Consistent Hashing for Distributed DNS Cache Optimization
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Solution Overview
Problem
Distributed file systems face inefficiencies in maintaining a distributed DNS cache due to redundant storage and high network communication requirements, as each node in the cluster stores large amounts of DNS data and synchronizes caches, leading to resource consumption and communication overhead.
Innovation Solution
A consistent hash is used to associate DNS requests with a resolution node within the cluster, allowing each node to independently calculate the responsible node for DNS resolution, reducing the need for control messages and maintaining only necessary cache entries, and synchronizing changes asynchronously to minimize external DNS server lookups and cache updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each node maintains a local DNS cache with all historically resolved addresses, then DNS request resolution capability is improved, but storage resources and cache resources are consumed excessively
Solution Approach 1:
The patent divides the DNS cache into distributed segments across multiple nodes, where each node maintains only a portion of the cache rather than all entries. This is achieved through consistent hashing that maps DNS entries to specific nodes based on their hash values, allowing the cache to be segmented and distributed across the cluster.
Solution Approach 2:
The patent introduces a hashing dimension to organize DNS cache entries, transforming the traditional flat cache structure into a hash-based distributed structure. By computing hash values of DNS entries and using consistent hashing algorithms, the system creates a new dimensional organization that enables efficient distribution and reduces redundant storage.
2Stability of the object's composition
If each node synchronizes its local DNS cache with other nodes, then cache consistency is improved, but network communication resources are consumed excessively
Solution Approach 1:
The patent segments the cache synchronization process by dividing cache entries into distinct hash ranges, where each node only synchronizes its assigned segment rather than the entire cache. This reduces the amount of data that needs to be communicated between nodes during synchronization operations.
Solution Approach 2:
The patent implements preliminary actions by pre-computing and distributing cache entry assignments before actual synchronization occurs. Each node knows in advance which entries belong to it based on consistent hashing, allowing it to selectively synchronize only relevant entries rather than performing full cache synchronization.
3Speed
If DNS cache entries are stored at every node, then local resolution speed is improved, but the complexity of maintaining the distributed cache is increased
Solution Approach 1:
The patent implements self-service by enabling each node to autonomously determine its cache responsibilities through consistent hashing without requiring centralized coordination. Each node independently computes which DNS entries it should cache based on the hash of the entry and the distributed hash table, eliminating complex centralized management.
Solution Approach 2:
The patent performs preliminary actions by pre-establishing the mapping between DNS entries and responsible nodes through consistent hashing before runtime operations. This pre-computed mapping allows nodes to independently manage their cache responsibilities without complex real-time coordination, simplifying maintenance while enabling fast local resolution.
Data Source
AI summary
Implementations are provided herein for using a distributed DNS cache that is distributed among nodes of a cluster of nodes operating as a distributed file system. A consistent hash can be used to determine a resolution node for a DNS request asking to resolve a specific FQDN. The inputs to the consistent hashing algorithm can be the FQDN, a set of available nodes, and a set of all possible nodes. By using a consistent hash, the process can reduce the sensitivity of the hashing algorithm output from changing when nodes added or removed as participants in the distributed cache service. As each node in the cluster of nodes can independently calculate a resolution node for specific FQDN, there is no need to send control messages between nodes, as each node only needs to be aware of the set of available nodes in the cluster of nodes.