Re: RMI TCP Connection threads

[Vlad]

 Restarting Cassandra helped.

On Monday, July 29, 2019, 9:05:06 AM GMT+3, Dinesh Joshi 
 wrote:  
 
 Try obtaining a thread dump. It will help debug. Anything that goes via JMX 
such as nodetool could be responsible for it.
Dinesh


On Jul 28, 2019, at 10:57 PM, Vlad  wrote:
Hi,
suddenly I noticed that one of three nodes started consume CPU in RMI TCP 
Connection threads.

What it could be?
Thanks.


  

RMI TCP Connection threads

[Vlad]

Hi,
suddenly I noticed that one of three nodes started consume CPU in RMI TCP 
Connection threads.

What it could be?
Thanks.

Re: Compaction throughput

[Vlad]

 Thanks!

On Friday, July 19, 2019, 10:15:43 PM GMT+3, Jon Haddad 
 wrote:  
 
 It's a limit on the total compaction throughput. 
On Fri, Jul 19, 2019 at 10:39 AM Vlad  wrote:

Hi,
is  'nodetool setcompactionthroughput' sets limit for all compactions on the 
node, or is it per compaction thread?
Thanks.

  

Compaction throughput

[Vlad]

Hi,
is  'nodetool setcompactionthroughput' sets limit for all compactions on the 
node, or is it per compaction thread?
Thanks.

Re: Python driver concistency problem

[Vlad]

That's the issue - I do not use consistency ALL. I set QUORUM or ONE but it 
still performs with ALL. 

On Wednesday, May 22, 2019 12:42 PM, shalom sagges  
wrote:
 

 In a lot of cases, the issue is with the data model. 
Can you describe the table?
Can you provide the query you use to retrieve the data?What's the load on your 
cluster?Are there lots of tombstones?
You can set the consistency level to ONE, just to check if you get responses. 
Although normally I would never use ALL unless I run a DDL command. 
I prefer local_quorum if I want my consistency to be strong while keeping 
Cassandra's high availability. 

Regards,






   

Re: Python driver concistency problem

[Vlad]

Hi,
I do reads in my own Python code, how cqlsh can affect it? 

On Wednesday, May 22, 2019 12:02 PM, Chakravarthi Manepalli 
 wrote:
 

 Hi Vlad,
Maybe the consistency level has been set manually in CQLSH. Did you try 
checking your consistency level and set it back to normal? (Just a thought, Not 
sure!!)
On Wed, May 22, 2019 at 2:00 PM Vlad  wrote:

Hi,
we have three nodes cluster with KS defined as 

CREATE KEYSPACE someks WITH REPLICATION = { 'class' : 
'org.apache.cassandra.locator.NetworkTopologyStrategy', 'some-dc': '3' } AND 
DURABLE_WRITES = true;

next I read with Pyhton (cassandra-driver 3.11) from Cassandra 3.11.3 and get 
error 

Error from server: code=1200 [Coordinator node timed out waiting for replica 
nodes' responses] message="Operation timed out - received only 2 responses." 
info={'received_responses': 2, 'required_responses': 3, 'consistency': 'ALL'}
nor session.default_consistency_level = ConsistencyLevel.QUORUM neither 
query = SimpleStatement("SELECT **", 
consistency_level=ConsistencyLevel.QUORUM)
rows = session.execute(query)

helps. What it could be?

Thanks in advance.




   

Python driver concistency problem

[Vlad]

Hi,
we have three nodes cluster with KS defined as 

CREATE KEYSPACE someks WITH REPLICATION = { 'class' : 
'org.apache.cassandra.locator.NetworkTopologyStrategy', 'some-dc': '3' } AND 
DURABLE_WRITES = true;

next I read with Pyhton (cassandra-driver 3.11) from Cassandra 3.11.3 and get 
error 

Error from server: code=1200 [Coordinator node timed out waiting for replica 
nodes' responses] message="Operation timed out - received only 2 responses." 
info={'received_responses': 2, 'required_responses': 3, 'consistency': 'ALL'}
nor session.default_consistency_level = ConsistencyLevel.QUORUM neither 
query = SimpleStatement("SELECT **", 
consistency_level=ConsistencyLevel.QUORUM)
rows = session.execute(query)

helps. What it could be?

