We have found it very useful to set up an infrastructure where we can execute a 
nodetool command (or any other arbitrary command) from a single (non-Cassandra) 
host that will get executed on each node across the cluster (or a list of 
nodes).


Sean Durity

From: Alain RODRIGUEZ [mailto:arodr...@gmail.com]
Sent: Monday, January 15, 2018 1:19 PM
To: user cassandra.apache.org <user@cassandra.apache.org>
Subject: [EXTERNAL] Re: Even after the drop table, the data actually was not 
erased.

As you said, the auto_bootstrap setting was turned on.

Well I was talking about the 'auto_snapshot' ;-). I understand that's what you 
meant to say.

This command seems to apply only to one node. Can it be applied cluster-wide? 
Or should I run this command on each node?

Indeed, 'nodetool clearsnapshot' is only for the node where you run the 
command, like most of the nodetool commands (repair is a bit specific).

C*heers,
-----------------------
Alain Rodriguez - @arodream - 
al...@thelastpickle.com<mailto:al...@thelastpickle.com>
France / Spain

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.thelastpickle.com&d=DwMFaQ&c=MtgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=4-1G2nWjQZ3g8ZYnEhVV_NcG9TtjHJQOvqGGS1yS2KY&s=6pnDPB6ROBIPCE3CTHw-S8py99MKIG_kVcap49KKkP0&e=>

2018-01-15 1:56 GMT+00:00 Eunsu Kim 
<eunsu.bil...@gmail.com<mailto:eunsu.bil...@gmail.com>>:
Thank you for your response.  As you said, the auto_bootstrap setting was 
turned on.
The actual data was deleted with the 'nodetool clearsnapshot' command.
This command seems to apply only to one node. Can it be applied cluster-wide? 
Or should I run this command on each node?




On 12 Jan 2018, at 8:10 PM, Alain RODRIGUEZ 
<arodr...@gmail.com<mailto:arodr...@gmail.com>> wrote:

Hello,

However, the actual size of the data directory did not decrease at all. Disk 
Load monitored by JMX has been decreased.

This sounds like 'auto_snapshot' is enabled. This option will trigger a 
snapshot before any table drop / truncate to prevent user mistakes mostly. Then 
the data is removed but as it is still referenced by the snapshot (hard link), 
space cannot be freed.

Running 'nodetool clearsnapshot' should help reducing the dataset size in this 
situation.


The client fails to establish a connection and I see the following exceptions 
in the Cassandra logs.
org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find table for 
cfId…

This does not look like a failed connection to me but rather a try to query 
some inexistent data. If that's the data you just deleted (keyspace / table), 
this is expected. If not there is an other issue, I hope not related to the 
delete in this case...

C*heers,
-----------------------
Alain Rodriguez - @arodream - 
al...@thelastpickle.com<mailto:al...@thelastpickle.com>
France / Spain

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.thelastpickle.com_&d=DwMFaQ&c=MtgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=4-1G2nWjQZ3g8ZYnEhVV_NcG9TtjHJQOvqGGS1yS2KY&s=N4OglLwD-qj1p9otMAQ08CD4i88-uksigSEFHKrqmc4&e=>



2018-01-12 7:14 GMT+00:00 Eunsu Kim 
<eunsu.bil...@gmail.com<mailto:eunsu.bil...@gmail.com>>:
hi everyone

On the development server, I dropped all the tables and even keyspace dropped 
to change the table schema.
Then I created the keyspace and the table.

However, the actual size of the data directory did not decrease at all. Disk 
Load monitored by JMX has been decreased.

<Screen Shot 2018-01-12 at 3.50.22 PM.png>


After that, Cassandra does not work normally.

The client fails to establish a connection and I see the following exceptions 
in the Cassandra logs.

org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find table for 
cfId…….org.apache.cassandra.io<https://urldefense.proofpoint.com/v2/url?u=http-3A__org.apache.cassandra.io&d=DwMFaQ&c=MtgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=4-1G2nWjQZ3g8ZYnEhVV_NcG9TtjHJQOvqGGS1yS2KY&s=_R6V8rSsGURn7qbw7xM5Eo4P_mfxvXN2IcDa31iIQGU&e=>.FSReadError:
 java.io.IOException: Digest mismatch exception……


After the data is forcibly deleted, Cassandra is restarted in a clean state and 
works well.

Can anyone guess why this is happening?

Thank you in advance.




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