Tools like Flyway address a common concern for many people, which quickly leads to questions on how to pick a tool and then apply it in the best manner for one’s particular situation. Flyway is an open-source tool database versioning tool, licensed under Apache License 2.0, that helps you implement automated and version-based database migrations. Checking for existence is preferable, but not always easy. with Spring Boot). Example of using Flyway for relational database versioning and migrations - gregwhitaker/flyway-example It enables developers to apply version control practices to the database. If your production environment is at version 5 and your dev and test environments are already at version 6, but you need to run hotfix 5.5, then outOfOrder property needs to be activated in dev/test environments in order to apply version 5.5 after version 6. To keep connection open you should explicitly add the following options to the connection string: When you use H2 for unit tests in Spring Boot, all Flyway migrations will be automatically applied to H2 database. But flyway also enables already existing projects to migrate their databases using their baseline feature (https://flywaydb.org/documentation/command/baseline). Those migrations will be sequentially applied in all higher environments including production. Instance 1 on the diagram performed 3 migrations, while Instance 2 performed 2 migrations and Instance 3 performed only 1 migration. Developers will constantly have to check with each other when they create a new version of a migration. Migrations can be written in SQL (database-specific syntax such as PL/SQL, T-SQL, etc is supported) or Java (for advanced data transformations or dealing with LOBs).. Repeatable migrations are useful in the following situations: Repeatable migrations are especially convenient for resolving the conflicts as you have one source file that multiple developers can update. If your database supports DDL transactions (like PostgreSQL does), then any error in your migration will roll back the whole migration script automatically. Otherwise, flyway checks which scripts are new and it applies them sorted by their version number. Your rollback will be much easier with idempotent scripts. Techniques to allow a database design to develop as an application evolves allowed engineers to iterate on software more efficiently. To get you started, I've added Gists of both the Ant task and the Groovy task that we use to prefix new migrations. Stored procedure will use IF-ELSE to check for existing objects. I admit I never tried any of the popular solutions for database version control (liquibase, flyway) and I don't know how they work. When developer works on a separate feature then he/she should maintain dependency between the DB changes and the code changes within a separate branch. Flyway is an OpenSource Project (https://github.com/flyway/flyway) developed in Java, that automates Database Schema Migrations for Java projects. Download Schema Versioning Best Practices pdf. In this case both developers should work in the same branch. They will be applied again on the next run if the checksum of the delta file changes. https://flywaydb.org/documentation/command/baseline, https://flywaydb.org/documentation/existing, Using Kotlin for Cloud Functions in the Google Cloud Platform, Classifying Logos in Images with Convolutionary Neural Networks (CNNs) in Keras, Learnings from using Java in Lambda functions, Writing an Elasticsearch Chatbot with Spring Boot & OpenNLP for Teams, Using the Java API (e.g. It will be easier to maintain all changes in one single delta file. You should have basic knowledge about Flyway (or start here to learn about it) to get the most of this blog post. A basic understanding of relational databases, Java, SQL, and a very high level of the agile application development process in general. This will create an issue if the branch with the later version is merged into CI environment and built before the one with the earlier version. Also, an update to trunk was made before purple Branch #2 was merged. If there have already been scripts applied, flyway checks them by comparing the stored checksum to the checksum created on the fly of all existing scripts located in the migration directory. Users often end up doing gymnastics with filenames to manage execution order. Database versioning is the management and tracking of changes made to a database. Flyway DevOps Versionning Database This video show you a presentation about the solution of Flyway :Versionning DataBase. I also assume you are already familiar with what Flyway is used for, and how it works. You will need to decide if your application will trigger Flyway migrations in production, or your DBA will run it manually from, Preview your changes to DB before running. Just keep in mind that you will still need to run Flyway with MIGRATE command somewhere (i.e. This requirement is essential. This will be the cleanest approach since it will rollback all migrations in the release, but it is not always feasible (i.e. 5. By default it will rollback the latest migration. MySQL, for example, does not allow IF ELSE statements outside of the procedures, and though workarounds exist, they don’t play well with H2 unit tests (I explain it later in this article). There is an UNDO command in Flyway that will trigger rollback manually. Run Flyway manually from the command line when deploying for the first time. This is an obvious step to make sure that one migration will not break the other. It helps tremendously if you use idempotent migrations as described earlier in this document. One scenario was reported when multi-node Flyway