Specify TTL for a document

Microsoft Azure Cosmos DB is a powerful NoSQL database service that provides global distribution and automatic scalability. It allows developers to build native applications that can deliver low-latency and high-throughput access to data. In this article, we will explore how to design and implement native applications using Azure Cosmos DB, focusing specifically on specifying the TTL (time to live) for a document.

Understanding TTL in Azure Cosmos DB

TTL allows you to automatically remove documents from a collection after a specific period of time. This feature is especially useful when dealing with temporary or time-sensitive data, such as session information, logs, or cache data. By setting an appropriate TTL for your documents, you can ensure efficient data management without the need for manual cleanup operations.

Specifying TTL for a Document

To specify the TTL for a document in Azure Cosmos DB, you need to define the “ttl” property in the document itself. The “ttl” property represents the time to live value in seconds. When the TTL value expires, the document will be automatically removed from the collection.

Let’s dive into an example to see how this works. Consider a scenario where you have a collection named “logs” that stores log entries for an application. Each log entry document has properties like “logId,” “message,” and “timestamp.” To specify a TTL for these log entries, you can add a “ttl” property to each document with the desired TTL value.

Here’s an example document with a TTL of 7 days (604,800 seconds):

{
"logId": "123456",
"message": "An error occurred",
"timestamp": "2022-01-01T12:34:56Z",
"ttl": 604800
}

By setting the TTL value in this way, Azure Cosmos DB will automatically remove this document from the collection after 7 days.

It’s important to note that once the TTL is set for a document, it cannot be updated. If you need to change the TTL, you will need to create a new document with the updated TTL value and delete the old document manually.

Enabling TTL for a Collection

To enable TTL for a collection in Azure Cosmos DB, you can do so during the collection creation or update process. You can specify the default TTL value for the collection, which will be applied to all documents in the collection that don’t have their own TTL values explicitly set. Additionally, you can override the default TTL for individual documents by setting the “ttl” property as we discussed earlier.

Here’s an example of enabling TTL for a collection with a default TTL of 30 days (2,592,000 seconds):

{
"id": "logs",
"indexingPolicy": {
// indexing policy configuration
},
"defaultTtl": 2592000
}

With the default TTL set, any document created within the collection will be automatically removed after 30 days unless their own TTL values are explicitly set.

Summary

Specifying the TTL for a document in Azure Cosmos DB is a powerful feature that allows you to automate data cleanup and management in your application. By defining the “ttl” property in each document or setting a default TTL for the collection, you can ensure that outdated or time-sensitive data is automatically removed without manual intervention.

Remember to refer to the official Microsoft documentation for more detailed information and guidance on how to design and implement native applications using Azure Cosmos DB and TTL settings.