RE: Restoring snapshot

[Vishal1.Sharma]

On altering the Keyspace, the warning disappears. I think the warning was not 
totally wrong, just slightly inaccurate.


From: Nitan Kainth [mailto:nitankai...@gmail.com]
Sent: Wednesday, June 13, 2018 4:38 PM
To: user@cassandra.apache.org
Subject: Re: Restoring snapshot

Change RF fir k2 and then see.
Sent from my iPhone

On Jun 13, 2018, at 7:05 AM, 
mailto:vishal1.sha...@ril.com>> 
mailto:vishal1.sha...@ril.com>> wrote:
For both K1 and K2, replication factor is 2 in the new cluster(although the 
number of nodes is 1). I can understand the portion of the warning which says 
that “only 1 replica could be found” but the question is, why is it giving the 
name of keyspace K2 when I was restoring only K1(It should have given warning 
for K1).

From: Nitan Kainth [mailto:nitankai...@gmail.com]
Sent: Wednesday, June 13, 2018 4:31 PM
To: user@cassandra.apache.org
Subject: Re: Restoring snapshot

Verify dc name and replication factor in create keyspace command in new cluster.
Sent from my iPhone

On Jun 13, 2018, at 2:40 AM, 
mailto:vishal1.sha...@ril.com>> 
mailto:vishal1.sha...@ril.com>> wrote:
Dear Community,

I took a snapshot from a node which was part of a 2 node cluster. There were 2 
keyspaces in that cluster K1 and K2. I took snapshot of K1 only. Now I create 
both keyspaces in some other cluster having only one node. When I tried to 
restore the snapshot(of keyspace K1) in that cluster using sstableloader, I got 
a warning:

“WARN  11:55:48,921 Error while computing token map for keyspace K2 with 
datacenter dc1: could not achieve replication factor 2 (found 1 replicas only), 
check your keyspace replication settings.”

Like I’ve said above, the new cluster contains only one node, therefore I can 
understand the portion of the warning telling me that ‘it only found 1 replicas 
only’, but why is it computing token map for keyspace K2 when I was restoring 
sstables of keyspace K1? Also, the same warning(regarding only K2) is displayed 
whether I try to restore snapshot of K1 or K2.  Although, I’m able to get the 
complete data, but I would appreciate if someone can explain this observations.

Cassandra version: 3.11.2

Thanks and regards,
Vishal Sharma

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RE: Restoring snapshot

[Vishal1.Sharma]

For both K1 and K2, replication factor is 2 in the new cluster(although the 
number of nodes is 1). I can understand the portion of the warning which says 
that “only 1 replica could be found” but the question is, why is it giving the 
name of keyspace K2 when I was restoring only K1(It should have given warning 
for K1).

From: Nitan Kainth [mailto:nitankai...@gmail.com]
Sent: Wednesday, June 13, 2018 4:31 PM
To: user@cassandra.apache.org
Subject: Re: Restoring snapshot

Verify dc name and replication factor in create keyspace command in new cluster.
Sent from my iPhone

On Jun 13, 2018, at 2:40 AM, 
mailto:vishal1.sha...@ril.com>> 
mailto:vishal1.sha...@ril.com>> wrote:
Dear Community,

I took a snapshot from a node which was part of a 2 node cluster. There were 2 
keyspaces in that cluster K1 and K2. I took snapshot of K1 only. Now I create 
both keyspaces in some other cluster having only one node. When I tried to 
restore the snapshot(of keyspace K1) in that cluster using sstableloader, I got 
a warning:

“WARN  11:55:48,921 Error while computing token map for keyspace K2 with 
datacenter dc1: could not achieve replication factor 2 (found 1 replicas only), 
check your keyspace replication settings.”

Like I’ve said above, the new cluster contains only one node, therefore I can 
understand the portion of the warning telling me that ‘it only found 1 replicas 
only’, but why is it computing token map for keyspace K2 when I was restoring 
sstables of keyspace K1? Also, the same warning(regarding only K2) is displayed 
whether I try to restore snapshot of K1 or K2.  Although, I’m able to get the 
complete data, but I would appreciate if someone can explain this observations.

Cassandra version: 3.11.2

Thanks and regards,
Vishal Sharma

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Restoring snapshot

[Vishal1.Sharma]

Dear Community,

I took a snapshot from a node which was part of a 2 node cluster. There were 2 
keyspaces in that cluster K1 and K2. I took snapshot of K1 only. Now I create 
both keyspaces in some other cluster having only one node. When I tried to 
restore the snapshot(of keyspace K1) in that cluster using sstableloader, I got 
a warning:

“WARN  11:55:48,921 Error while computing token map for keyspace K2 with 
datacenter dc1: could not achieve replication factor 2 (found 1 replicas only), 
check your keyspace replication settings.”

