AWS CloudFront S3 Not Serving New Versions of Files

Table of Contents#

1. Core Concepts
   • AWS CloudFront
   • Amazon S3
   • Caching in CloudFront
2. Typical Usage Scenarios
   • Static Website Hosting
   • Media Distribution
3. Reasons for Not Serving New Versions
   • Caching Policies
   • Object Versioning
   • Invalidation
4. Common Practices
   • Checking Caching Settings
   • Using Object Versioning
   • Performing Cache Invalidation
5. Best Practices
   • Configuring Appropriate Caching Policies
   • Implementing Versioning in Filenames
   • Automating Invalidation
6. Conclusion
7. FAQ
8. References

Article#

Core Concepts#

AWS CloudFront#

CloudFront is a global CDN service provided by Amazon Web Services. It has edge locations around the world where content is cached. When a user requests content, CloudFront tries to serve it from the nearest edge location, reducing latency and improving the user experience.

Amazon S3#

S3 is an object storage service that allows you to store and retrieve data from anywhere on the web. You can use S3 to host static websites, store media files, and more. CloudFront can be configured to serve content from an S3 bucket.

Caching in CloudFront#

Caching is a key feature of CloudFront. When a user requests a file, CloudFront checks if it has a cached copy at the edge location. If it does, it serves the cached file instead of fetching it from the origin (in this case, the S3 bucket). This reduces the load on the origin and speeds up content delivery. However, this can also lead to the problem of serving old versions of files if the cache is not updated.

Typical Usage Scenarios#

Static Website Hosting#

Many developers use S3 to host static websites and CloudFront to distribute the content globally. When you update the HTML, CSS, or JavaScript files in the S3 bucket, you expect the changes to be reflected immediately for all users. But if CloudFront is still serving the cached versions, users will not see the new content.

Media Distribution#

For media companies, S3 can be used to store videos, images, and audio files, and CloudFront can be used to deliver them to users. If a new version of a media file is uploaded to the S3 bucket, CloudFront may continue to serve the old version, leading to a poor user experience.

Reasons for Not Serving New Versions#

Caching Policies#

CloudFront caching policies determine how long objects are cached at the edge locations. If the caching policy is set to a long time, CloudFront will continue to serve the cached version of the file even after the file has been updated in the S3 bucket.

Object Versioning#

If object versioning is enabled in the S3 bucket, CloudFront may not automatically switch to the new version of the file. It may continue to serve the old version unless configured otherwise.

Invalidation#

If you don't perform cache invalidation, CloudFront will not update its cache. Cache invalidation is the process of telling CloudFront to remove the cached objects and fetch new ones from the origin.

Common Practices#

Checking Caching Settings#

Review the caching policies in your CloudFront distribution. You can adjust the minimum, maximum, and default TTL (Time - To - Live) values. Lowering these values will cause CloudFront to re - check the origin more frequently for updated content.

Using Object Versioning#

Enable object versioning in your S3 bucket. This allows you to manage different versions of the same object. However, you need to ensure that CloudFront is configured to handle versioned objects correctly.

Performing Cache Invalidation#

You can manually invalidate the cache for specific files or paths in your CloudFront distribution. Go to the CloudFront console, select the distribution, and choose "Invalidations". Then, enter the paths of the files you want to invalidate.

Best Practices#

Configuring Appropriate Caching Policies#

For files that change frequently, such as JavaScript and CSS files, set a lower TTL. For files that don't change often, like images, you can set a higher TTL. This way, you can balance between performance and ensuring that users get the latest content.

Implementing Versioning in Filenames#

Instead of relying solely on object versioning in S3, you can also version your filenames. For example, instead of style.css, use style-v2.css. When you update the file, you can reference the new filename in your HTML, ensuring that CloudFront serves the new version.

Automating Invalidation#

Use AWS Lambda functions or other automation tools to perform cache invalidation whenever a file is updated in the S3 bucket. This ensures that CloudFront always serves the latest content without manual intervention.

Conclusion#

The issue of AWS CloudFront not serving new versions of files from an S3 bucket can be frustrating, but it can be resolved by understanding the core concepts of CloudFront caching, S3 object versioning, and cache invalidation. By following the common practices and best practices outlined in this blog post, you can ensure that your users always receive the latest content from your S3 bucket through CloudFront.

FAQ#

1. How long does cache invalidation take in CloudFront? Cache invalidation usually takes a few minutes to complete. However, it can take up to 15 minutes in some cases.
2. Can I invalidate the entire cache in CloudFront? Yes, you can invalidate the entire cache by using the wildcard /* when creating an invalidation.
3. What happens if I don't enable object versioning in my S3 bucket? If you don't enable object versioning, you won't be able to manage different versions of the same object. When you overwrite a file in the S3 bucket, the old version is lost.

References#

• AWS CloudFront Documentation: https://docs.aws.amazon.com/cloudfront/index.html
• Amazon S3 Documentation: https://docs.aws.amazon.com/s3/index.html
• AWS Lambda Documentation: https://docs.aws.amazon.com/lambda/index.html