Table of Contents API documentation

Loading extensions

Loading core extensions

Druid bundles all core extensions out of the box. See the list of extensions for your options. You can load bundled extensions by adding their names to your druid.extensions.loadList property. For example, to load the postgresql-metadata-storage and druid-hdfs-storage extensions, use the configuration:

druid.extensions.loadList=["postgresql-metadata-storage", "druid-hdfs-storage"]

These extensions are located in the extensions directory of the distribution.

Druid bundles two sets of configurations: one for the quickstart and one for a clustered configuration. Make sure you are updating the correct for your setup.
Because of licensing, the mysql-metadata-storage extension is not packaged with the default Druid tarball. In order to get it, you can download it from, then unpack and move it into the extensions directory. Make sure to include the name of the extension in the loadList configuration.

Loading community and third-party extensions (contrib extensions)

You can also load community and third-party extensions not already bundled with Druid. To do this, first download the extension and then install it into your extensions directory. You can download extensions from their distributors directly, or if they are available from Maven, the included pull-deps can download them for you. To use pull-deps, specify the full Maven coordinate of the extension in the form groupId:artifactId:version. For example, for the (hypothetical) extension com.example:druid-example-extension:1.0.0, run:

java \
  -cp "lib/*" \"extensions" \
  -Ddruid.extensions.hadoopDependenciesDir="hadoop-dependencies" \
  io.druid.cli.Main tools pull-deps \
  --no-default-hadoop \
  -c "com.example:druid-example-extension:1.0.0"

You only have to install the extension once. Then, add "druid-example-extension" to druid.extensions.loadList in to instruct Druid to load the extension.

Please make sure all the Extensions related configuration properties listed here are set correctly.
The Maven groupId for almost every community extension is io.druid.extensions.contrib. The artifactId is the name of the extension, and the version is the latest Druid stable version.

Loading extensions from classpath

If you add your extension jar to the classpath at runtime, Druid will also load it into the system. This mechanism is relatively easy to reason about, but it also means that you have to ensure that all dependency jars on the classpath are compatible. That is, Druid makes no provisions while using this method to maintain class loader isolation so you must make sure that the jars on your classpath are mutually compatible.