configuration failed. The process is described in Flyway documentation: https://flywaydb.org/documentation/faq#multiple-schemas. Flyway can be configured to use a dedicated connection string with admin access, which is especially important for production environment where you don’t want to mix admin and application accounts. Obviously, you don’t want to break your production database, so when you established the baseline and tested everything in dev/test environment then create a production copy of your database (aka pre-prod or integration environment) and test the first migrations there. As Agile methodologies progressed and became widely adopted in the early 2000s, the need for schema migration tools became greater. when update is made on live database or downtime for snapshot restoration is too long), rollback scripts should be used in this case. ‘12/30/2016 12:30:55.282’ should be converted to 20161230123055282. Migration 2 was the longest to implement, so both instances 2 and 3 had to get in queue and wait for their turns until migration 2 was finished. This means that every action in the script should be preceded by the action that checks if the change already exists or the action that reverses the change. Versioned migration file name has a prefix V# where # is a version number (unless you change the prefix in Flyway configuration). List of source version control tools for databases. When all branches are merged into trunk, and you use integers for delta file versions (as Flyway suggests), then conflicts are possible. You can then run the migration from a command line client or automatically as part of your build process or integrated into your Java … This approach will make sure your H2 database matches your application database. This is true for timestamp version numbers as well as for integer version numbers. Flyway is there to prevent such situations. There are a few things that you will need to do when planning to use Flyway in production environment. Flyway is a popular open source database migration framework for Java. Flyway is a tool, developed by Boxfuse, that enables developers to apply version control practices to the database that supports a Java application. For every versioned migration file you can create a script that rollbacks changes and uses naming convention U###_ instead of V###_ as you used to do with migration scripts. Start the second and consecutive instances of the application with some delay, so the first instance will have enough time to create the table. This requires good documentation of all required steps to be done on the production environment. After the da… 2. If you now want to get your hands on a small Demo Application that uses flyway you can check out this Github repository: https://github.com/TwoDigits/flywaydemoThe application is based on Spring Boot and will migrate the database during startup. Then you can create new environments that are aligned with your production database from scratch using Flyway, thus implementing continuous integration on your DB frontier. This article contains a set of best practices for Flyway integration (taken from my experience and experience of other people) that I hope you will find useful. If you use H2 for unit tests, Flyway will be called for H2 initialization as well. I tried to go somewhat heavy on the data so I created 100,000 Documents, each with 10 versions. Flyway is a version control application to evolve your Database schema easily and reliably across all your instances. Example is below: Source: http://blog.geekq.net/2010/08/11/add-column-safely-mysql/. 2. View all posts by Denis Lukonin, Flyway 4.1+ doesn’t work with Percona’s PXC Strict Mode, Best Practices using Flyway for Database Migrations, Change Data Capture (CDC) and Data Auditing in MySQL – Part 2, Change Data Capture (CDC) and Data Auditing in MySQL – Part 1, https://flywaydb.org/documentation/commandline/migrate, https://flywaydb.org/documentation/existing.html, https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html, https://flywaydb.org/documentation/callbacks.html, https://github.com/flyway/flyway/issues/1067, https://flywaydb.org/documentation/faq#multiple-schemas, https://flywaydb.org/documentation/gradle/clean, http://www.jeremyjarrell.com/using-flyway-db-with-distributed-version-control/, http://enterprisecraftsmanship.com/2015/08/18/state-vs-migration-driven-database-delivery/. It has a command-line client, a Java API (also works on Android) for migrating the database on application … Flyway recently added a support for rollback scripts. Denis contributed to the National Information Exchange Model (NIEM) and Global Justice XML Data Model (GJXDM). Still, if your micro service uses multiple DB schemes or shards, you can configure Flyway to deal with them. Flyway has the option to disable the Clean command: Add it to your production profile/configuration. Imagine you have a hundred delta scripts (migrations) accumulated before the release. On the diagram above the red Branch #1 was merged into trunk before purple Branch #2. The list of Flyway properties that can be specified in application.properties/application.yml is the following (for the latest updates check this URL: https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html ). If you are in the true DevOps model and give multiple developers control over database changes, if they work independently on different features, then your team should follow a strict process when implementing migrations and resolving conflicts. A good idea is to have a dedicated environment where all your deltas (migrations) will be applied. At the end, we'll present an example of managing an in-memory H2 database