Apache Druid
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Getting started

  • Introduction to Apache Druid
  • Quickstart
  • Docker
  • Single server deployment
  • Clustered deployment

Tutorials

  • Loading files natively
  • Load from Apache Kafka
  • Load from Apache Hadoop
  • Querying data
  • Roll-up
  • Configuring data retention
  • Updating existing data
  • Compacting segments
  • Deleting data
  • Writing an ingestion spec
  • Transforming input data
  • Kerberized HDFS deep storage

Design

  • Design
  • Segments
  • Processes and servers
  • Deep storage
  • Metadata storage
  • ZooKeeper

Ingestion

  • Ingestion
  • Data formats
  • Schema design tips
  • Data management
  • Stream ingestion

    • Apache Kafka
    • Amazon Kinesis
    • Tranquility

    Batch ingestion

    • Native batch
    • Hadoop-based
  • Task reference
  • Troubleshooting FAQ

Querying

  • Druid SQL
  • Native queries
  • Query execution
  • Concepts

    • Datasources
    • Joins
    • Lookups
    • Multi-value dimensions
    • Multitenancy
    • Query caching
    • Context parameters

    Native query types

    • Timeseries
    • TopN
    • GroupBy
    • Scan
    • Search
    • TimeBoundary
    • SegmentMetadata
    • DatasourceMetadata

    Native query components

    • Filters
    • Granularities
    • Dimensions
    • Aggregations
    • Post-aggregations
    • Expressions
    • Having filters (groupBy)
    • Sorting and limiting (groupBy)
    • Sorting (topN)
    • String comparators
    • Virtual columns
    • Spatial filters

Configuration

  • Configuration reference
  • Extensions
  • Logging

Operations

  • Web console
  • Getting started with Apache Druid
  • Basic cluster tuning
  • API reference
  • High availability
  • Rolling updates
  • Retaining or automatically dropping data
  • Metrics
  • Alerts
  • Working with different versions of Apache Hadoop
  • HTTP compression
  • TLS support
  • Password providers
  • dump-segment tool
  • reset-cluster tool
  • insert-segment-to-db tool
  • pull-deps tool
  • Misc

    • Legacy Management UIs
    • Deep storage migration
    • Export Metadata Tool
    • Metadata Migration
    • Segment Size Optimization
    • Content for build.sbt

Development

  • Developing on Druid
  • Creating extensions
  • JavaScript functionality
  • Build from source
  • Versioning
  • Experimental features

Misc

  • Papers

Hidden

  • Apache Druid vs Elasticsearch
  • Apache Druid vs. Key/Value Stores (HBase/Cassandra/OpenTSDB)
  • Apache Druid vs Kudu
  • Apache Druid vs Redshift
  • Apache Druid vs Spark
  • Apache Druid vs SQL-on-Hadoop
  • Authentication and Authorization
  • Broker
  • Coordinator Process
  • Historical Process
  • Indexer Process
  • Indexing Service
  • MiddleManager Process
  • Overlord Process
  • Router Process
  • Peons
  • Approximate Histogram aggregators
  • Apache Avro
  • Microsoft Azure
  • Bloom Filter
  • DataSketches extension
  • DataSketches HLL Sketch module
  • DataSketches Quantiles Sketch module
  • DataSketches Theta Sketch module
  • DataSketches Tuple Sketch module
  • Basic Security
  • Kerberos
  • Cached Lookup Module
  • Apache Ranger Security
  • Google Cloud Storage
  • HDFS
  • Apache Kafka Lookups
  • Globally Cached Lookups
  • MySQL Metadata Store
  • ORC Extension
  • Druid pac4j based Security extension
  • Apache Parquet Extension
  • PostgreSQL Metadata Store
  • Protobuf
  • S3-compatible
  • Simple SSLContext Provider Module
  • Stats aggregator
  • Test Stats Aggregators
  • Ambari Metrics Emitter
  • Apache Cassandra
  • Rackspace Cloud Files
  • DistinctCount Aggregator
  • Graphite Emitter
  • InfluxDB Line Protocol Parser
  • InfluxDB Emitter
  • Kafka Emitter
  • Materialized View
  • Moment Sketches for Approximate Quantiles module
  • Moving Average Query
  • OpenTSDB Emitter
  • Druid Redis Cache
  • Microsoft SQLServer
  • StatsD Emitter
  • T-Digest Quantiles Sketch module
  • Thrift
  • Timestamp Min/Max aggregators
  • GCE Extensions
  • Aliyun OSS
  • Cardinality/HyperUnique aggregators
  • Select
  • Realtime Process
Edit

Logging

Apache Druid processes will emit logs that are useful for debugging to the console. Druid processes also emit periodic metrics about their state. For more about metrics, see Configuration. Metric logs are printed to the console by default, and can be disabled with -Ddruid.emitter.logging.logLevel=debug.

Druid uses log4j2 for logging. Logging can be configured with a log4j2.xml file. Add the path to the directory containing the log4j2.xml file (e.g. the _common/ dir) to your classpath if you want to override default Druid log configuration. Note that this directory should be earlier in the classpath than the druid jars. The easiest way to do this is to prefix the classpath with the config dir.

To enable java logging to go through log4j2, set the -Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager server parameter.

An example log4j2.xml ships with Druid under config/_common/log4j2.xml, and a sample file is also shown below:

<?xml version="1.0" encoding="UTF-8" ?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{ISO8601} %p [%t] %c - %m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="info">
      <AppenderRef ref="Console"/>
    </Root>

    <!-- Uncomment to enable logging of all HTTP requests
    <Logger name="org.apache.druid.jetty.RequestLog" additivity="false" level="DEBUG">
        <AppenderRef ref="Console"/>
    </Logger>
    -->
  </Loggers>
</Configuration>

My logs are really chatty, can I set them to asynchronously write?

Yes, using a log4j2.xml similar to the following causes some of the more chatty classes to write asynchronously:

<?xml version="1.0" encoding="UTF-8" ?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{ISO8601} %p [%t] %c - %m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <AsyncLogger name="org.apache.druid.curator.inventory.CuratorInventoryManager" level="debug" additivity="false">
      <AppenderRef ref="Console"/>
    </AsyncLogger>
    <AsyncLogger name="org.apache.druid.client.BatchServerInventoryView" level="debug" additivity="false">
      <AppenderRef ref="Console"/>
    </AsyncLogger>
    <!-- Make extra sure nobody adds logs in a bad way that can hurt performance -->
    <AsyncLogger name="org.apache.druid.client.ServerInventoryView" level="debug" additivity="false">
      <AppenderRef ref="Console"/>
    </AsyncLogger>
    <AsyncLogger name ="org.apache.druid.java.util.http.client.pool.ChannelResourceFactory" level="info" additivity="false">
      <AppenderRef ref="Console"/>
    </AsyncLogger>
    <Root level="info">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>
← ExtensionsWeb console →
  • My logs are really chatty, can I set them to asynchronously write?

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