Allow newer migrations to exist and be skipped by validateOnMigrate

[adrianchung]

Since flyway 3.0, the validateOnMigrate is set to true by default. This causes problems with our blue-green deployment strategy.

Scenario:

• Old code running on EC2 instance, running on schema version 10
• Bring up new EC2 instance, running on schema version 11, database is now upgraded. At this point, both the old and the new code is running simultaneously.
• Restart services on old EC2 instance, or start a new EC2 instance using the old code (perhaps done through autoscaling groups).

In this scenario, we won't be able to restart the services on the old EC2 instance because it will detect version 11 of the schema has been applied. An exception message like: Caused by: org.flywaydb.core.api.FlywayException: Validate failed. Found differences between applied migrations and available migrations: Detected applied migration missing on the classpath: 11.

All of our schema changes are backwards compatible, so it'd be nice if we can set an option to ignore detecting newer schema versions.

I realize there is a 'target' property, but that is less than ideal because I don't want to update that every time I add a new schema change.

Ideally, I'd have a property that I can set to just ignore newer schema versions detected, but continue to validate the checksums of schemas up to the the latest applied version in code.

[axelfontaine]

Hi Adrian,

thanks for the suggestion. Yes, this makes sense. This is actually already available for failed migrations, but not for successful ones. Maybe the existing property could simply be generalized.

Cheers
Axel