[CASSANDRA-10021] Losing writes in a single-node cluster

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Cannot Reproduce

Environment

Docker images

• Severity: Normal
• Assignee: Sylvestor George
• Reporter: Jeremy Schlatter

Authors

Sylvestor George

• Created: 07/Aug/15 22:07
• Updated: 16/Apr/19 09:31
• Resolved: 23/Nov/15 19:49

Description

I am able to reliably reproduce write losses in the following circumstances:

• Set up a single-node cluster.
• Create keyspace with SimpleStrategy, replication_factor = 1.
• Create a table with a float field.
• Send an UPDATE command to set the float value on a row.
• After the command returns, immediately send another UPDATE to set the float value to something smaller than the first value.
• The second UPDATE is sometimes lost.

Reproduction code attached. There are two implementations: one in Go and one in C++. They do the same thing – I implemented both to rule out a bug in the client library. For both cases, you can reproduce by doing the following:

1. docker run --name repro-cassandra --rm cassandra:2.0.14
(or any other Cassandra version)
2. Download and unzip one of the zip files, and change to its directory.
3. docker build -t repro .
4. docker run --link repro-cassandra:cassandra --rm repro

The reproduction code will repeatedly run two UPDATEs followed by a SELECT until it detects a lost write, and then print:

"Lost a write. Got 20.500000, want 10.500000"

This may be fixed in 2.1.8 because I have not been able to reproduce it in that version.