druid/docs/configuration/extensions.md

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id title
extensions Extensions

Druid implements an extension system that allows for adding functionality at runtime. Extensions are commonly used to add support for deep storages (like HDFS and S3), metadata stores (like MySQL and PostgreSQL), new aggregators, new input formats, and so on.

Production clusters will generally use at least two extensions; one for deep storage and one for a metadata store. Many clusters will also use additional extensions.

Core extensions

Core extensions are maintained by Druid committers.

Name Description Docs
druid-avro-extensions Support for data in Apache Avro data format. link
druid-azure-extensions Microsoft Azure deep storage. link
druid-basic-security Support for Basic HTTP authentication and role-based access control. link
druid-bloom-filter Support for providing Bloom filters in druid queries. link
druid-datasketches Support for approximate counts and set operations with Apache DataSketches. link
druid-google-extensions Google Cloud Storage deep storage. link
druid-hdfs-storage HDFS deep storage. link
druid-histogram Approximate histograms and quantiles aggregator. Deprecated, please use the DataSketches quantiles aggregator from the druid-datasketches extension instead. link
druid-kafka-extraction-namespace Apache Kafka-based namespaced lookup. Requires namespace lookup extension. link
druid-kafka-indexing-service Supervised exactly-once Apache Kafka ingestion for the indexing service. link
druid-kinesis-indexing-service Supervised exactly-once Kinesis ingestion for the indexing service. link
druid-kerberos Kerberos authentication for druid processes. link
druid-lookups-cached-global A module for lookups providing a jvm-global eager caching for lookups. It provides JDBC and URI implementations for fetching lookup data. link
druid-lookups-cached-single Per lookup caching module to support the use cases where a lookup need to be isolated from the global pool of lookups link
druid-multi-stage-query Support for the multi-stage query architecture for Apache Druid and the multi-stage query task engine. link
druid-orc-extensions Support for data in Apache ORC data format. link
druid-parquet-extensions Support for data in Apache Parquet data format. Requires druid-avro-extensions to be loaded. link
druid-protobuf-extensions Support for data in Protobuf data format. link
druid-ranger-security Support for access control through Apache Ranger. link
druid-s3-extensions Interfacing with data in Amazon S3, and using S3 as deep storage. link
druid-ec2-extensions Interfacing with AWS EC2 for autoscaling middle managers UNDOCUMENTED
druid-aws-rds-extensions Support for AWS token based access to AWS RDS DB Cluster. link
druid-stats Statistics related module including variance and standard deviation. link
mysql-metadata-storage MySQL metadata store. link
postgresql-metadata-storage PostgreSQL metadata store. link
simple-client-sslcontext Simple SSLContext provider module to be used by Druid's internal HttpClient when talking to other Druid processes over HTTPS. link
druid-pac4j OpenID Connect authentication for druid processes. link
druid-kubernetes-extensions Druid cluster deployment on Kubernetes without Zookeeper. link

Community extensions

:::info Community extensions are not maintained by Druid committers, although we accept patches from community members using these extensions. They may not have been as extensively tested as the core extensions. :::

A number of community members have contributed their own extensions to Druid that are not packaged with the default Druid tarball. If you'd like to take on maintenance for a community extension, please post on dev@druid.apache.org to let us know!

All of these community extensions can be downloaded using pull-deps while specifying a -c coordinate option to pull org.apache.druid.extensions.contrib:{EXTENSION_NAME}:{DRUID_VERSION}.

Name Description Docs
aliyun-oss-extensions Aliyun OSS deep storage link
ambari-metrics-emitter Ambari Metrics Emitter link
druid-cassandra-storage Apache Cassandra deep storage. link
druid-cloudfiles-extensions Rackspace Cloudfiles deep storage. link
druid-compressed-bigdecimal Compressed Big Decimal Type link
druid-ddsketch Support for DDSketch approximate quantiles based on DDSketch link
druid-deltalake-extensions Support for ingesting Delta Lake tables. link
druid-distinctcount DistinctCount aggregator link
druid-iceberg-extensions Support for ingesting Iceberg tables. link
druid-redis-cache A cache implementation for Druid based on Redis. link
druid-time-min-max Min/Max aggregator for timestamp. link
sqlserver-metadata-storage Microsoft SQLServer deep storage. link
graphite-emitter Graphite metrics emitter link
statsd-emitter StatsD metrics emitter link
kafka-emitter Kafka metrics emitter link
druid-thrift-extensions Support thrift ingestion link
druid-opentsdb-emitter OpenTSDB metrics emitter link
materialized-view-selection, materialized-view-maintenance Materialized View link
druid-moving-average-query Support for Moving Average and other Aggregate Window Functions in Druid queries. link
druid-influxdb-emitter InfluxDB metrics emitter link
druid-momentsketch Support for approximate quantile queries using the momentsketch library link
druid-tdigestsketch Support for approximate sketch aggregators based on T-Digest link
gce-extensions GCE Extensions link
prometheus-emitter Exposes Druid metrics for Prometheus server collection (https://prometheus.io/) link
druid-kubernetes-overlord-extensions Support for launching tasks in k8s without Middle Managers link
druid-spectator-histogram Support for efficient approximate percentile queries link
druid-rabbit-indexing-service Support for creating and managing RabbitMQ indexing tasks link

Promoting community extensions to core extensions

Please post on dev@druid.apache.org if you'd like an extension to be promoted to core. If we see a community extension actively supported by the community, we can promote it to core based on community feedback.

For information how to create your own extension, please see here.

Loading extensions

Loading core extensions

Apache 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 common.runtime.properties 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.

:::info Druid bundles two sets of configurations: one for the quickstart and one for a clustered configuration. Make sure you are updating the correct common.runtime.properties for your setup. :::

:::info Because of licensing, the mysql-metadata-storage extension does not include the required MySQL JDBC driver. For instructions on how to install this library, see the MySQL extension page. :::

Loading community 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/*" \
  -Ddruid.extensions.directory="extensions" \
  -Ddruid.extensions.hadoopDependenciesDir="hadoop-dependencies" \
  org.apache.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 common.runtime.properties to instruct Druid to load the extension.

:::info Please make sure all the Extensions related configuration properties listed here are set correctly. :::

:::info The Maven groupId for almost every community extension is org.apache.druid.extensions.contrib. The artifactId is the name of the extension, and the version is the latest Druid stable version. :::

Loading extensions from the 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.