Like I’ve said above, the new cluster contains only one node, therefore I can 
understand the portion of the warning telling me that ‘it only found 1 replicas 
only’, but why is it computing token map for keyspace K2 when I was restoring 
sstables of keyspace K1? Also, the same warning(regarding only K2) is displayed 
whether I try to restore snapshot of K1 or K2.  Although, I’m able to get the 
complete data, but I would appreciate if someone can explain this observations.

Cassandra version: 3.11.2

Thanks and regards,
Vishal Sharma
"Confidentiality Warning: This message and any attachments are intended only 
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Restoring snapshot

[Vishal1.Sharma]

Dear Community,

I’ll appreciate if I can get some responses to the observation below:

https://stackoverflow.com/q/50763067/5701173

Thanks and regards,
Vishal Sharma
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Scaling in Cassandra

[Vishal1.Sharma]

Dear Community,

I’ll appreciate if I can get some help below:

https://stackoverflow.com/q/50581473/5701173

Regards,
Vishal Sharma
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RE: Database not getting updated

[Vishal1.Sharma]

Who’s awesome?

Jeff Jirsa is awesome!

☺

Thanks and regards,
Vishal Sharma

From: Jeff Jirsa [mailto:jji...@gmail.com]
Sent: Friday, May 11, 2018 5:51 PM
To: user@cassandra.apache.org
Subject: Re: Database not getting updated

This usually happens when you’ve got weird timestamps or a delete in the future 
- check your clocks, make sure your timestamp resolution uses the same units in 
all applications (likely microseconds), make sure you’re running NTP everywhere
--
Jeff Jirsa


On May 11, 2018, at 5:37 PM, 
> 
> wrote:
Dear community,

Sometimes I’ve noticed that the changes done in the database, even when done 
successfully are not reflected e.g. I added/deleted a row via cqlsh/Datastax 
C++ driver, the command/API was successful, yet when I fetched the contents of 
the table, the row that I had added/deleted, was missing/still present. Has 
anybody, noticed something similar before?
I’ve had this observation on the latest 3.11.2(earlier I had observed this on 
3.0.14). There were 2 nodes in my cluster, replication factor was 2 and 
read/write consistency was also 2.

Thanks and regards,
Vishal Sharma

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Database not getting updated

[Vishal1.Sharma]

Dear community,

Sometimes I've noticed that the changes done in the database, even when done 
successfully are not reflected e.g. I added/deleted a row via cqlsh/Datastax 
C++ driver, the command/API was successful, yet when I fetched the contents of 
the table, the row that I had added/deleted, was missing/still present. Has 
anybody, noticed something similar before?
I've had this observation on the latest 3.11.2(earlier I had observed this on 
3.0.14). There were 2 nodes in my cluster, replication factor was 2 and 
read/write consistency was also 2.

Thanks and regards,
Vishal Sharma
"Confidentiality Warning: This message and any attachments are intended only 
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are confidential and may be privileged. If you are not the intended recipient. 
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use of this message and any attachments is 
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Running multiple instances of Cassandra on each node in the cluster

[Vishal1.Sharma]

Dear community,

Is it possible to have a cluster in Cassandra where each of the server is 
running multiple instances of Cassandra(each instance is part of the same 
cluster).

I'm aware that if there's a single server in the cluster, then it's possible to 
run multiple instances of Cassandra on 
it, but is it also possible to 
have multiple such servers in the cluster. If yes, how will the configuration 
look like(listen address, ports etc)?

Even if it was possible, I understand that there might not be any performance 
benefits at all, just wanted to know if it's theoretically possible.



Stack Overflow Link: 
https://stackoverflow.com/questions/50267683/multiple-instances-of-cassandra-on-each-node-in-the-cluster



Thanks and regards,

Vishal Sharma
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Basic Copy vs Snapshot for backup

[Vishal1.Sharma]

Dear Community,

Is there any benefit of taking backup of a node via 'nodetool snapshot' vs 
simply copying the data directory other than the fact that snapshot will first 
flush the memTable and then take the backup.

