Since 5.2.3, the ClientSession cannot be injected anymore when transactions are disabled

[panphg]

If MongockStandalone is set up with setTransactionEnabled(false) then the ClientSession is not available for injection anymore in 5.2.3 and 5.2.4, i.e. a migration method with a ClientSession argument fails to be executed.

The following example works until 5.2.2 and fails from 5.2.3 on:

val mongockVersion = ...
implementation("io.mongock:mongock-standalone:$mongockVersion")
implementation("io.mongock:mongodb-sync-v4-driver:$mongockVersion")

MongockStandalone
    .builder()
    .setDriver(MongoSync4Driver.withDefaultLock(mongoClient, dbName))
    .addMigrationScanPackage("my.package")
    .setTransactionEnabled(false)
    .buildRunner()
    .execute()

@ChangeUnit(id = "create-collection", order = "1", author = "x")
class Migration1 {

    @Execution
    fun createCollection(session: ClientSession, db: MongoDatabase) {
            db.createCollection(session, "example")
    }

}

The exception thrown when using 5.2.3:

Caused by: io.mongock.driver.api.common.DependencyInjectionException: Wrong parameter[ClientSession]. Dependency not found.
	at io.mongock.runner.core.executor.ChangeLogRuntimeImpl.lambda$getParameter$1(ChangeLogRuntimeImpl.java:118)
	at java.base@17.0.4.1/java.util.Optional.orElseThrow(Optional.java:403)
	at io.mongock.runner.core.executor.ChangeLogRuntimeImpl.getParameter(ChangeLogRuntimeImpl.java:118)
	at io.mongock.runner.core.executor.ChangeLogRuntimeImpl.getInvokationParameters(ChangeLogRuntimeImpl.java:105)
	at io.mongock.runner.core.executor.ChangeLogRuntimeImpl.runChangeSet(ChangeLogRuntimeImpl.java:77)
	at io.mongock.runner.core.executor.ChangeExecutorBase.executeChangeSetMethod(ChangeExecutorBase.java:392)
	at io.mongock.runner.core.executor.ChangeExecutorBase.rollbackIfPresentAndTrackChangeEntry(ChangeExecutorBase.java:276)
	at io.mongock.runner.core.executor.ChangeExecutorBase.lambda$rollbackProcessedChangeSetsIfApply$4(ChangeExecutorBase.java:180)
	... 

Was this an intentional change or is it a regression?

[osantana85]

Hello @panphg , now it works as expected. We fixed an issue (#604) where Mongock was creating ClientSession even if transactions were not enabled. That ClientSession instance is provided by Mongock in scenarios with transactions enabled and using transactional drivers.

It seems you want to manage your own transactions, but we are not sure that will work as expected. The idea behind Mongock creating and injecting the ClientSession is so Mongock can add its changes(changeLog collection) to the transaction, so the entire migration(your changes and the Mongock tracking) is atomic.

If you still want to manage the transaction(meaning that your changes and Mongock's won't be in the same transaction), you need to inject it as a custom dependency on Mongock setup via the addDependency method.

[panphg]

I suspected something like this. Thanks for the explanation.