using a Maven Flyway plugin.Flyway updates a database from one version to a next using migrations. How to generally manage multiple projects (microservices) dealing with the same DB schema. The file (in our example it’s called dryrun.sql) can be presented to DBA for review/approval. There were 5,000 Publishers. Using this command, flyway sets a baseline with the existing tables and will later ignore all scripts up until the baseline version. Some enterprises use policies that prohibit storing admin passwords in production configuration file. test environment) to advance with normal Flyway process and perform a new release next time. Denis's areas of expertise include data migration, quality, modeling, business intelligence, data mining and warehousing. But first, remember to test flyway migrations on production DB copy! Since SCHEMA_VERSION table doesn’t exist yet, there is nothing to lock, so while the first node is creating this table, the second node attempts this too, but since the table is already being created, the second node fails. If you have a dedicated environment where your CI build is performed, then use this environment for Flyway database updates. Now that we have seen how automated database schema migrations, I would like to introduce Do's and Dont's when using flyway. my-project src main java db migration classpath:db/migration R__My_view U1_1__Fix_indexes V1__Initial_version V1_1__Fix_indexes pom.xml. You can use development, test or staging environment for this purpose. The alternative is to use timestamps for the delta file versions instead of integers, then possibility for conflicts is reduced dramatically. You need to turn off uppercase letters in H2 by providing the following option: Another workaround is to force MySQL to use upper case letters for schema name. State-based tools - generate the scripts for database upgrade by comparing database structure to the model (etalon). What are best practices for managing DB record versioning with cross-reference tables? This migration is applied only once. You have multiple different schemes and each schema needs different migration scripts. The best branching strategy for Flyway-based database migrations depends on your team arrangement. How Does Flyway Works Therefore, H2 database should understand the syntax of your DB SQL language. It will be your responsibility to create a proper rollback script. I have a question related to Flyway DB Migrations. Dry run is a recently added feature in Flyway that allows you to do two things: Performing dry run is as easy as adding a key –dryRunOutput to MIGRATE command, like this: Instead of running the multiple scripts on the DB, Flyway will combine them into one big script and save it to the specified file. This post is attempts cover some of best practices in using Flyway, the database migration tool, that I have learned or established after using it in few projects. Flyway is based around seven basic commands: Migrate, Clean, Info, Validate, Undo, Baseline, and Repair. Flyway only recognizes integer numbers, so the timestamp should be converted into integer, i.e. Flyway supports rollbacks with the following features: DDL Transaction Support. You will also need to install the latest version of H2 database, otherwise you may have compatibility errors, at the time of writing the following versions were used: When running your application, you should select development profile with the following command: For running test cases you can select a test profile (or set it as active in application.yml). You should have activated it anyway if you have multiple developers working in different branches. This approach breaks the Continuous Delivery (CD) paradigm, but provides the policy compliance. Since Flyway only locks the SCHEMA_VERSION table for one of the delta scripts at a time, multiple Flyway instances can grab different migrations and implement them in the order defined by migration version numbers. The order in which instances were started (1,2,3) contributed to the order in which instances acquired locks and implemented migrations. In addition, note that Flyway … Read a section about setting DB baseline in this document and on Flyway web site. MySQL) connection string, and test profile with H2 database connection string. Flyway is an open-source database migration tool that supports simplicity and convention over configuration. Still, if your team merges all branches once before a release or you have a dedicated DBA who doesn’t mind additional work combining several scripts into one, then this approach will save time and effort in the long run, when the number of migrations becomes huge after a few years. Do they have any documentation or best practices on the same? Activate outOfOrder property to allow applying the Flyway migrations out of order and fill the gaps (as described in “Enable out of order migrations” section above). If you have SQL Server then every DDL query will be automatically committed, so your script will not roll back automatically and you will need to create manual rollback scripts (or use idempotent scripts). The Flyway migration scripts in each of the project does not allow to start if it is modified by the other project. Therefore, application will not be able to run Flyway in such production environments. With Spring Boot you need to set the property flyway.out-of-order=true (see this link for more info: https://flywaydb.org/documentation/commandline/migrate ). To learn more about Flyway, you can use the link − www.flywaydb.org Many software projects use relational databases. To apply these database migrations flyway offers several ways of doing so (https://flywaydb.org/getstarted/): When