Versioned CDN Cache Keys for Current Media Streaming
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Solution Overview
Problem
Conventional content delivery networks (CDNs) face challenges in efficiently delivering current media content during live events due to difficulties in determining whether cached segments are current or outdated, leading to substantial time and resource consumption in invalidating segments using wildcard commands.
Innovation Solution
A method involving the use of version identifiers to generate cache keys, automatically rendering older versions of segments inaccessible, thereby reducing the need for explicit invalidation operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wildcard invalidation commands are used to identify and invalidate outdated segments in CDN caches, then current media content can be delivered accurately, but substantial time and processing resources are consumed due to comparison operations across all cached segments
Solution Approach 1:
The system embeds version identifiers within segment filenames during the initial encoding and storage process. This preliminary action ensures that when invalidation is needed, the CDN infrastructure can directly filter and retrieve only the current version segments without performing exhaustive comparison operations across all cached segments, thereby significantly reducing invalidation time while maintaining delivery accuracy
Solution Approach 2:
The segment files contain self-identifying version information in their filenames, allowing caching servers to autonomously determine which segments are current without requiring external invalidation commands or comparison operations. Each segment essentially identifies itself as valid or invalid based on its filename, eliminating the need for resource-intensive wildcard invalidation processes
2Reliability
If wildcard invalidation commands are propagated to all caching servers in a CDN, then outdated segments can be identified and replaced, but substantial processing resources are consumed by comparison operations
Solution Approach 1:
By embedding version identifiers directly in segment filenames, the system enables caching servers to automatically identify current segments without requiring propagation of invalidation commands across the CDN. Each caching server independently determines segment validity through simple filename matching, dramatically reducing processing resource consumption while maintaining accurate segment versioning
Solution Approach 2:
The version identification functionality is extracted from the invalidation command process and embedded directly into the segment filenames. This separation eliminates the need for complex wildcard matching and comparison operations at caching servers, reducing processing overhead while preserving the ability to accurately identify current segments
3Reliability
If all previously generated segments of downloadables are designated as invalid and replaced with up-to-date segments during live events, then current media content is delivered, but caching servers have difficulty determining whether cached segments are current or outdated
Solution Approach 1:
The system incorporates version identifiers directly into the local structure of segment filenames themselves. This local quality enhancement allows each segment to carry its own version information, enabling caching servers to easily distinguish current from outdated segments without requiring complex global invalidation tracking or comparison operations across the entire CDN
Data Source
AI summary
In various embodiments, a caching application streams segments of a downloadable to a client device. At a first point-in-time, the caching application receives a first request for a first segment of the downloadable from the client device. The caching application computes a cache key based on a request Uniform Resource Locator included in the first request and a version identifier associated with the downloadable. The caching application determines that no segment corresponding to the cache key is stored in a cache. The caching application transmits a second request for the first segment to a different server. Upon receiving a first version of the first segment from the different server, the caching server transmits a response that includes the first version of the first segment to the client device.