Upgrading to Hasura migrations config v3

What has changed?

Hasura now allows us to add multiple databases. This solves a variety of use cases. If we want to take advantage of multiple databases we’ll have to use a config v3 project which brings some changes to the project directory when compared to config v2.

Let’s try to understand what these changes are.

Metadata directory

The following is a sample metadata directory when using config v3.

metadata
├── actions.graphql
├── actions.yaml
├── allow_list.yaml
├── cron_triggers.yaml
├── databases
│   ├── databases.yaml
│   └── default
│       └── tables
│           ├── public_albums.yaml
│           ├── public_artists.yaml
├── query_collections.yaml
├── remote_schemas.yaml
└── version.yaml

Notice the introduction of a new databases directory. As the name suggests, this directory will have the metadata related to all your databases.

Now let’s looks at the contents of databases/databases.yaml

- name: default
  configuration:
    connection_info:
      database_url: <database_url>
      pool_settings:
        idle_timeout: 180
        max_connections: 50
        retries: 1
  tables:
  - "!include public_albums.yaml"
  - "!include public_artists.yaml"
  functions: []

We can see that we have a database called default, with it’s configuration information and other metadata. Take a a look at the first element under tables key. This is a special syntax/directive to hasura CLI to “include” and inline the contents of a file called public_albums.yaml. The location at which the CLI looks for this file is <project-directory>/metadata/databases/<database-name>/tables

Therefore when doing a hasura metadata apply CLI will inline elements of tables key in databases.yaml with content sourced from metadata/databases/default/tables. This allows managing metadata related a table easier since it’ll have a file of it’s own.

Currently CLI looks for !include directives in tables and functions keys only.

Migrations Directory & Seeds Directory

There are some changes to migrations and seeds project directories in config V3. Projects will have child directories corresponding to migrations for each connected database. Look at the following example, the `migrations directory has a sub directory default which corresponds to the connected database.

migrations
└── default
  └── 1613987232674_init
      └── up.sql

Changes needed in existing workflows

With the introduction of multiple databases and it’s configuration being in metadata, brings a change of workflow with it.

The steps to apply migrations and metadata to a new hasura instance will be,

# first apply metadata, this will populate hasura with configuration of connected databases
hasura metadata apply
# now we can apply migrations
hasura migrate apply --database <database-name>
# follow it with a metadata reload to make sure hasura is aware of the changes
hasura metadata reload

The reason why we have to do metadata apply first instead of migrate apply (that we are used to doing in config v2) is If we do a migrate apply first then hasura might not be aware about the databases it has to connect to. Earlier we could not start hasura without a connected database, but now we can.

Also, hasura seeds and hasura migrate now accepts a required flag --database

Upgrade steps

Step 0: Take a backup

Make sure you take a backup of your Hasura project before upgrading to config v3.

Step 1: Upgrade to the latest CLI

Run:

hasura update-cli

If you are updating to a beta/alpha release

Run:

hasura update-cli --version <version>

Step 2: Upgrade Hasura project to v3

In your project directory, run:

hasura scripts update-project-v3

Your project directory and config.yaml should be updated to v3.

The update script will ask for the name of database the current migrations and seeds correspond to. If you are starting hasura with a HASURA_GRAPHQL_DATABASE_URL then the name of the database should be default.