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flyrain merged 2 commits into from
Jan 23, 2025
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docs: adapt metastores.md to Quarkus #831

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docs: adapt metastores.md to Quarkus
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74 changes: 49 additions & 25 deletions site/content/in-dev/unreleased/metastores.md
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Expand Up @@ -23,33 +23,51 @@ type: docs
weight: 700
---

This page documents important configurations for connecting to production database through [EclipseLink](https://eclipse.dev/eclipselink/).
This page documents important configurations for connecting to a production database through [EclipseLink](https://eclipse.dev/eclipselink/).

## Building Polaris with EclipseLink

Polaris distributions currently do not ship with any JDBC driver included. To build Polaris with
EclipseLink, you must specify the JDBC driver when building Polaris from sources. This is done using
Gradle's project property: `-PeclipseLinkDeps=<jdbc-driver-artifact1>,<jdbc-driver-artifact2>,...`.
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See below examples for H2 and Postgres.

## 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](https://eclipse.dev/eclipselink/documentation/2.5/solutions/testingjpa002.htm)
Configure the `polaris.persistence` section in your Polaris configuration file
(`application.properties`) as follows:

By default, `conf-file` points to the embedded resource file `META-INF/persistence.xml` in the `polaris-eclipselink` module.
```
polaris.persistence.type=eclipse-link
polaris.persistence.eclipselink.configuration-file=/path/to/persistence.xml
polaris.persistence.eclipselink.persistence-unit=polaris
```

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`
Alternatively, configuration can also be done with environment variables or system properties. Refer
to the [Quarkus Configuration Reference] for more information.

## 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.
The `configuration-file` option must point to an [EclipseLink configuration file]. This file, named
`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](https://github.com/apache/polaris/blob/main/extension/persistence/eclipselink/src/main/resources/META-INF/persistence.xml) for a complete sample for connecting to the file-based H2 database.
[Quarkus Configuration Reference]: https://quarkus.io/guides/config-reference
[EclipseLink configuration file]: https://eclipse.dev/eclipselink/documentation/2.5/solutions/testingjpa002.htm

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.

A single `persistence.xml` can describe multiple [persistence units](https://eclipse.dev/eclipselink/documentation/2.6/concepts/app_dev001.htm). 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 the `persistence-unit` option in the Polaris server configuration to easily switch between persistence units.

@flyrain flyrain Jan 23, 2025

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It'd be nice to give an example of a single file with multiple units. But it isn't a blocker to me. We can improve on it later.


### Using H2

> [!IMPORTANT] H2 is an in-memory database and is not suitable for production!

The default [persistence.xml] in Polaris is already configured for H2, but you can easily customize
your H2 configuration using the persistence unit template below:

[persistence.xml]: https://github.com/apache/polaris/blob/main/extension/persistence/eclipselink/src/main/resources/META-INF/persistence.xml

```xml
<persistence-unit name="polaris" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
Expand All @@ -71,15 +89,17 @@ Polaris creates and connects to a separate database for each realm. Specifically
</persistence-unit>
```

A single `persistence.xml` can describe multiple [persistence units](https://eclipse.dev/eclipselink/documentation/2.6/concepts/app_dev001.htm). 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:
```bash
polaris> ./gradlew --no-daemon --info -PeclipseLink=true -PeclipseLinkDeps=com.h2database:h2:2.3.232 clean shadowJar
polaris> java -jar quarkus/service/build/quarkus-app/quarkus-run.jar

```shell
./gradlew clean :polaris-quarkus-server:assemble -PeclipseLinkDeps=com.h2database:h2:2.3.232
java -Dpolaris.persistence.type=eclipse-link \
-Dpolaris.persistence.eclipselink.configuration-file=/path/to/persistence.xml \
-Dpolaris.persistence.eclipselink.persistence-unit=polaris \
-jar quarkus/server/build/quarkus-app/quarkus-run.jar
```

### Postgres
### Using Postgres

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

Expand All @@ -106,7 +126,11 @@ The following shows a sample configuration for integrating Polaris with Postgres
```

To build Polaris with the necessary Postgres dependency and start the Polaris service, run the following:
```bash
polaris> ./gradlew --no-daemon --info -PeclipseLink=true -PeclipseLinkDeps=org.postgresql:postgresql:42.7.4 clean shadowJar
polaris> java -jar quarkus/service/build/quarkus-app/quarkus-run.jar

```shell
./gradlew clean :polaris-quarkus-server:assemble -PeclipseLinkDeps=org.postgresql:postgresql:42.7.4
java -Dpolaris.persistence.type=eclipse-link \
-Dpolaris.persistence.eclipselink.configuration-file=/path/to/persistence.xml \
-Dpolaris.persistence.eclipselink.persistence-unit=polaris \
-jar quarkus/server/build/quarkus-app/quarkus-run.jar
```