Dan Kinder created CASSANDRA-8892:
-------------------------------------
Summary: Read after write inconsistent even on single-node cluster
Key: CASSANDRA-8892
URL: https://issues.apache.org/jira/browse/CASSANDRA-8892
Project: Cassandra
Issue Type: Bug
Environment: Centos 6.6, Cassandra 2.0.12
Reporter: Dan Kinder
Priority: Minor
Posted on mailing list, original email:
I had been having the same problem as in those older post:
http://mail-archives.apache.org/mod_mbox/cassandra-user/201411.mbox/%3CCAORswtz+W4Eg2CoYdnEcYYxp9dARWsotaCkyvS5M7+Uo6HT1=a...@mail.gmail.com%3E
To summarize it, on my local box with just one cassandra node I can update and
then select the updated row and get an incorrect response.
My understanding is this may have to do with not having fine-grained enough
timestamp resolution, but regardless I'm wondering: is this actually a bug or
is there any way to mitigate it? It causes sporadic failures in our unit tests,
and having to Sleep() between tests isn't ideal. At least confirming it's a bug
would be nice though.
For those interested, here's a little go program that can reproduce the issue.
When I run it I typically see:
{noformat}
Expected 100 but got: 99
Expected 1000 but got: 999
{noformat}
--- main.go: ---
{code}
package main
import (
"fmt"
"github.com/gocql/gocql"
)
func main() {
cf := gocql.NewCluster("localhost")
db, _ := cf.CreateSession()
// Keyspace ut = "update test"
err := db.Query(`CREATE KEYSPACE IF NOT EXISTS ut
WITH REPLICATION = {'class': 'SimpleStrategy',
'replication_factor': 1 }`).Exec()
if err != nil {
panic(err.Error())
}
err = db.Query("CREATE TABLE IF NOT EXISTS ut.test (key text, val text,
PRIMARY KEY(key))").Exec()
if err != nil { panic(err.Error())
}
err = db.Query("TRUNCATE ut.test").Exec()
if err != nil {
panic(err.Error())
}
err = db.Query("INSERT INTO ut.test (key) VALUES ('foo')").Exec()
if err != nil {
panic(err.Error())
}
for i := 0; i < 10000; i++ {
val := fmt.Sprintf("%d", i)
db.Query("UPDATE ut.test SET val = ? WHERE key = 'foo'", val).Exec()
var result string
db.Query("SELECT val FROM ut.test WHERE key = 'foo'").Scan(&result)
if result != val {
fmt.Printf("Expected %v but got: %v\n", val, result)
}
}
}
{code}
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