Longevity 0.26 - Migrations Framework

Longevity release 0.26 is out, and features the initial version of a schema migrations framework. You might ask, "Why would longevity - a persistence framework for Scala and NoSQL - require its own migrations framework? Couldn't it use any number of existing tools for doing schema migrations?"

Because longevity handles persistence for you, allowing you to write you application in terms of your domain model, the traditional approach to migrating schema with database scripts does not always work out. At present, every back end stores your persistent objects in JSON. Back ends such as SQLite and Cassandra store the JSON in regular text columns. MongoDB offers update commands that allow you to modify your BSON documents dynamically, so a more traditional approach to schema migrations may work for you. It’s also possible that we will be adding column-based back ends for SQLite and Cassandra in the future, which will also be amenable to more traditional approaches.

But even if a database-oriented tool such as FlywayDB works for you, we still want to provide you with an option that raises schema migrations up to the domain model abstraction layer. With longevity migrations, you define your domain model evolution in terms of Scala functions that map from the old version of the domain to the new version. So no database scripts are needed.

I'm excited about this release because the lack of tools to help migrate a schema was, in my mind, the last major showstopper for using longevity in a production environment. Domain models do evolve, and we need to be able to bring existing data along with the changes. It's a pretty bare bones implementation of a migrations framework, but it's entirely functional, and I have a long list of ideas on ways to improve it.

My favorite feature by far on the wish list, I've been calling soft-stop migrations. If our migrations are defined in terms of Scala, that gives us the opportunity to keep both versions of the schema alive in the database simultaneously. While we migrate from one version to another, applications running the old version can use those Scala functions to keep the new version up to date with ongoing changes. This way, the application can continue running throughout the process of a schema migration. This kind of thing is very difficult to do when your migration scripts are written in a database query language. And limiting downtime is highly desirable. It would also be relatively easy to implement, and I'm tempted to do it. But now that I have a basic schema migrations tool in place, I'd like to focus on replacing home-grown reflective code with shapeless for a while.

Check out the chapter on migrations in the user manual to get a feel for how it works.

Longevity Goes Finally Tagless

Longevity - your persistence framework for Scala and NoSQL - has always sported a future-based API. But now in release 0.24, longevity has gone finally tagless, replacing the hardcoded references to scala.concurrent.Future with a generic effect F. We currently support three effects: Scala futures, the cats-effect IO monad, and an old-fashioned blocking API for the purists out there. We plan to support a variety of Task monads as effects in the near future, and you can always write your own effect as well.

For more information on longevity effects, see the user manual.

For examples on how longevity works with different effects, check out this demo code.

This release is exciting for me for many reasons. Perhaps most importantly, longevity now sports a truly functional API with support for IO monads. But the flexibility of the finally tagless approach is truly freeing. We can satisfy the purist functional programmers, and continue to support people who want to do reactive programming with futures, with a minimum of cognitive overhead. It's also exciting to me because it's a major step on my personal path to becoming a better functional programmer.

But the best part for me is just how beautiful the repository API has become. Just look at it. In a sense, this is how this API was always meant to be. Perfectly intuitive, fully typesafe, just the right level of abstraction without a hint of leaks. I couldn't imagine doing persistence in Scala any other way.

Longevity now has Better Support for Alternative JDBC Back Ends

Longevity release 0.21 features a new back end called JDBC. It should work in a lot of situations where using SQLite back end with a non-SQLite driver would fail. There is also a much easier development path for creating your own back end, should the generic JDBC back end not be sufficient.

New SQLite Back End for Longevity

Longevity release 0.20.0 is out, featuring the following changes:

• Added a SQLite back end.
• Trying to be a bit more formal, changed occurrences of "Mongo" with "MongoDB" in the public API.
• Replaced "partition key" terminology with "primary key". I was undecided about this for a long time leading up to implementing the feature, and I think I made the wrong choice when the time came. "Partition key" is a little over specified for distributed database scenario. It's a little more general to posit that a database table can have multiple keys, but can more powerfully optimize a single one of those keys at your choosing. Now that I have three very different back ends, it's getting harder and harder to overfit longevity to a single database technology!

Keep reading to learn more about the new back end:

More Longevity Awesomeness with Macro Annotations!

I just got longevity release 0.18 out and wow, is it awesome! If you've looked at longevity before, you will be amazed at how easy it has become to start persisting your domain objects. And the best part is that everything persistence related is tucked away in the annotations. Your domain classes are completely free of persistence concerns, expressing your domain model perfectly, and ready for use in all portions of your application. Of course, we also provide a complete persistence layer for you, saving you countless hours of development effort!

