Apache Druid is an open-source, high-performance, real-time analytics database designed for fast slice-and-dice analytics on large datasets. It is well-suited for applications requiring low-latency queries on large amounts of data, such as business intelligence, operations, and monitoring.
Key Features
- Real-Time and Batch Data Ingestion: Supports both real-time streaming data and batch data ingestion from various sources.
- Column-Oriented Storage: Efficient storage format that allows for rapid access and high compression ratios.
- Time-Based Partitioning: Data is partitioned based on time, enabling fast time-based queries and data retention management.
- Distributed Architecture: Scalability and fault-tolerance through a distributed, microservices-based architecture.
Architecture Components
Data Servers:
- Historical Nodes: Store immutable segments of data and handle batch ingestion.
- Real-Time Nodes (MiddleManagers): Ingest and query real-time data.
Query Servers:
- Brokers: Distribute query requests to appropriate data servers and aggregate results.
- Coordinator: Manages data distribution and balancing across the cluster.
Data Management:
- Overlord: Coordinates data ingestion tasks.
- Metadata Storage: Stores the metadata about data segments and tasks.
Data Ingestion
Druid supports multiple ways to ingest data:
- Real-Time Ingestion: Data is ingested from streaming sources like Apache Kafka or Amazon Kinesis.
- Batch Ingestion: Data is loaded from static files stored in HDFS, Amazon S3, or other similar storage systems.
- Indexing Service: MiddleManager nodes run indexing tasks to create segments from raw data.
Querying
Druid supports a variety of query types:
- Time Series: Aggregations over time intervals.
- TopN: Finds the top N values for a given dimension.
- GroupBy: Groups data by one or more dimensions and applies aggregations.
- Search: Searches for specific string values.
- Scan: Retrieves raw data, similar to SQL
SELECT
statements.
Performance
- Segment Caching: Historical nodes cache segments to reduce query latency.
- Roll-Up: Pre-aggregates data during ingestion to reduce storage and speed up queries.
- Indexing: Bitmap and compressed indexes for efficient filtering and retrieval.
Use Cases
- Business Intelligence: Real-time dashboards and reporting.
- Operational Analytics: Monitoring and analyzing operational metrics.
- Clickstream Analytics: Analyzing web and mobile user behavior.
- Network Performance Monitoring: Tracking and analyzing network performance data.
Integrations
Apache Druid integrates with various tools and platforms:
- Data Ingestion: Apache Kafka, Amazon Kinesis, HDFS, Amazon S3.
- Querying and Visualization: Apache Superset, Tableau, Grafana.
- Data Processing: Apache Hadoop, Apache Spark, Apache Flink.
Advantages
- Scalability: Easily scales horizontally to handle increasing data volumes.
- Flexibility: Supports both real-time and batch data, accommodating various data ingestion needs.
- Performance: Optimized for fast querying and high throughput.