Thanks in advance.

Re: Wrong concistency level

[Vlad]

Hi, thanks for answer.
what I don't understand is:

- why there are attempts of read repair if repair chances are 0.0 ?- what can 
be cause for big mutation size?- why hinted handoffs didn't prevent 
inconsistency? (because of  big mutation size?)

Thanks. 

On Tuesday, January 1, 2019 9:41 PM, Jeff Jirsa  wrote:
 

 Read repair due to digest mismatch and speculative retry can both cause some 
behaviors that are hard to reason about (usually seen if a host stops accepting 
writes due to bad disk, which you havent described, but generally speaking, 
there are times when reads will block on writing to extra replicas). 
The patch from https://issues.apache.org/jira/browse/CASSANDRA-10726 changes 
this behavior significantly.
The last message in this thread (about huge read repair mutations) suggests 
that your writes during the bounce got some partitions quite out of sync, and 
hints aren't replaying fast enough to fill in the gaps before you read, and the 
read repair is timing out. The read repair timing out wouldn't block the read 
after 10726, so if you're seeing read timeouts right now, what you probably 
want to do is run repair or read much smaller pages so that read repair 
succeeds, or increase your commitlog segment size from 32M to 128M or so until 
the read repair actually succeeds. 

On Tue, Jan 1, 2019 at 12:18 AM Vlad  wrote:

Hi All and Happy New Year!!!
This year started with Cassandra 3.11.3 sometimes forces level ALL despite 
query level LOCAL_QUORUM (actually there is only one DC) and it fails with 
timeout.
As far as I understand, it can be caused by read repair attempts (we see 
"DigestMismatch" errors in Cassandra log), but table has no read repair 
configured:
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 
'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 
'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 
'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.0
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';


Any suggestions?
Thanks.



   

Re: Wrong concistency level

[Vlad]

Also I see 
WARN  [ReadRepairStage:341] 2018-12-31 17:57:58,594 DataResolver.java:507 - 
Encountered an oversized (37264537/16777216) read repair mutation for table
for about several hours (5-7) after cluster restart, next it disappeared. 

On Tuesday, January 1, 2019 1:10 PM, Vlad  
wrote:
 

 Actually what happened is that Cassandra instances was upgraded to bigger size 
one by one, with downtime about one-two minutes each. There are logs
INFO  [HintsDispatcher:3] 2018-12-31 11:23:48,305 
HintsDispatchExecutor.java:282 - Finished hinted handoff of file 
d2c7bb82-3d7a-43b2-8791-ef9c7c02b2c1-1546182664318-1.hints to endpoint 
/10.123.123.123: d2c7bb82-3d7a-43b2-8791-ef9c7c02b2c1

And from now on there is lot of Digest Mismatch exceptions in Cassandra log.
What's going on?


 

On Tuesday, January 1, 2019 10:18 AM, Vlad  
wrote:
 

 Hi All and Happy New Year!!!
This year started with Cassandra 3.11.3 sometimes forces level ALL despite 
query level LOCAL_QUORUM (actually there is only one DC) and it fails with 
timeout.
As far as I understand, it can be caused by read repair attempts (we see 
"DigestMismatch" errors in Cassandra log), but table has no read repair 
configured:
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 
'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 
'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 
'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.0
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';


Any suggestions?
Thanks.


   

   

Re: Wrong concistency level

[Vlad]

Actually what happened is that Cassandra instances was upgraded to bigger size 
one by one, with downtime about one-two minutes each. There are logs
INFO  [HintsDispatcher:3] 2018-12-31 11:23:48,305 
HintsDispatchExecutor.java:282 - Finished hinted handoff of file 
d2c7bb82-3d7a-43b2-8791-ef9c7c02b2c1-1546182664318-1.hints to endpoint 
/10.123.123.123: d2c7bb82-3d7a-43b2-8791-ef9c7c02b2c1

And from now on there is lot of Digest Mismatch exceptions in Cassandra log.
What's going on?