See for yourself, here is a simple example demonstrating how easy it is to get started:

More API Simplifications in Longevity 0.17

Longevity is the persistence framework to use with Scala and NoSQL. Release 0.17 simplifies the user API in some very pleasant ways. Empty marker traits Persistent and Embeddable are removed. Also, KeyVal now takes a single type parameter instead of two. In brief, this will make defining the classes you want to persist so much easier and more natural, as you no longer have to extend your persistent classes with empty marker traits.

Longevity Artifacts for Scala 2.11 and 2.12

So I've finally got the longevity build set up to publish artifacts for Scala versions 2.11 and 2.12! I'm a little behind on the game, but, I've been busy ;-). Please use longevity version 0.16.1 for 2.12 artifacts. I'll be publishing artifacts for both Scala versions moving forward.

I'd like to shout out to the wonderful people at ScalaTest - Bill Venners and Chua Chee Seng - for helping me resolve an interoperability issue that made the longevity 2.12 artifacts possible. Thanks again!

Partition Keys in Longevity

I'm so excited to announce the release of longevity version 0.16.0! Longevity now supports partition keys - a key where, given a key value, we can determine the node in a distributed database where the data resides (or would reside, if it existed). This is a critical feature for NoSQL databases in a distributed context. A partition key is implemented with sharding in MongoDB, and with partitioning in Cassandra.

I'll provide a brief example of a partition key here after the jump, but to learn more about it, please take a look at the user manual.

Longevity 0.15.0 - Query Enhancements

Longevity - a persistence framework for Scala and NoSQL - is now up to version 0.15.0! The latest release focuses on query enhancements. We have added orderBy, offset, and limit clauses to our queries and query DSL.

Configuration-level Optimistic Locking with Longevity

Longevity - a persistence framework for Scala and NoSQL - has been built from day one to isolate persistence concerns behind a clear, consistent, and easy to use API. The power of this design principle is demonstrated by how easy it is for you to bring optimistic locking to your application. All you have to do is set a configuration flag.

Longevity is growing to full maturity, and most features you would expect from a persistence framework are in place. Our 0.10.0 release brings many incremental improvements - including support for controlled vocabularies. But the central feature of this release is configuration-level optimistic locking.

Longevity Getting Started Guide Now Available

I'm happy to announce that the Getting Started Guide for longevity is now available. It walks through a sample application called Simple Blogging, which uses longevity on the back end, and Akka HTTP on the front.

This guide will walk you through the basics of using longevity within a real application.

Longevity Now Has a Streamlined API!

I'm very excited to announce the 0.9.0 release of longevity, which features a whole slew of API improvements that make longevity much easier to use and understand. Here are the three most significant changes:

• Shorthands are gone
• Assocs are gone
• The API for Key and KeyVal has been reworked for significant ease-of-use improvements

I'll discuss each of these changes in more detail below.

Longevity Builds Database Integration Tests For You

Longevity - a persistence framework for Scala and NoSQL - provides a variety of tools to help you test your database application. In tests where you don't want to mock your repositories, but you want to avoid the overhead of persisting to a real database, longevity provides you with a suite of fully functional in-memory repositories. There is also a test class that you can extend to test your database queries - you basically just have to build your queries, and the base class does the rest of the work for you. Finally, longevity provides you with a test class that will exercise all the basic CRUD operations for all your repositories against a test database. In this article, we'll take a look at how we go about setting up the CRUD tests.

Longevity Now Has a Cassandra Back End

Longevity release 0.5 is out! The central focus of this release is the shiny new Cassandra back end.

Longevity is a persistence framework for Scala and NoSQL. It was originally built with a MongoDB back end, but I've always planned on supporting more kinds of databases. Longevity is mature enough at this point to add a second back end, and I chose Cassandra for a few different reasons.

Longevity: A Persistence Framework for Scala and NoSQL

Longevity is a persistence framework for Scala and NoSQL. We currently support MongoDB, with a Cassandra back end coming soon. [UPDATE: We've had a Cassandra back end for a long time now. We now have a SQLite back end as well.] After having been working on this project for over a year, I am so excited to finally share it with you! I've been working hard to put in a core set of features that would make the tool feasible for you to use in a real application. The result is our MMP release, which we just put out yesterday.