google-nomulus/db

Summary

This project contains Nomulus's Cloud SQL schema and schema-deployment utilities.

Database Roles and Privileges

Nomulus uses the 'postgres' database in the 'public' schema. The following users/roles are defined:

• postgres: the initial user is used for admin and schema deployment.
  • In Cloud SQL, we do not control superusers. The initial 'postgres' user is a regular user with create-role/create-db privileges. Therefore, it is not possible to separate admin user and schema-deployment user.
• readwrite is a role with read-write privileges on all data tables and sequences. However, it does not have write access to admin tables. Nor can it create new tables.
  • The Registry server user is granted this role.
• readonly is a role with SELECT privileges on all tables.
  • Reporting job user and individual human readers may be granted this role.

Schema DDL Scripts

Currently we use Flyway for schema deployment. Versioned incremental update scripts are organized in the src/main/resources/sql/flyway folder. A Flyway 'migration' task examines the target database instance, and makes sure that only changes not yet deployed are pushed.

Below are the steps to submit a schema change:

1. Make your changes to entity classes, remembering to add new ones to core/src/main/resources/META-INF/persistence.xml so they'll be picked up.

2. Run the nomulus generate_sql_schema command to generate a new version of db-schema.sql.generated. The full command line to do this is:

   ./gradlew devTool --args="-e localhost generate_sql_schema --start_postgresql -o /path/to/nomulus/db/src/main/resources/sql/schema/db-schema.sql.generated"

3. Write an incremental DDL script that changes the existing schema to your new one. The generated SQL file from the previous step should help. New create table statements can be used as is, whereas alter table statements should be written to change any existing tables.

   This script should be stored in a new file in the db/src/main/resources/sql/flyway folder using the naming pattern V{id}__{description text}.sql, where {id} is the next highest number following the existing scripts in that folder. Note the double underscore in the naming pattern.

4. Run the :db:test task from the Gradle root project. The SchemaTest will fail because the new schema does not match the golden file.

5. Copy db/build/resources/test/testcontainer/mount/dump.txt to the golden file db/src/main/resources/sql/schema/nomulus.golden.sql. Diff it against the old version and verify that all changes are expected.

6. Re-run the :db:test task. This time all tests should pass.

Relevant files (under db/src/main/resources/sql/schema/):

• nomulus.golden.sql is the schema dump (pg_dump for postgres) of the final schema pushed by Flyway. This is mostly for informational, although it may be used in tests.
• db-schema.sql.generated is the schema generated from ORM classes by the GenerateSqlSchema command in Nomulus tool. This reflects the ORM-layer's view of the schema.

The generated schema and the golden one may diverge during schema changes. For example, when adding a new column to a table, we would deploy the change before adding it to the relevant ORM class. Therefore, for a short time the golden file will contain the new column while the generated one does not.

Schema Push

Currently Cloud SQL schema is released with the Nomulus server, and shares the server release's tag (e.g., nomulus-20191101-RC00). Automatic schema push process (to apply new changes in a released schema to the databases) has not been set up yet, and new schema may be pushed manually on demand.

Presubmit and continuous-integration tests are being implemented to ensure server/schema compatibility. Before the tests are activated, please look for breaking changes before deploying a schema.

Released schema may be deployed using Cloud Build. Use the root project directory as working directory, run the following shell snippets:

# Tags exist as folder names under gs://domain-registry-dev-deploy.
SCHEMA_TAG=
# Recognized environments are alpha, crash, sandbox and production
SQL_ENV=
# Deploy on cloud build. The --project is optional if domain-registry-dev
# is already your default project.
gcloud builds submit --config=release/cloudbuild-schema-deploy.yaml \
    --substitutions=TAG_NAME=${SCHEMA_TAG},_ENV=${SQL_ENV} \
    --project domain-registry-dev
# Verify by checking Flyway Schema History:
./gradlew :db:flywayInfo -PdbServer=${SQL_ENV}

Glass Breaking

If you need to deploy a schema off-cycle, try making a release first, then deploy that release schema to Cloud SQL.

TODO(weiminyu): elaborate on different ways to push schema without a full release.

Notes On Flyway

Please note: to run Flyway commands, you need Cloud SDK and need to log in once.

# One time login
gcloud auth login

The Flyway-based Cloud Build schema push process is safe in common scenarios:

• Repeatedly deploying the latest schema is safe. All duplicate runs become NOP.

• Accidentally deploying a past schema is safe. Flyway will not undo incremental changes not reflected in the deployed schema.

• Concurrent deployment runs are safe. Flyway locks its own metadata table, serializing deployment runs without affecting normal accesses.

Schema Push to Local Database

The Flyway tasks may also be used to deploy to local instances, e.g, your own test instance. E.g.,

# Deploy to a local instance at standard port as the super user.
gradlew :db:flywayMigrate -PdbServer=192.168.9.2 -PdbPassword=domain-registry

# Full specification of all parameters
gradlew :db:flywayMigrate -PdbServer=192.168.9.2:5432 -PdbUser=postgres \
    -PdbPassword=domain-registry