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From "Jason Brown (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14013) Data loss in snapshots keyspace after service restart
Date Mon, 13 Nov 2017 23:04:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14013?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16250453#comment-16250453
] 

Jason Brown commented on CASSANDRA-14013:
-----------------------------------------

OK, I walked through [~kongo2002]'s example script above on the 3.11 branch, and indeed I
am able to reproduce. I tried on 3.0, and I think it did not repro (would need to do it again,
tbqh).

I don't have time to dig in for the next few days, but I suspect it's because you named the
keyspace "{{snapshots}}", and cassandra might be getting confused by trying to clean up any
data it thinks is "snapshot" data. Especially as you have other keyspaces by other names,
and you are not seeing this problem, I'm guessing we have a bug in the handling of subdirectories
names "snapshots"

> Data loss in snapshots keyspace after service restart
> -----------------------------------------------------
>
>                 Key: CASSANDRA-14013
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14013
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Gregor Uhlenheuer
>
> I am posting this bug in hope to discover the stupid mistake I am doing because I can't
imagine a reasonable answer for the behavior I see right now :-)
> In short words, I do observe data loss in a keyspace called *snapshots* after restarting
the Cassandra service. Say I do have 1000 records in a table called *snapshots.test_idx* then
after restart the table has less entries or is even empty.
> My kind of "mysterious" observation is that it happens only in a keyspace called *snapshots*...
> h3. Steps to reproduce
> These steps to reproduce show the described behavior in "most" attempts (not every single
time though).
> {code}
> # create keyspace
> CREATE KEYSPACE snapshots WITH replication = {'class': 'SimpleStrategy', 'replication_factor':
1};
> # create table
> CREATE TABLE snapshots.test_idx (key text, seqno bigint, primary key(key));
> # insert some test data
> INSERT INTO snapshots.test_idx (key,seqno) values ('key1', 1);
> ...
> INSERT INTO snapshots.test_idx (key,seqno) values ('key1000', 1000);
> # count entries
> SELECT count(*) FROM snapshots.test_idx;
> 1000
> # restart service
> kill <cassandra-pid>
> cassandra -f
> # count entries
> SELECT count(*) FROM snapshots.test_idx;
> 0
> {code}
> I hope someone can point me to the obvious mistake I am doing :-)
> This happened to me using both Cassandra 3.9 and 3.11.0



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