{"id":6178,"date":"2023-05-23T08:00:28","date_gmt":"2023-05-23T15:00:28","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/cosmosdb\/?p=6178"},"modified":"2023-05-23T10:25:17","modified_gmt":"2023-05-23T17:25:17","slug":"real-time-data-processing-with-new-azure-cosmos-db-change-feed-modes","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/cosmosdb\/real-time-data-processing-with-new-azure-cosmos-db-change-feed-modes\/","title":{"rendered":"Real time data processing with new Azure Cosmos DB change feed modes"},"content":{"rendered":"

The Azure Cosmos DB change feed <\/span>allows<\/span> applications <\/span>to <\/span>seamlessly <\/span>r<\/span>eact to real time changes <\/span>to data<\/span>! <\/span>It\u2019s<\/span> a persistent record of changes to items in your container in the order<\/span> they occurred.<\/span> Instead of writing complex code to query <\/span>recently<\/span> modified documents, <\/span>manually <\/span>track<\/span>\u00a0checkpointin<\/span>g<\/span>,<\/span> and handle retries for errors in processing<\/span>, <\/span>the change feed <\/span>provides<\/span> ways to manage this for you<\/span>.<\/span> The c<\/span>hange feed makes<\/span> scenarios like<\/span> triggering notifications based<\/span> on<\/span> updates to your data, real-time stream processing, and data movement <\/span>even easier!<\/span><\/span>\u00a0<\/span><\/p>\n

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Change feed modes<\/span><\/span><\/h2>\n

The change feed is available in two modes, each sharing the same core concepts with key differences. Differences include the operations captured in the feed, metadata available for each change, and the retention period of changes. Multiple applications can simultaneously read the change feed for the same container in different modes to fit the requirements of your workload.<\/span><\/p>\n

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Latest version <\/span>mode<\/span><\/span>\u00a0<\/span><\/h3>\n

If you\u2019ve used change feed before, you\u2019ve used latest version mode. Latest version mode is widely used to build reactive applications and was previously the only way to read change feed. This mode captures changes from insert and update operations. It always gives you the latest version of all items in the container. Documents aren’t available in the feed once they’re deleted, and you won\u2019t get a record of their deletion in the change feed. <\/span>\u00a0<\/span><\/p>\n

In latest version mode you can process the change feed going back to the beginning of the container. Changes will always be available in the feed if there are still items in the container. <\/span>\u00a0<\/span><\/p>\n

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New<\/span>: <\/span>All versions and <\/span>deletes<\/span> mode<\/span> (<\/span>Public <\/span>Preview)<\/span><\/span>\u00a0<\/span><\/h3>\n

All versions and deletes change feed mode solves some of the key gaps in latest version mode! Every change to items in your container appears in the change feed when using this mode- including when multiple changes to a single item occur between change feed reads and when an item is deleted. Deletes from both explicit delete operations and TTL expirations are captured. Previously, there was no way to be notified when an item expired due to TTL, even if you used the \u201csoft delete\u201d pattern. This mode gives you a full view of the state of your container without any custom logic or soft deletes.<\/span>\u00a0<\/span><\/p>\n

In order to read the change feed in all versions and deletes mode, <\/span>continuous backups<\/span><\/a> must be enabled on your Azure Cosmos DB account. The retention period of all versions and deletes change feed depends on the retention period configured for continuous backups. You can process and reprocess changes in this mode as long as the changes occurred within the retention period.<\/span>\u00a0<\/span><\/p>\n

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The change feed now serves more use cases<\/span><\/span><\/h2>\n

Regardless of the mode you read it in, the Azure Cosmos DB change feed allows for efficient processing of items that have changed in a container. Latest version mode may be the best fit for your workload in many scenarios, especially if you need to process changes from the beginning of your container. In addition to the <\/span>core use cases<\/span><\/a> for change feed, all versions and deletes mode enhances many patterns like event sourcing and data movement, as well as enables new ones like auditing.<\/span>\u00a0<\/span><\/p>\n

Some use cases that are a great fit for all versions and <\/span>deletes<\/span> mode are:<\/span><\/span>\u00a0<\/span><\/p>\n