Implicit transaction wrapping fails with UncategorizedMongoDbException on Standalone MongoDB instances

[gwynejsn]

Description

When using Flamingock with Spring Boot auto-configuration and Spring Data MongoDB, Flamingock automatically detects transaction capabilities. If there is a PlatformTransactionManager in the context (for example, introduced by spring-modulith-starter-mongodb), Flamingock implicitly wraps migration pipeline executions inside transactional boundaries.

However, when running against a Standalone MongoDB deployment (which does not support replica sets or transactions), this fails with the following exception:

org.springframework.data.mongodb.UncategorizedMongoDbException: This MongoDB deployment does not support retryable writes. Please add retryWrites=false to your connection string.

Adding retryWrites=false or setting flamingock.transaction-enabled=false in the application configuration properties does not resolve this if MongoDBSpringDataTargetSystem is instantiated, because the driver attempts to initialize transactional sessions regardless of those properties.

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Steps to Reproduce

1. Run a local standalone MongoDB instance (no replica set enabled).
2. Configure a Spring Boot application with both flamingock-mongodb-springdata-targetsystem and spring-modulith-starter-mongodb (which registers a MongoTransactionManager).
3. Set properties in application.properties:

   flamingock.transaction-enabled=false
   spring.mongodb.uri=mongodb://localhost:27017/db?retryWrites=false

4. Start the application context and observe the migration runner failure.

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Expected Behavior

Setting flamingock.transaction-enabled=false should completely bypass the creation of MongoDBSpringDataTxWrapper (or use a no-op implementation) so that migrations can run successfully on standalone database deployments without attempting transaction sessions.

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Current Workaround

Currently, to work around this on a standalone MongoDB instance, developers must override the MongoDBSpringDataTargetSystem bean and inject a custom no-op TransactionWrapper programmatically:

@Bean
public MongoDBSpringDataTargetSystem mongoDBSpringDataTargetSystem(MongoTemplate mongoTemplate) {
    return new MongoDBSpringDataTargetSystem("mongodb-name", mongoTemplate) {
        @Override
        public io.flamingock.internal.core.transaction.TransactionWrapper getTxWrapper() {
            return new io.flamingock.internal.core.transaction.TransactionWrapper() {
                @Override
                public <T> T wrapInTransaction(ExecutionRuntime runtime, Function<ExecutionRuntime, T> function) {
                    return function.apply(runtime); // Bypass transaction creation
                }
            };
        }
    };
}

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Environment Info

• Flamingock Version: 1.4.4
• Spring Boot Version: 3.x / 4.x
• MongoDB Driver Version: 5.x
• MongoDB Server Deployment: Standalone (v6.x / v7.x)

[osantana85]

Hi @gwynejsn,

Thank you for reporting this issue and for providing such a detailed description, reproduction steps, and workaround.

We’ll review the transaction wrapper initialization behavior when flamingock.transaction-enabled=false and we’ll get back to you as soon as possible with our findings.

Thanks again!