Azure Cosmos DB change feed concepts in NoSQL API

on

Change feed in Azure Cosmos DB allows you to listen to the changes happening in the order that they occur. 

Cosmos Change feed is default enabled when you create a new container.

Cosmos DB Change Feed
Cosmos DB Change Feed


For example, consider the below scenario,

When records a, b, and c are inserted, the change feed captures and processes them sequentially in the exact same order (i.e. a, b and c).

To understand more, check out below video,


We can connect using the below client drivers to extract the change feed in Azure Cosmos DB NoSQL API.

.NET
Java
Python
JavaScript / Node.js

How this change feed works?

The Cosmos DB data is distributed across several partitions physically and logically. When this change feed is enabled, it will check the feed across several partition key ranges thus allowing us to extract the feed data parallelly from a single container.

In Cosmos DB Change Feed, partition key ranges map to physical partitions when using the change feed processor and Feed Ranges when using the pull model.

Features of Cosmos DB Change feed

  1. Change feed is enabled by default for all Cosmos DB accounts.
  2. Multiple modes are available, some requiring extra configuration.
  3. You can consume change feed using provisioned throughput in any account region.
  4. It tracks insert and update operations, with optional support for deletes and TTL expirations.
  5. Each change appears exactly once, requiring clients to handle checkpointing manually.
  6. The change feed processor handles automatic checkpointing with "at least once" delivery.
  7. Changes can be processed in parallel across partition key ranges.
  8. Multiple change feed instances can be requested concurrently on the same container.
  9. The starting position for change feed is customizable, depending on the mode used.

Change Feed Modes

There are two modes available to extract the change feed currently from Azure Cosmos DB.
  1. latest version mode 
  2. all versions and deletes mode. (preview)
Latest version mode gives you the latest insert or updated records in the cosmos db container.

All versions and deletes mode allow you to get a record of each change to items in the order that it occurred, including intermediate changes to an item between change feed reads.

Work with change feed in Cosmos DB

To work with change feed, currently you have three ways.

Read Microsoft Docs on Change Feed


Change feed processors


Comments

Post a Comment