Steps to Reproduce

1. Take the example standalone runner project and disable transactions (driver.disableTransaction() and MongockStandalone.builder().setTransactionEnabled(false).setTransactionStrategy(TransactionStrategy.EXECUTION))
2. Run migrations against the database using mongo client or mongo server instance that does not allow transactions

Behaviour

Expected behavior:

Migrations run successfuly

Actual behavior:

Execution fails with error

ERROR starting session. If Mongock is connected to a MongoDB cluster which doesn't support transactions, you must to disable transactions

How often the bug happens:

Every time

Additional context

I believe it is happening because:

• system change unit is transactional (default value of the annotation) https://github.com/mongock/mongock/blob/develop/mongock-core/mongock-runner/mongock-runner-core/src/main/java/io/mongock/runner/core/executor/system/changes/SystemChangeUnit00001.java#L19
• system update executor ignores configuration and uses fixed value of the transaction strategy https://github.com/mongock/mongock/blob/develop/mongock-core/mongock-runner/mongock-runner-core/src/main/java/io/mongock/runner/core/executor/system/SystemUpdateExecutor.java#L48
• routine that prepares session for the transactions is executed because isStrategyPerChangeUnit() && changeLog.isTransactional() evaluates to true because of the above https://github.com/mongock/mongock/blob/develop/mongock-core/mongock-runner/mongock-runner-core/src/main/java/io/mongock/runner/core/executor/ChangeExecutorBase.java#L116

[Antonio Perez Diepa]

Hello @mcveat ,

We'll take a look at this soon. Probably Monday evening.

Thanks

[Oliver Santana]

Hello @mcveat , we've just released Mongock's version 5.2.4, which fixes this issue. Please could you try it and let us know? Thanks.

[Piotr Adamski]

Thanks @osantana85 , I hope to find time to try it sometime this or next week, will let you know