Distributed Session State Recovery via Hash-Based Sharding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multimedia delivery systems face challenges in dynamically resizing resources while maintaining a fully distributed mechanism for locating session state data across multiple servers, especially during changes in load demand or network resilience, which can lead to session interruptions and difficulties in restoring seamless streaming sessions.
Innovation Solution
A method for resuming Adaptive Bitrate Streaming sessions involves assigning a unique session ID to each streaming session, using a distributed policy to shard session state data across MDC instances, and employing a hash-based algorithm to determine the storage location of session state data, allowing for deterministic scaling and retrieval without a centralized mechanism, ensuring seamless session restoration across different server clusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If services are replicated across multiple servers to meet demand and provide resilience, then system reliability and load handling capability are improved, but the complexity of locating and restoring session state data across distributed servers increases
Solution Approach 1:
The system segments session state data storage by sharding it across multiple MDC instances using a hash-based distribution policy. Each session state is independently placed on specific servers based on its session ID hash, enabling parallel storage and retrieval without centralized coordination complexity.
Solution Approach 2:
The patent introduces a centralized hash map data structure as an intermediary that stores the mapping between session IDs and their corresponding MDC instances. This intermediary simplifies the distributed lookup process by allowing any MDC instance to query the hash map to determine where session state data is stored, eliminating the need for complex peer-to-peer location mechanisms.
2Adaptability or versatility
If the number of servers is dynamically resized to handle load changes, then system adaptability is improved, but the ability to maintain a fully distributed mechanism for locating session state data deteriorates
Solution Approach 1:
The system implements dynamic scalability by allowing the set of active MDC instances to change over time while maintaining the same hash-based distribution policy. When servers are added or removed, the hash map is updated to reflect the current configuration, and existing session states are redistributed if necessary. This dynamic adaptation preserves the distributed lookup mechanism without requiring reconfiguration of individual session state locations.
3Reliability
If session state data is stored across multiple servers for resilience, then system reliability is improved, but the computing resources needed for managing and retrieving session state data increase
Solution Approach 1:
The patent applies local quality by storing session state data locally on specific MDC instances rather than uniformly distributing it. The hash-based sharding policy ensures that each session state is placed on the most appropriate local server based on its session ID, reducing the need for cross-server data access and minimizing the computational overhead of retrieving and redirecting session states during failures or reconfigurations.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method for obtaining previously stored session state data for a session between a system having a plurality of nodes and a client device includes obtaining a session identifier specifying the session and hashing the session identifier. A currently valid hash map is searched. The hash map maps a hash of the session identifier to the nodes for a current system configuration. The search is performed to identify a system node on which the session state data for the session is stored. If the session state data is not located using the currently valid hash map, at least one earlier generation hash map that is valid for a previous configuration of the system is searched. Upon identifying the system node on which the session state data is stored, the session state data from the system node is retrieved. The session state data is used to establish the session.