 

On Tuesday, January 1, 2019 10:18 AM, Vlad  
wrote:
 

 Hi All and Happy New Year!!!
This year started with Cassandra 3.11.3 sometimes forces level ALL despite 
query level LOCAL_QUORUM (actually there is only one DC) and it fails with 
timeout.
As far as I understand, it can be caused by read repair attempts (we see 
"DigestMismatch" errors in Cassandra log), but table has no read repair 
configured:
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 
'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 
'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 
'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.0
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';


Any suggestions?
Thanks.


   

Wrong concistency level

[Vlad]

Hi All and Happy New Year!!!
This year started with Cassandra 3.11.3 sometimes forces level ALL despite 
query level LOCAL_QUORUM (actually there is only one DC) and it fails with 
timeout.
As far as I understand, it can be caused by read repair attempts (we see 
"DigestMismatch" errors in Cassandra log), but table has no read repair 
configured:
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 
'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 
'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 
'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.0
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';


Any suggestions?
Thanks.

Re: Scrub - autocompaction

[Vlad]

Hi
>you should reach an end as the scrub is applied to a list of sstables 
>calculated scrub start (I believe).What I observed is that in data folder 
>almost no original SSTables remained, but scrub still ran. So I suspect 
>processing each new appearing table.
 

On Monday, October 29, 2018 8:34 PM, Alain RODRIGUEZ  
wrote:
 

 Hello,

should autocompaction be disabled before running scrub?


I would say the other way around, to be sure to leave some room to regular 
compactions, you could try to run scrub with the following option
`nodetool scrub -j 1` (-j / --jobs allow controlling the number of compactor 
threads to use). Depending on the rhythm you want to give to compaction 
operations, you can tune this number and the ‘concurrent_compactor' option.

It seems that scrub processes each new created table and never ends.

Depending on the command that was run, if nothing was specified, nodetool scrub 
might be running on the whole node (or keyspace?), which can be a lot, so when 
an SSTable finishes, another might well start, for quite a while. But you 
should reach an end as the scrub is applied to a list of sstables calculated 
scrub start (I believe).
Here is what I can share from my understanding. If you believe there might be 
an issue with your version of Cassandra or want to make sure that 'nodetool 
scrub' behaves as described, reading the code and/or observing writ time of the 
files that are getting compacted (SCRUB) is a way to go.
C*heers,---Alain Rodriguez - alain@thelastpickle.comFrance 
/ Spain
The Last Pickle - Apache Cassandra Consultinghttp://www.thelastpickle.com


Le lun. 29 oct. 2018 à 16:18, Vlad  a écrit :

Hi,
should autocompaction be disabled before running scrub?It seems that scrub 
processes each new created table and never ends.
Thanks.



   

Scrub - autocompaction

[Vlad]

Hi,
should autocompaction be disabled before running scrub?It seems that scrub 
processes each new created table and never ends.
Thanks.

Re: Refering to non-existing node

[Vlad]

Hi, this node isn't in system.peers on both nodes. 

On Thursday, September 6, 2018 10:02 PM, Michael Shuler 
 wrote:
 

 On 09/06/2018 01:48 PM, Vlad wrote:
> Hi,
> 3 node cluster, Cassandra 3.9, GossipingPropertyFileSnitch, one DC
> 
> I removed dead node with `nodetool assassinate`. It was also seed node,
> so I removed it from seeds list on two other nodes and restarted them.
> 
> But I still see in log
> `DEBUG [GossipTasks:1] 2018-09-06 18:32:05,149 Gossiper.java:337 -
> Convicting /10.100.129.116 with status LEFT - alive false`
> 
> 
> What does this log mean? How can I get rid of this?

https://twitter.com/faltering/status/559845791741657088

If you *only* used assassinate, without moving through the removal
steps, then the node is still in the system.peers (I think) table on
some or all of the nodes.

-- 
Michael

-
To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org
For additional commands, e-mail: user-h...@cassandra.apache.org



   

Re: URGENT: disable reads from node

[Vlad]

Hi,
this node isn't in system.peers on both nodes. 

