Key Concepts of Azure Event Hubs
Azure Event Hubs is a highly scalable data streaming platform and event ingestion service. It can process millions of events per second. Understanding the core concepts is crucial for effectively using Event Hubs.
1. Event Hub
An Event Hub is the central entity in Azure Event Hubs. It acts as a distributed message broker that allows for ingestion and distribution of massive amounts of event data. You create an Event Hub within an Event Hubs namespace.
- It's a collection of event streams.
- Each Event Hub has configurable properties like message retention period and number of partitions.
2. Event Hubs Namespace
An Event Hubs namespace is a container for Event Hubs. A namespace provides a unique scope for Event Hubs. You can think of it as a management boundary and a logical grouping for your Event Hubs.
- Provides a unique DNS name.
- You can create multiple Event Hubs within a single namespace.
- It's also used for access control and management.
3. Event
An event is a small unit of data, typically representing a state change or an action. In Event Hubs, an event is a record of some kind. It generally contains a payload and associated metadata.
- Body: The actual data payload, typically JSON, Avro, or raw binary.
- Properties: Key-value pairs providing metadata about the event (e.g., content type, timestamp).
- Partition Key: A string property used to determine the partition to which an event is routed. Events with the same partition key are guaranteed to be routed to the same partition in the order they are sent.
4. Partition
Partitions are the fundamental unit of parallelism in Event Hubs. An Event Hub is divided into one or more partitions. Each partition is an ordered, immutable sequence of events.
- Partitions allow for parallel ingestion and consumption of events.
- The number of partitions is set at Event Hub creation and cannot be changed later.
- Events are appended to partitions.
- Consumers within a consumer group read from specific partitions.
5. Producer
A producer is any application or service that sends events to an Event Hub. Producers can send events to a specific partition or let Event Hubs choose the partition using a partition key.
- Can be any application (web app, IoT device, backend service).
- Uses Event Hubs SDKs or AMQP protocol to send events.
6. Consumer
A consumer is any application or service that reads events from an Event Hub. Consumers process events in the order they are received within a partition.
- Typically uses Event Hubs SDKs.
- Reads events from one or more partitions.
7. Consumer Group
A consumer group is an abstraction that allows multiple applications or different parts of an application to read from an Event Hub independently. Each consumer group maintains its own offset for reading events.
- Allows multiple applications to consume from the same Event Hub without interfering with each other.
- Each consumer group can independently read the entire stream of events.
- The default consumer group is named
$Default.
8. Offset
An offset is a unique, 64-bit integer identifier assigned to each event within a partition. It represents the position of an event within that partition's stream. Consumers use offsets to track their progress.
- Unique within a partition.
- Consumers commit their current offset to resume reading from where they left off.
9. Event Hubs Capture
Event Hubs Capture is a built-in feature that automatically and incrementally saves the output of an Event Hub to a Microsoft Azure Storage Blob container or Azure Data Lake Storage Gen2 account. This is useful for archival, batch processing, or replaying events.
- Configurable to save events in Avro format.
- Can be enabled on an Event Hub with a specified time or size window.
Understanding these core concepts will help you design and implement robust, scalable event-driven solutions with Azure Event Hubs.