Thanks and regards,
Vishal Sharma
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Integrating Apache Cassandra and Apache Ignite

[Vishal1.Sharma]

I'm trying to integrate Apache Ignite with Apache Cassandra(3.11.2) as I want 
to use Ignite to cache the data present in my already existing Cassandra 
database.
After going through the online resources, I've done the following till now:
1.  Downloaded Apache Ignite.
2.  Copied all the folders present in "libs/optional/" to "libs/"(I don't 
know which ones will be required for Cassandra).
3.  Created 3 xmls in the config folder i.e. "cassandra-config.xml", 
"connection-settings.xml" and "persistance-settings.xml". Currently I'm using 
the same node(172.16.129.68) for both Cassandra and Ignite. Please find 
attached the xml files.

4.  I run the following command to start Ignite from bin folder.
ignite.sh ../config/cassandra-config.xml

Now, I want to take a look at the cassandra table via sqlline. I've tried the 
following:
./sqlline.sh -u jdbc:cassandra://172.16.129.68:9042/test  //(test is the name 
of the keyspace)

I get the following output:
No known driver to handle "jdbc:cassandra://172.16.129.68:9042/test". Searching 
for known drivers...
java.lang.NullPointerException
sqlline version 1.3.0
0: jdbc:cassandra://172.16.129.68:9042/test>

I've also tried:
./sqlline.sh -u jdbc:ignite:thin://172.16.129.68

but when I use "!tables", I'm not able to see any table.
What exactly has been missing? How to access/modify the tables present in 
Cassandra using sqlline?

Thanks and regards,
Vishal Sharma



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http://www.springframework.org/schema/beans;
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance;
   xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd;>





































172.16.129.68:47500..47509







http://www.springframework.org/schema/beans;
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance;
   xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd;>

















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RE: SSTable count in Nodetool tablestats(LevelCompactionStrategy)

[Vishal1.Sharma]

I used version: 3.11.2

I want to add that both the counts (SSTables, sum of numbers shown in levels), 
change after some time and become equal(i.e. the mismatch does not last 
forever) which has led me to believe that this mismatch happens only when the 
compaction process is going on and once the compaction is complete, the count 
becomes equal.

Regards,
Vishal Sharma

From: kurt greaves [mailto:k...@instaclustr.com]
Sent: Friday, April 20, 2018 12:27 PM
To: User
Subject: Re: SSTable count in Nodetool tablestats(LevelCompactionStrategy)

I'm currently investigating this issue on one of our clusters (but much worse, 
we're seeing >100 SSTables and only 2 in the levels) on 3.11.1. What version 
are you using? It's definitely a bug.

On 17 April 2018 at 10:09, 
> wrote:
Dear Community,

One of the tables in my keyspace is using LevelCompactionStrategy and when I 
used the nodetool tablestats keyspace.table_name command, I found some mismatch 
in the count of SSTables displayed at 2 different places. Please refer the 
attached image.

The command is giving SSTable count = 6 but if you add the numbers shown 
against SSTables in each level, then that comes out as 5. Why is there a 
difference?

Thanks and regards,
Vishal Sharma

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Cassandra read process

[Vishal1.Sharma]

Dear Community,

Can you please help in answering the question below:

https://stackoverflow.com/questions/49769643/cassandra-read-process

Thanks and regards,
Vishal Sharma
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SSTable count in Nodetool tablestats(LevelCompactionStrategy)

[Vishal1.Sharma]

Dear Community,

One of the tables in my keyspace is using LevelCompactionStrategy and when I 
used the nodetool tablestats keyspace.table_name command, I found some mismatch 
in the count of SSTables displayed at 2 different places. Please refer the 
attached image.

The command is giving SSTable count = 6 but if you add the numbers shown 
against SSTables in each level, then that comes out as 5. Why is there a 
difference?

Thanks and regards,
Vishal Sharma
"Confidentiality Warning: This message and any attachments are intended only 
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Memtable type and size allocation

[Vishal1.Sharma]

Dear Community,

In Cassandra 3.11.2, there are 3 choices for the type of Memtable allocation 
and as per my understanding, if I want to keep Memtables on JVM heap I can use 
heap_buffers and if I want to store Memtables outside of JVM heap then I've got 
2 options offheap_buffers and offheap_objects.

What exactly is the difference between the 2 choices given for off-heap 
allocation?

Also, the permitted memory space to be used for Memtables can be set at 2 
places in the YAML file, i.e. memtable_heap_space_in_mb and 
memtable_offheap_space_in_mb.

Do I need to configure some space in both heap and offheap, irrespective of the 
Memtable allocation type or do I need to set only one of them based on my 
Memtable allocation type i.e. memtable_heap_space_in_mb when using heap buffers 
and memtable_offheap_space_in_mb only when using either of the other 2 offheap 
options?

https://stackoverflow.com/questions/49874917/memtable-type-and-size-allocation

Thanks and regards,
Vishal Sharma
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