Create a Storage Plugin

Create the Project

Choose a name for your project. Let's call ours "example". Storage plugins typically go in the contrib module, in a subdirectory named storage-example.

To create the project in Eclipse:

• Select the drill-contrib-parent node in the Eclipse Package Explorer.
• Choose Maven → New Maven Module Project from the context menu.
• Give your project the storage-example name.
• Accept the other defaults and create the project.
• Edit the resulting pom.xml file to add your needed dependencies. Use other storage plugins as a "cheat sheet" to see what is needed.
• Edit drill-contrib-parent/pom.xml to verify your module appears in the module list. Add it if missing:

  <modules>
    ...
    <module>storage-example</module>
    <module>data</module>
    ...
  </modules>

• (Review this part.) Get Eclipse to know about your project. Use File → Import → Existing Maven Projects. Select the Drill root. Your project should now appear in the Package Explorer as storage-example. (If this does not work, try selecting drill and Maven → Update Project.
• Eclipse named your new package org.storage.example. Rename this package to org.apache.drill.exec.store.example.
• Do the same for the test package.
• Run the Maven-provided 'App' class to ensure everything works. Select the class name, then Debug as → Java Application from the context menu.
• Delete the example App and AppTest classes.

Storage Plugin Class

The storage plugin class is Drill's main entry point to your plugin.

• Create the storage plugin class in Eclipse. The initial file should look like this:

public class SumoStoragePlugin extends AbstractStoragePlugin {
  @Override
  public StoragePluginConfig getConfig() {
    // TODO Auto-generated method stub
    return null;
  }

  @Override
  public void registerSchemas(SchemaConfig schemaConfig, SchemaPlus parent)
      throws IOException {
    // TODO Auto-generated method stub
  }
}

We'll fill in each of these as we go. We'll start with a boilerplate method that says our plugin can read data:

  @Override
  public boolean supportsRead() { return true; }

Create the plugin's config file:

• Under your src folder, create a resources subfolder.
• Select the resources folder in the Package Explorer, then, from the context menu: Build Path → Use as Source Folder.
• Under resources, create drill-module.conf (easiest to just copy from another storage plugin such as OpenTSDB):

drill.classpath.scanning: {
  packages += "org.apache.drill.exec.store.example"
}

The above tells Drill about your storage plugin.

Config Class

The config class provides all configuration information needed to execute your plugin, except the query-specific information.

• Create the ExampleStoragePluginConfig class:

@JsonTypeName(ExampleStoragePluginConfig.NAME)
public class ExampleStoragePluginConfig extends StoragePluginConfigBase {

  public static final String NAME = "example";

  public ExampleStoragePluginConfig() {
  }

  @Override
  public boolean equals(Object o) {
    return Objects.equal(null, null);
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(null, null);
  }

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        //.add("foo", foo)
        .toString();
  }

}

Add the config fields needed by your plugin. You will need:

• The field itself, which must be public and should be a simple Java type such as an int or String. (More complex types are possible, but can be tricky. Look at other config classes for examples.)
• Add either a public setFoo method or add the field to the constructor.
• Create a public getFoo method for each field.
• Add the field to the hashCode, equals and toString methods.

Add your config to the storage plugin class:

  private final ExampleStoragePluginConfig config;

  public SumoStoragePlugin(ExampleStoragePluginConfig config,
      DrillbitContext context, String name) throws IOException {
    super(context, name);
    this.config = config;
  }

  @Override
  public StoragePluginConfig getConfig() { return config; }

The constructor has special meaning to Drill: Drill uses the type of the first argument (here ExampleStoragePluginConfig ) to match a storage plugin class with a storage plugin config class.

Finally, create the default config, if any, you want for a newly-installed Drill. These defaults are also available to unit tests.

• Create the file bootstrap-storage-plugins.json in your resources folder.
• Put into the file the JSON-encoded version of your default configuration.

Or, if there is no good default, just omit this file. In this case, users will have to how to enter the JSON by hand in the Drill web console.