Forced Refresh Mechanism for CDN Cache Consistency
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Solution Overview
Problem
Content delivery networks (CDNs) face challenges in efficiently managing cache consistency and recovering from data corruption, particularly due to network issues, where it is difficult to determine which cached objects are corrupt and performing periodic revalidation of all objects can strain the network.
Innovation Solution
Implementing a forced refresh mechanism using revalidation with batch processing, where edge servers are prompted to update cached objects by changing their tags, even if they have not been updated, to ensure all cached objects are refreshed without overwhelming the network, and using a recovery module to manage this process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic revalidation of all cached objects is performed, then cache consistency is improved, but network performance deteriorates due to excessive traffic
Solution Approach 1:
The patent divides the revalidation process into batches, where only a subset of cached objects is revalidated in each time period. This segmentation approach allows the system to maintain cache consistency progressively without generating excessive network traffic that would degrade overall network performance.
2Reliability
If forced refresh of cached objects is performed, then cache consistency is improved, but network load increases
Solution Approach 1:
The patent implements forced refresh operations on a periodic basis, where cached objects are refreshed at predetermined time intervals rather than all at once. This periodic action ensures that cache consistency is maintained while distributing the network load over time, preventing overwhelming the network with simultaneous refresh requests.
3Reliability
If all cached objects are refreshed simultaneously, then cache consistency is improved, but system performance deteriorates
Solution Approach 1:
The patent segments the cached objects into multiple groups and refreshes them in successive batches rather than simultaneously. This segmentation allows the system to maintain cache consistency across all objects while preserving system performance by preventing resource exhaustion that would result from simultaneous refresh operations.
4Reliability
If revalidation is performed frequently, then cache consistency is improved, but network traffic increases
Solution Approach 1:
The patent performs revalidation on a partial basis, selecting only a subset of cached objects for revalidation in each time period rather than validating all objects frequently. This partial action approach maintains adequate cache consistency while significantly reducing the network traffic that would result from frequent comprehensive revalidation.
Data Source
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AI summary
The embodiments herein describe a CDN that uses revalidation to force edge servers to refresh their cached objects (i.e., download new copies of the objects from the origin data center). Revalidation can be used by edge servers to determine whether an object currently cached at the edge servers has been updated or changed in the origin data center. The embodiments herein leverage revalidation to perform a forced refresh to force the edge servers to refresh their cached object, regardless whether those cached objects match the objects stored in the origin data center. A forced refresh can be used when there is a network connection that may have caused the cached objects to become corrupted. Moreover, the forced refresh can be performed in batches so as not to overwhelm the network and computing resources in the CDN.