Cache Coherency Token for Failover in Server Clusters
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Solution Overview
Problem
In server clusters, failover events often result in cache managers being unable to manage data effectively, leading to significant processing bandwidth usage and performance degradation due to the need to reload cache data, which slows down secondary servers during failover.
Innovation Solution
The implementation of a cache module that communicates a cache coherency token to obtain permission to manage the cache and rebuilds the cache directory from stored data without reloading, allowing rapid access and minimizing performance degradation during failover events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cache data is reloaded after failover, then cache consistency is maintained, but processing bandwidth usage increases and performance degrades
Solution Approach 1:
The system performs preliminary actions by maintaining cache data in standby servers before failover events occur. The cache coherency token mechanism pre-establishes the validity state of cached data across servers, so when failover occurs, the secondary server can immediately use the existing cache without reloading, thus maintaining cache consistency while avoiding the performance penalty of data reload operations
Solution Approach 2:
The patent uses cache coherency tokens as a form of informational copy that validates cache data across multiple servers. Instead of copying actual cache data between servers, the token serves as a lightweight reference that proves the cache data's validity, allowing the secondary server to use the cache without physically reloading data, thereby reducing processing bandwidth usage while maintaining consistency
2Reliability
If cache data is reloaded after failover, then outdated cache data is avoided, but access time increases and performance slows down
Solution Approach 1:
The system performs preliminary validation by establishing cache coherency tokens before failover. These tokens pre-certify the freshness and validity of cache data, allowing the secondary server to immediately access validated cache data after failover without time-consuming reload operations, thus maintaining data freshness while minimizing access time loss
Solution Approach 2:
The cache coherency token acts as an intermediary that mediates between cache data validity and access speed. Instead of directly checking or reloading cache data to verify freshness, the system uses the token as an intermediate validation mechanism that instantly proves data freshness, allowing rapid access without sacrificing reliability
3Reliability
If cache management permission is transferred during failover, then high availability is achieved, but cache coherency must be maintained
Solution Approach 1:
Instead of copying complex cache management state or data during failover, the system copies only the essential cache coherency token information. This lightweight approach transfers cache management permission while maintaining coherency with minimal complexity, enabling high availability without the burden of complex state synchronization
Solution Approach 2:
The patent extracts the essential element of cache coherency management into a separate, manageable token structure. By separating the coherency validation logic from the main cache data and management procedures, the system simplifies the failover process - only the token needs to be transferred and validated, reducing the complexity of cache coherency management during permission transfer while maintaining high availability
Data Source
AI summary
For a high availability cache, a cache module obtains permission to manage the cache in response to a failover event in a server cluster by communicating a cache coherency token. An update module rebuilds a cache directory from data stored in the cache and accesses the cache without reloading the data stored in the cache.