Metastores

This page documents important configurations for connecting to production database through EclipseLink.

Polaris Server Configuration

Configure the metaStoreManager section in the Polaris configuration (polaris-server.yml by default) as follows:

metaStoreManager:
  type: eclipse-link
  conf-file: META-INF/persistence.xml
  persistence-unit: polaris

conf-file must point to an EclipseLink configuration file

By default, conf-file points to the embedded resource file META-INF/persistence.xml in the polaris-eclipselink module.

In order to specify a configuration file outside the classpath, follow these steps.

  1. Place persistence.xml into a jar file: jar cvf /tmp/conf.jar persistence.xml
  2. Use conf-file: /tmp/conf.jar!/persistence.xml

EclipseLink Configuration - persistence.xml

The configuration file persistence.xml is used to set up the database connection properties, which can differ depending on the type of database and its configuration.

Check out the default persistence.xml for a complete sample for connecting to the file-based H2 database.

Polaris creates and connects to a separate database for each realm. Specifically, the {realm} placeholder in jakarta.persistence.jdbc.url is substituted with the actual realm name, allowing the Polaris server to connect to different databases based on the realm.

Note: some database systems such as Postgres don’t create databases automatically. Database admins need to create them manually before running Polaris server.

<persistence-unit name="polaris" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>org.apache.polaris.core.persistence.models.ModelEntity</class>
    <class>org.apache.polaris.core.persistence.models.ModelEntityActive</class>
    <class>org.apache.polaris.core.persistence.models.ModelEntityChangeTracking</class>
    <class>org.apache.polaris.core.persistence.models.ModelEntityDropped</class>
    <class>org.apache.polaris.core.persistence.models.ModelGrantRecord</class>
    <class>org.apache.polaris.core.persistence.models.ModelPrincipalSecrets</class>
    <class>org.apache.polaris.core.persistence.models.ModelSequenceId</class>
    <shared-cache-mode>NONE</shared-cache-mode>
    <properties>
      <property name="jakarta.persistence.jdbc.url"
        value="jdbc:h2:file:tmp/polaris_test/filedb_{realm}"/>
      <property name="jakarta.persistence.jdbc.user" value="sa"/>
      <property name="jakarta.persistence.jdbc.password" value=""/>
      <property name="jakarta.persistence.schema-generation.database.action" value="create"/>
    </properties>
</persistence-unit>

A single persistence.xml can describe multiple persistence units. For example, with both a polaris-dev and polaris persistence unit defined, you could use a single persistence.xml to easily switch between development and production databases. Use persistence-unit in the Polaris server configuration to easily switch between persistence units.

To build Polaris with the necessary H2 dependency and start the Polaris service, run the following:

polaris> ./gradlew --no-daemon --info -PeclipseLink=true -PeclipseLinkDeps=com.h2database:h2:2.3.232 clean shadowJar
polaris> java -jar  polaris-service/build/libs/polaris-service-*.jar server ./polaris-server.yml

Postgres

The following shows a sample configuration for integrating Polaris with Postgres.

<persistence-unit name="polaris" transaction-type="RESOURCE_LOCAL">
  <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
  <class>org.apache.polaris.core.persistence.models.ModelEntity</class>
  <class>org.apache.polaris.core.persistence.models.ModelEntityActive</class>
  <class>org.apache.polaris.core.persistence.models.ModelEntityChangeTracking</class>
  <class>org.apache.polaris.core.persistence.models.ModelEntityDropped</class>
  <class>org.apache.polaris.core.persistence.models.ModelGrantRecord</class>
  <class>org.apache.polaris.core.persistence.models.ModelPrincipalSecrets</class>
  <class>org.apache.polaris.core.persistence.models.ModelSequenceId</class>
  <shared-cache-mode>NONE</shared-cache-mode>
  <properties>
    <property name="jakarta.persistence.jdbc.url"
              value="jdbc:postgresql://localhost:5432/{realm}"/>
    <property name="jakarta.persistence.jdbc.user" value="postgres"/>
    <property name="jakarta.persistence.jdbc.password" value="postgres"/>
    <property name="jakarta.persistence.schema-generation.database.action" value="create"/>
    <property name="eclipselink.persistence-context.flush-mode" value="auto"/>
  </properties>
</persistence-unit>

To build Polaris with the necessary Postgres dependency and start the Polaris service, run the following:

polaris> ./gradlew --no-daemon --info -PeclipseLink=true -PeclipseLinkDeps=org.postgresql:postgresql:42.7.4 clean shadowJar
polaris> java -jar  polaris-service/build/libs/polaris-service-*.jar server ./polaris-server.yml