Redis: Diskless Replication Performance Fix
Redis merged a critical fix for diskless replication where slow replicas were causing all replicas to stall during RDB synchronization. The fix improves test reliability and prevents TCP buffer issues from blocking the entire replication process.
Duration: PT1M50S
Episode overview
This episode is a short developer briefing from Redis.
It explains recent repository work in plain language.
- Show: Redis
- Published: 2026-05-20T10:02:11Z
- Audio duration: PT1M50S
Transcript excerpt
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Good morning, this is your Redis development update for May 20th, 2026.
Vitah Lin merged a significant fix for diskless replication performance issues. Pull request 15131 addresses a critical problem where a single slow replica could stall RDB data delivery to all replicas during diskless replication. The root cause was in the RDB pipe read handler - when any replica's TCP send buffer…
The issue manifested as a burst-and-stall pattern where fast replicas would starve for 4 to 5 seconds while waiting for slow replicas to drain their buffers. This led to significantly degraded synchronization performance across the entire master-replica cluster.
The merged solution focuses on test improvements to better handle these scenarios. Key changes include skipping the diskless replica test under Valgrind to avoid timing issues, creating fresh master instances for each test subcase instead of sharing state, and optimizing dataset sizes to exercise the blocked-writer…
This change builds on previous work from Valkey issue 3511 and closes Redis issue 14983. The pull request received thorough review with 8 comments before approval, indicating the complexity and importance of this replication…
What's…
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