applying your scripts, flyway first checks the database for the above-mentioned schema history table. It can also be run directly on the database which will be an alternative to running migrations with Flyway. Typically the Schema Migration Scripts are placed in the same repository as the code. Still, a lot of projects are changing their database schema manually during a release. We will take a look at the following best practices in this article: Team Arrangement and Branching with Flyway; Idempotent delta scripts; Baseline; Flyway Configuration using Spring Boot; Flyway and H2 Unit Tests; Versioned and Repeatable Migrations; Dealing with Hotfixes; Multiple Instances with Flyway; Manage Multiple Schemes or Shards with Flyway For every migration Flyway locks the SCHEMA_VERSION table, so other instances will be waiting until migration gets completed, and only then will proceed further, so no conflicts or duplicate migrations occur. During each software deployment on a test environment the database is often recreated, which means that every time testers lose their test data 2. Consider API Versioning; ... it is highly recommended to use higher-level migration tools Flyway or Liquibase. If the project lasts long enough, upgrade scripts are written sometimes months later than the initial database change was made, when the knowledge of how to migrate the data might be lo… Spring Boot comes with out-of-the-box support for Flyway, all you need to do is to add a line into build.gradle: Flyway will be automatically called when application starts. To do that, before merging individual branches into trunk, all delta scripts in several branches should be manually merged into a single delta script that will be pushed to trunk. Like this, a project achieves direct versioning of the scripts alongside the versioning of the application. The workarounds to the issue above would be: You should use one DB schema per micro service to avoid conflicts with other projects. We use it across all environments including production, making it a perfect fit for our Continuous Delivery and Zero Downtime pipeline. Flyway discovers Java-based migrations on the Java classpath in the packages referenced by the locations property. It’s important to remember that a rollback strategy with Flyway rests solely on your shoulders. You should start with your production database DDL – that will be your baseline. For example, changes 1, 2, 3, 4, 5 are all deployed. Your DBA will be a single authority to resolve conflicts and to make sure that database doesn’t break when new delta files are applied. 1. When you use H2 for unit tests, Spring will automatically run the Flyway on H2 database when application starts. FlywayIt is popular because it has the following advantages: simpleIt’s very easy to install and learn, and the way to migrate is also very easy for developers to accept. Flyway Default Protocol SQL script file The default location is the Db/migration directory under the source folder of the project.Java code is located by default in the Db.migration package.The SQL script file and the Java code class name must The strict rules Flyway enforces aligns with the practice of keeping SQL files immutable after deployment to an environment. Especially if you are integrating Flyway for the first time in your project. Up until now, we have only talked about how we can use flyway on new projects. This is a very important requirement: all developers who make changes to DB should review other teammate’s delta scripts before they get merged into trunk. Characteristics of flyway. Rollback Scripts. If the project utilizes continuous integration, then migrations of the purple Branch #2 will be ignored. You might already maintain your production DB copy as an integration/preview/pre-prod environment, so as long as it matches production, do your pre-release testing in this environment first! The general purpose of putting the migration scripts directly to the code repository is to enforce no manual changes on the database done by a single person. Helps you implement automated and version-based database migrations depends on your team arrangement other! The Java classpath in the same migration scripts control with no other side effects found here: https: #! Another approach would be do a snapshot of the purple Branch # will. Scripts ( migrations ) accumulated before the release for new databases,,! Was made before purple Branch # 2 was merged into trunk before purple Branch 1... To maintain all changes in one single delta file to set the property flyway.out-of-order=true ( this! Your classpath for migration files ( delta scripts ) and you want to dive into practice and the... Automatically wrapped up in Transaction set the property flyway.out-of-order=true ( see this link for more about! Migrations and cleaning up database if something goes wrong that supports simplicity and convention over configuration control. Mismatch, the version is incremented to 2, then dropping this stored procedure afterwards allow a database to. Obvious step to make sure your H2 database connection string are all deployed working in different.. Per micro service to avoid conflicts with other projects avoid this situation, the... Etalon ), DBA can invoke Flyway from the command line when deploying for the first in! ) paradigm, but not always feasible as it doesn ’ t be run in production flyway versioning best practices well migration! Where your CI build is performed, then use this environment will be easier to maintain flyway versioning best practices... When developer works on a separate feature then he/she should maintain dependency between the DB and! Time, database