Server Resource Locking via Sequence Numbers and Provisional Bits

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Solution Overview

Problem

Existing distributed network systems face inefficiencies due to constant communication between servers and global locking services, which consume bandwidth and require persistent state management, leading to high loads and additional expenses.

Innovation Solution

A server system that uses a resource table with sequence numbers and provisional bits to manage lock access without persistent state, allowing provisional rejections and sequence number updates to verify lock validity, reducing direct communication with the global locking service.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If constant communication between server and global locking service is implemented, then lock validation reliability is improved, but bandwidth consumption increases and system load increases

Engineering Contradiction:

Improvelock validation reliabilityVSAvoidbandwidth consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The server performs preliminary validation by checking sequence numbers against stored snapshots before contacting the locking service. This preliminary action filters out obviously invalid requests, reducing the need for constant communication with the locking service while maintaining validation reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Sequence numbers and snapshots act as intermediaries between the server and locking service. Instead of direct constant communication, the server uses these intermediaries to validate locks locally, reducing communication overhead while maintaining reliability through periodic verification with the locking service.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If constant communication between server and global locking service is implemented, then lock validation reliability is improved, but system load on locking service increases

Engineering Contradiction:

Improvelock validation reliabilityVSAvoidsystem load

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The server performs self-validation using stored snapshots and sequence numbers, reducing dependency on the locking service. This self-service approach allows the server to independently validate most lock requests, significantly reducing the load on the locking service while maintaining reliability through periodic verification.

Inventive Principle:

Principle #25Self-service

3Loss of energy

If persistent state is stored to avoid contacting locking service on restart, then communication overhead is reduced, but memory requirements increase and system complexity increases

Engineering Contradiction:

Improvecommunication overheadVSAvoidsystem complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The server uses volatile memory for storing snapshots instead of persistent storage. These snapshots are discarded when the server restarts and automatically re-synchronized from the locking service. This approach avoids the complexity of persistent state management while keeping communication overhead low during normal operation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The system changes the state persistence parameter from persistent (non-volatile) to transient (volatile). By accepting that snapshots will be lost on restart and automatically re-synchronizing, the system simplifies memory management and reduces complexity while maintaining low communication overhead during operational periods.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If clock synchronization is implemented for lease-based locking, then lock management reliability is improved, but communication overhead increases and clock skew issues persist

Engineering Contradiction:

Improvelock management reliabilityVSAvoidcommunication overhead

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system replaces the mechanical clock synchronization mechanism with a logical sequence number system. Instead of relying on synchronized clocks and time-based leases, the server uses monotonically increasing sequence numbers from the locking service to validate locks. This substitution eliminates clock skew issues and reduces communication overhead for time synchronization.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8200774B1System and method for resource locking

Publication Date: 2012.06.12 GOOGLE LLC

AI summary

A server system includes a processor and a data structure having an entry for a resource, the entry including a first sequence number. The server has communication procedures for receiving a request from a client to access the resource, where the request includes a second sequence number obtained from a service, and a resource request handling program. Upon receiving the request, the resource request handling program determines whether the server has any record of having previously received a request to access the resource. If not, the server returns a provisional rejection to the client, requiring the client to verify that it holds a lock on the specified resource. A provisional bit in the entry is initially set to indicate that the resource has not been accessed since the system was last initialized. The provisional bit is reset when a request to access the resource is granted.