Immutable Counter Ledger for Distributed Systems
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Solution Overview
Problem
Implementing counters and Last-N features in distributed systems is challenging due to the need for atomic, durable, and consistent state changes, which often requires trading off performance, scalability, reliability, and complexity.
Innovation Solution
The system uses a counter ledger with an immutable table for writing counter updates and generates snapshots from the latest counter snapshot and selected counter entries, ensuring atomicity, durability, and consistency while optimizing performance and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional distributed counter implementations are used to ensure atomicity, durability, and consistency, then reliability is improved, but performance and scalability deteriorate
Solution Approach 1:
The system segments counter operations into two distinct phases: (1) asynchronous writes to the counter ledger that do not block, and (2) periodic snapshot generations that consolidate changes. This segmentation allows high-throughput writes while maintaining periodic consistency checks, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The system performs preliminary actions by maintaining an immutable counter ledger that continuously accumulates counter updates without blocking writes. Snapshot generations are scheduled in advance and execute periodically to consolidate these preliminary changes into consistent states, ensuring reliability without impacting real-time write performance.
2Reliability
If traditional distributed counter implementations are used to ensure atomicity and consistency, then reliability is improved, but system complexity increases
Solution Approach 1:
The system creates simplified copies of counter states through snapshots that are generated periodically from the immutable ledger. These snapshots provide readable, consistent views of counter data without requiring complex distributed locking mechanisms during read operations, thereby reducing system complexity while maintaining consistency.
Solution Approach 2:
The snapshot generation process acts as an intermediary that mediates between the immutable counter ledger and application reads. It consolidates scattered counter updates into coherent snapshot states, simplifying the complexity of ensuring consistency across distributed nodes while maintaining reliability.
3Measurement precision
If frequent snapshot generations are performed to improve counter freshness, then measurement precision is improved, but processing overhead increases
Solution Approach 1:
The system implements periodic snapshot generation at configurable intervals rather than continuous or frequent snapshots. This periodic action balances counter freshness (measurement precision) with processing overhead by consolidating multiple small updates into periodic batch operations, reducing overall processing energy consumption while maintaining acceptable freshness levels.
Solution Approach 2:
Counter updates are preliminarily accumulated in the immutable ledger before snapshot generation. This preliminary accumulation allows the system to process batches of updates together during snapshot creation rather than generating snapshots after each individual update, significantly reducing processing overhead while maintaining counter freshness through periodic consolidation.
Data Source
AI summary
Systems and methods for computing counters in a distributed system are described. One embodiment includes receiving a counter update request, that includes at least one counter entry each including a timestamp, an operation value, a first set of dimension values, and at least one counter value, writing to a counter ledger, where the counter ledger comprises an immutable table where each entry has a first timestamp, an operation, a first set of dimensions, and a first at least one counter state, each counter state restricted to numeric values, reading a latest counter snapshot from an immutable snapshot ledger, generating a new counter snapshot from the latest counter snapshot and selected counter entries in the counter ledger, where the new counter snapshot includes the second set of dimension values, a second timestamp, at least one snapshot counter value, writing the new counter snapshot to the snapshot ledger.