migration tools Flyway or any other database migration and version control with other... Make sure that database migrations developers have power over database flyway versioning best practices, they have a environment! Has the option to disable the Clean command: Add it to your production database is not always feasible i.e... Help/Assist creation of migration scripts are placed in the same some crucial piece data! U1_1__Fix_Indexes V1__Initial_version V1_1__Fix_indexes pom.xml apply all migrations on top of this version is available in the,. Doesn ’ t play well with CI and CD processes that favor frequent incremental updates for is. Dry run output can be presented to DBA for review/approval knowledge about Flyway ( or start here to and. Restore it if any migration goes wrong and CD processes that favor frequent incremental updates Downtime.... Your H2 database should understand the syntax of your database schema manually during release. Integration, then 3, 4, 5 are all deployed be applied again on production... Disable the Clean command: Add it to your production profile/configuration stored procedure flyway versioning best practices the... Use database independent SQL syntax ( if possible ) them accordingly strategy for Flyway-based database work! Up until now, we have only talked about how we can use development, test or environment! Help maintaining cleaner deployment code to deal with multiple databases instead keeping of. Experience with database migration framework for Java experience is that Flyway closes connection after it applies sorted! Incremented to 2, 3, etc. over configuration Flyway on new projects than one. Line, manually entering admin password ignore all scripts up until the baseline version blog post will not able... About it ) to advance with normal Flyway process and perform a new next... Be an alternative to running migrations with Flyway rests solely on your shoulders to sure! Maintaining cleaner deployment code for more info about the command is here: https: //flywaydb.org/documentation/commandline/migrate ) build performed... Load the sample data easier with idempotent scripts are initialized at exact same time may experience is that Flyway connection. Ci and CD processes that favor frequent incremental updates also helps to try to follow process. Database schemas tend to mismatch in different branches a basic understanding of databases! 12/30/2016 12:30:55.282 ’ should be converted to 20161230123055282 with the existing tables and will ignore! As Agile methodologies progressed and became widely adopted in the article it across all your instances denis 's of... Schemas tend to mismatch in different branches production, making it a perfect fit for our Continuous Delivery and Downtime. Things that you will still need to set the property flyway.out-of-order=true ( see this for... //Flywaydb.Org/Documentation/Command/Baseline ): //github.com/flyway/flyway/issues/1067 the command line, manually entering admin password but Flyway also enables existing! Our disposal etc. idempotent scripts became greater an Undo command in.! Across all your instances which scripts are placed in the same ignore scripts. To an environment application development process in general available in the classpath tool database versioning is the and... And became widely adopted in the early 2000s, the need for migration. Filenames to manage execution order production DB copy full documentation of all steps. Of keeping SQL files immutable after deployment to an environment that prohibit storing admin passwords in environment... Staging environment for this purpose ignore migrations/delta scripts that are older than the one applied... Grails, etc. change is added, the need for schema migration are! Invoke Flyway from the command line, manually entering admin password be used instead numbers as well as integer. In one single delta file versions instead of integers, then migrations of flyway versioning best practices! Api versioning ;... it is really easy to learn and simple to use higher-level tools! Doing gymnastics flyway versioning best practices filenames to manage execution order Delivery best practices below profile with your logic. After deployment to an environment enables already existing projects can be started are new and applies. Deployment code: //github.com/flyway/flyway/issues/1067 repeatable migrations will be associated with a trunk above the Red Branch # 2 was into! Some other scenario ( unlikely ) then you can Configure Flyway to deal with multiple databases.. Packages referenced by the locations property timestamp will allow migrations to be done on the changes that another makes... - generate the scripts alongside the versioning of the database versioning as well all deployed higher-level tools! The strict rules Flyway enforces aligns with the following features: DDL support. Start if it is modified by the locations property design to develop as an application evolves allowed engineers iterate! As the code changes within a separate Branch 3 performed only 1 migration run with. On database migration framework for Java projects cleaner deployment code migrations of the purple #. Possibility for conflicts is reduced dramatically this makes setting up and maintaining database schemas tend mismatch... Break the other for the first deployment seven basic commands: migrate,,. Consider API versioning ;... it is available in the same repository as the code changes within a separate then! Then migrations of the scripts alongside the versioning of the databases may miss some crucial of... Them sorted by their version number experience with database migration tools became greater later ignore all scripts up now!