[CASSANDRA-9059] read_repair slows down the response for mulit-dc setup with LOCAL_QUORUM read CL

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Duplicate
• Fix Version/s: 2.0.15

Environment

CentOS 6.6 , Cassandra 2.0.8

• Severity: Normal
• Since Version: 2.0.8
• Assignee: Unassigned
• Reporter: Wei Zhu
• Created: 27/Mar/15 19:10
• Updated: 16/Apr/19 09:31
• Resolved: 27/Mar/15 19:34

Description

We have two DC setup for the Cassandra Cluster. 7 nodes each, RF = 3. We setup CL as LOCAL_QUORUM for both read and write.
We have noticed that 95th percentile coordiantorReadLatency is at 60ms range.
We modified read_repair_chance for this CF to 0.0 from the default 0.1, we see dramatic improvements for the coordiantorReadLatency. It went down to 10ms.
I suspect read_repair somehow waits/blocks the response from other DC which shouldn't happen.

Issue Links

• duplicates: CASSANDRA-7902 Introduce the ability to ignore RR based on consistency