docs(inkless:design): add diskless-managed rf feature design #478
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Contributor
There was a problem hiding this comment.
Pull request overview
This PR adds a comprehensive design document for implementing managed replication factor (RF) for diskless topics in the Inkless system. The document proposes transitioning from the current RF=1 with faked metadata to RF=rack_count with real KRaft-managed replicas, enabling bidirectional topic migration and standard RLM integration.
Changes:
- Adds new
DISKLESS_MANAGED_RF.mddesign document with detailed approach comparison, cost analysis, and implementation plan - Updates
DESIGN.mdto reference the new design document for Stream 4: Multi-Replica Model for Diskless Topics
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| docs/inkless/ts-unification/DISKLESS_MANAGED_RF.md | New comprehensive design document proposing RF=rack_count approach with transformer-first availability, including motivation, design details, implementation path (6-8 weeks), and rejected alternatives |
| docs/inkless/ts-unification/DESIGN.md | Adds cross-references to the new DISKLESS_MANAGED_RF.md document in the Multi-Replica Model section and References section |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
ivanyu
reviewed
Jan 20, 2026
|
|
||
| | Trade-off | Accepted | Rationale | | ||
| |-----------|----------|-----------| | ||
| | KRaft metadata may show offline brokers | Yes | Availability is not blocked; eventual consistency is acceptable | |
Member
There was a problem hiding this comment.
KRaft metadata may show offline brokers
Internally or to the clients?
Contributor
Author
There was a problem hiding this comment.
To admin operations/metrics (e.g. topic describe), not to clients.
I'll clarify this
Ensure cross-az is the last resort when routing requests, and that replica placement is fully decoupled.
Contributor
Author
|
Moving it to draft to keep it as a live doc while this feature is developed. |
jeqo
added a commit
that referenced
this pull request
Jan 22, 2026
Add diskless.managed.rf.enable config (default: false) to control whether diskless topics use managed replicas with RF=rack_count or legacy RF=1. This config only affects topic creation. When enabled, new diskless topics will be created with one replica per rack using standard KRaft placement. Part of Phase 1: Diskless Managed Replicas (See #478 docs/inkless/ts-unification/DISKLESS_MANAGED_RF.md)
jeqo
added a commit
that referenced
this pull request
Jan 22, 2026
When diskless.managed.rf.enable=true, new diskless topics are created with RF=rack_count using standard KRaft replica placement instead of legacy RF=1. Changes: - Compute RF from rack cardinality via rackCardinality() - Use standard replicaPlacer.place() for rack-aware assignment - Allow manual replica assignments when managed replicas enabled - Add checkstyle suppression for extended createTopic method Phase 1 limitations: - Add Partitions inherits RF from existing partitions (Phase 3) - Transformer not updated, uses legacy routing (Phase 2) - Integration tests deferred to Phase 2 (See #478 docs/inkless/ts-unification/DISKLESS_MANAGED_RF.md)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.