Timefold Solver 2.0 is now live. We realize that a new major version often looks scary and the natural question is how much work is this upgrade actually going to be?
Before asking anyone else to upgrade, we ran the migration playbook on all of our quickstart projects and kept a stopwatch running. Under 10 minutes, all done! No AI was used here, but a coding agent could perhaps make that even faster.
The quickstarts are small, but they cover most of the API surface, and we use them as a test bench for experiments. That makes them a pretty good benchmark for what the upgrade actually feels like.
# The automated migration recipe
When we started on Solver 2.0, one of our goals was to leave some older deprecated APIs behind and clean up the package structure while we were at it. The other goal was to not make any of that your problem.
So we made sure almost all of the changes could be automated. OpenRewrite allowed us to create a recipe to deterministically perform the necessary changes to migrate to Solver 2.0. The same recipe can be used by all our users to run the same migration on their codebases with a single command:
# This blog post is static, check the documentation for the latest versions.
mvn org.openrewrite.maven:rewrite-maven-plugin:6.28.1:run \\
-Drewrite.recipeArtifactCoordinates=ai.timefold.solver:timefold-solver-migration:2.0.0 \\
-Drewrite.activeRecipes=ai.timefold.solver.migration.ToLatest
That one command pulls the latest recipe and upgrades Timefold Solver to 2.0.0. Running it across all quickstart projects took about 3 minutes.
# Where the other 7 minutes went
With still 7 minutes on the clock, this is where the rest of that time went.
# Java 21: < 1 minute
Solver 2.0 moves the Java baseline from 17 to 21. Simple find-and-replace in our build files.
The recipe doesn't change your Java version for you, because plenty of teams are already on something newer. We'd rather not touch that.
# ConstraintCollectors change: ~ 2 minutes
Two of our quickstart projects (Employee Scheduling and Order Picking) used grouping functions in their constraints, which have changed in Solver 2.0. count() and countDistinct() used to return Integer. They now return Long. sum(ToIntFunction) is gone and the recipe migrates this to sum(ToLongFunction).
The recipe rewrites the collector calls themselves, but it can't fix the downstream code that assumed an int return type. The compiler errors are clear enough that we fixed these by hand in a couple of minutes. Pointing a coding agent at them would work just as well.
# Running the tests: ~ 4 minutes
To confirm nothing broke, we ran the tests. With 15 projects and integration tests in the mix, that takes about 4 minutes.
Stop the clock! Green build! Migration Status == COMPLETE.
# What this means for your project
While our quickstarts are small and your project is probably a lot bigger, the automated migration scripts can take you a long way. Only 2 of our 15 quickstart projects needed manual intervention, and even then it was minor.
If you are currently on Timefold Solver 1.x, we encourage you to run the migration recipe and see how far you get. For anything it doesn’t cover (like replacing deprecated APIs with the new alternatives), we have dedicated migration guides to help you or your AI coding agents through the rest!
# Try Plus and Enterprise for free while you're at it
Plus and Enterprise editions now have a free trial. If you've just finished upgrading, you're in the perfect position to see what the solver can do with more of the engine turned on.
For example, the community edition runs on a single thread. Our enterprise version uses every core you give it, which is just a single line of configuration.
<solver>
<moveThreadCount>AUTO</moveThreadCount>
...
</solver>
On a project of any real size, you notice the difference in the first 30 seconds.
Grab a trial license at licenses.timefold.ai, the 2.0 docs walk you through setup.
# A reasonable upgrade plan
Based on how our own upgrade went, you only need 5 steps:
- Get to the latest 1.x release first (we got migration recipes for that, even when coming from OptaPlanner) and run your tests.
- Make sure your build and runtime are on Java 21.
- Run the Timefold Solver 2.0 migration recipe.
- Check for lingering issues and solve them with our manual migration guides.
- Commit, ship, and kick the tires on the Enterprise Solver trial.
In case something doesn't work out for you, reach out to us on Discord or Github Discussions and we'll get you on 2.0 together.
