Versioned Tuple Cache for Abortable Transactions

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Solution Overview

Problem

Storage systems face challenges in achieving atomic updates and isolation during transactions, particularly when crashes occur, as conventional redo-only logs do not allow for abortable transactions, leading to potential inconsistencies and inefficiencies.

Innovation Solution

A system utilizing a versioned tuple cache and a transaction manager that updates an in-memory key-value store with transaction identifiers, enabling opportunistic locking and low-cost transaction abortion by ignoring uncommitted transactions, and using a redo-only log for fast, abortable transactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If redo-only logs are used to achieve fast transactions, then transaction speed is improved, but transaction abortability deteriorates

Engineering Contradiction:

Improvetransaction speedVSAvoidtransaction abortability

Core Design Contradiction:

SpeedVSAdaptability or versatility

Solution Approach 1:

The patent segments the transaction log into two distinct components: a redo-only log for fast committed transactions and a versioned tuple cache for managing uncommitted transaction states. This segmentation allows the system to maintain fast committed transactions through the redo-only log while enabling abortability through the versioned tuple cache, which stores pre-image information needed for transaction rollback.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The versioned tuple cache acts as an intermediary between the redo-only log and the need for transaction abortability. It stores pre-image information (old values) of tuples before modification, allowing the system to revert changes if a transaction needs to be aborted, while the redo-only log continues to provide fast committed transaction processing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If undo-redo logs are used to achieve isolation characteristics, then isolation is improved, but overhead increases

Engineering Contradiction:

Improveisolation characteristicsVSAvoidoverhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the undo functionality from the traditional undo-redo log mechanism and places it specifically in the versioned tuple cache. This extraction allows the system to maintain isolation characteristics by storing pre-image information only when needed (for uncommitted transactions), reducing the overhead associated with maintaining undo information for all transactions throughout their entire lifecycle.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system changes the parameter of log usage by implementing a redo-only log for committed transactions, eliminating the need for undo logs for committed transactions. The versioned tuple cache maintains pre-image information dynamically based on transaction commit status, changing from a static undo-redo log approach to a dynamic, selective pre-image storage approach that reduces overhead.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10176209B2Abortable transactions using versioned tuple cache

Publication Date: 2019.01.08 VMWARE INC

AI summary

A transaction manager for handling operations on data in a storage system provides a system for executing transactions that uses a versioned tuple cache to achieve fast, abortable transactions using a redo-only log. The transaction manager updates an in-memory key-value store and also attaches a transaction identifier to the tuple as a minor key. Opportunistic locking can be accomplished due to the low cost of aborting transactions.