SPI overview#

When you implement a new Trino plugin, you implement interfaces and override methods defined by the SPI.

Plugins can provide additional Connectors, Types, Functions and Custom system access control implementation. In particular, connectors are the source of all data for queries in Trino: they back each catalog available to Trino.

Code#

The SPI source can be found in the trino-spi directory in the root of the Trino source tree.

Plugin metadata#

Each plugin identifies an entry point: an implementation of the Plugin interface. This class name is provided to Trino via the standard Java ServiceLoader interface: the classpath contains a resource file named io.trino.spi.Plugin in the META-INF/services directory. The content of this file is a single line listing the name of the plugin class:

com.example.plugin.ExamplePlugin

For a built-in plugin that is included in the Trino source code, this resource file is created whenever the pom.xml file of a plugin contains the following line:

<packaging>trino-plugin</packaging>

Plugin#

The Plugin interface is a good starting place for developers looking to understand the Trino SPI. It contains access methods to retrieve various classes that a Plugin can provide. For example, the getConnectorFactories() method is a top-level function that Trino calls to retrieve a ConnectorFactory when Trino is ready to create an instance of a connector to back a catalog. There are similar methods for Type, ParametricType, Function, SystemAccessControl, and EventListenerFactory objects.

Building plugins via Maven#

Plugins depend on the SPI from Trino:

<dependency>
    <groupId>io.trino</groupId>
    <artifactId>trino-spi</artifactId>
    <scope>provided</scope>
</dependency>

The plugin uses the Maven provided scope because Trino provides the classes from the SPI at runtime and thus the plugin should not include them in the plugin assembly.

There are a few other dependencies that are provided by Trino, including Slice and Jackson annotations. In particular, Jackson is used for serializing connector handles and thus plugins must use the annotations version provided by Trino.

All other dependencies are based on what the plugin needs for its own implementation. Plugins are loaded in a separate class loader to provide isolation and to allow plugins to use a different version of a library that Trino uses internally.

For an example pom.xml file, see the example HTTP connector in the trino-example-http directory in the root of the Trino source tree.

Deploying a custom plugin#

In order to add a custom plugin to a Trino installation, create a directory for that plugin in the Trino plugin directory and add all the necessary jars for the plugin to that directory. For example, for a plugin called my-functions, you would create a directory my-functions in the Trino plugin directory and add the relevant jars to that directory.

By default, the plugin directory is the plugin directory relative to the directory in which Trino is installed, but it is configurable using the configuration variable plugin.dir. In order for Trino to pick up the new plugin, you must restart Trino.

Plugins must be installed on all nodes in the Trino cluster (coordinator and workers).