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https://issues.apache.org/jira/browse/CASSANDRA-17473?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Brown updated CASSANDRA-17473:
------------------------------------
    Description: 
We use cassandra snapshots and {tar} to make full backups of our cassandra 
clusters. Sometimes, tar fails with a message like

{{tar: 
data/addresses/addresses-eb0196100b7d11ec852b1541747d640a/snapshots/backup20220318183708/nb-167-big-Data.db:
 file changed as we read it}}

This is kind of strange, since we're reading from a snapshot.

The (very simplified) relevant snippet looks roughly like

{{nice nodetool "${JMX_ARGS[@]}" snapshot -t "$TAG" "${KEYSPACES[@]}"}}
{{tar --hard-dereference -czpf data/*/*/snapshots/"$TAG"/}}

This happens maybe 1% of the time when taking backups.

There are no concurrent snapshots going on, but there are concurrent 
compactions and repairs, of course. If it matters, this cluster _is_ running 
incremental repairs.

This is on Cassandra 4.0.3.

It seems wrong to me that an sstable could ever be written to while it's in a 
snapshot.

  was:
We use cassandra snapshots and {tar} to make full backups of our cassandra 
clusters. Sometimes, tar fails with a message like

{{tar: 
data/addresses/addresses-eb0196100b7d11ec852b1541747d640a/snapshots/backup20220318183708/nb-167-big-Data.db:
 file changed as we read it}}

This is kind of strange, since we're reading from a snapshot.

The (very simplified) relevant snippet looks roughly like

{{nice nodetool "${JMX_ARGS[@]}" snapshot -t "$TAG" "${KEYSPACES[@]}"
tar --hard-dereference -czpf data/*/*/snapshots/"$TAG"/}}

This happens maybe 1% of the time when taking backups.

There are no concurrent snapshots going on, but there are concurrent 
compactions and repairs, of course. If it matters, this cluster _is_ running 
incremental repairs.

This is on Cassandra 4.0.3.

It seems wrong to me that an sstable could ever be written to while it's in a 
snapshot.


> sstables changing in snapshots
> ------------------------------
>
>                 Key: CASSANDRA-17473
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-17473
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: James Brown
>            Priority: Normal
>
> We use cassandra snapshots and {tar} to make full backups of our cassandra 
> clusters. Sometimes, tar fails with a message like
> {{tar: 
> data/addresses/addresses-eb0196100b7d11ec852b1541747d640a/snapshots/backup20220318183708/nb-167-big-Data.db:
>  file changed as we read it}}
> This is kind of strange, since we're reading from a snapshot.
> The (very simplified) relevant snippet looks roughly like
> {{nice nodetool "${JMX_ARGS[@]}" snapshot -t "$TAG" "${KEYSPACES[@]}"}}
> {{tar --hard-dereference -czpf data/*/*/snapshots/"$TAG"/}}
> This happens maybe 1% of the time when taking backups.
> There are no concurrent snapshots going on, but there are concurrent 
> compactions and repairs, of course. If it matters, this cluster _is_ running 
> incremental repairs.
> This is on Cassandra 4.0.3.
> It seems wrong to me that an sstable could ever be written to while it's in a 
> snapshot.



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