On Wednesday, August 29, 2018 4:22 PM, Vlad  
wrote:
 

 Hi,
>You'll need to disable the native transportWell, this is what I did already, 
>it seems repair is running

I'm not sure whether repair will finish within 3 hours, but I can run it again 
(as it's incremental repair by default, right?)


I'm not sure about RF=3 and QUORUM reads because of load/disk space constrains 
we have, but we'll definitely consider this.

Thanks to all for help!
 

On Wednesday, August 29, 2018 4:13 PM, Alexander Dejanovski 
 wrote:
 

 Kurt is right. 
So here are the options I can think of : - use the join_ring false technique 
and rely on hints. You'll need to disable the native transport on the node as 
well to prevent direct connections to be made to it. Hopefully, you can run 
repair in less than 3 hours which is the hint window (hints will be collected 
while the node hasn't joined the ring). Otherwise you'll have more consistency 
issues after the node joins the ring again. Maybe incremental repair could help 
fixing this quickly afterwards if you've been running full repairs that 
involved anticompaction (if you're running at least Cassandra 2.2).- Fully 
re-bootstrap the node by replacing itself, using the replace_address_first_boot 
technique (but since you have RF=2, that would most probably mean some data 
loss since you read/write at ONE)- Try to cheat the dynamic snitch to take the 
node out of reads. You would then have the node join the ring normally, disable 
native transport and raise Severity (in 
org.apache.cassandra.db:type=DynamicEndpointSnitch) to something like 50 so the 
node won't be selected by the dynamic snitch. I guess the value will reset 
itself over time so you may need to set it to 50 on a regular basis while 
repair is happening.
I would then strongly consider moving to RF=3 because RF=2 will lead you to 
this type of situation again in the future and does not allow quorum reads with 
fault tolerance. Good luck,
On Wed, Aug 29, 2018 at 1:56 PM Vlad  wrote:

I restarted with cassandra.join_ring=falsenodetool status on other nodes shows 
this node as DN, while it see itself as UN.


>I'd say best to just query at QUORUM until you can finish repairs.We have RH 
>2, so I guess QUORUM queries will fail. Also different application should be 
>changed for this. 

On Wednesday, August 29, 2018 2:41 PM, kurt greaves  
wrote:
 

 Note that you'll miss incoming writes if you do that, so you'll be 
inconsistent even after the repair. I'd say best to just query at QUORUM until 
you can finish repairs.
On 29 August 2018 at 21:22, Alexander Dejanovski  wrote:

Hi Vlad, you must restart the node but first disable joining the cluster, as 
described in the second part of this blog post : 
http://thelastpickle.com/blog/ 2018/08/02/Re-Bootstrapping- 
Without-Bootstrapping.html
Once repaired, you'll have to run "nodetool join" to start serving reads.

Le mer. 29 août 2018 à 12:40, Vlad  a écrit :

Will it help to set read_repair_chance to 1 (compaction is 
SizeTieredCompactionStrategy)? 

On Wednesday, August 29, 2018 1:34 PM, Vlad  
wrote:
 

 Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.


   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com



   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com

   

   

Refering to non-existing node

[Vlad]

Hi,3 node cluster, Cassandra 3.9, GossipingPropertyFileSnitch, one DC

I removed dead node with `nodetool assassinate`. It was also seed node, so I 
removed it from seeds list on two other nodes and restarted them.
But I still see in log 
`DEBUG [GossipTasks:1] 2018-09-06 18:32:05,149 Gossiper.java:337 - Convicting 
/10.100.129.116 with status LEFT - alive false`

What does this log mean? How can I get rid of this?
Thanks.

Re: URGENT: disable reads from node

[Vlad]

Hi,
>You'll need to disable the native transportWell, this is what I did already, 
>it seems repair is running

I'm not sure whether repair will finish within 3 hours, but I can run it again 
(as it's incremental repair by default, right?)


I'm not sure about RF=3 and QUORUM reads because of load/disk space constrains 
we have, but we'll definitely consider this.

Thanks to all for help!
 

On Wednesday, August 29, 2018 4:13 PM, Alexander Dejanovski 
 wrote:
 

 Kurt is right. 
So here are the options I can think of : - use the join_ring false technique 
and rely on hints. You'll need to disable the native transport on the node as 
well to prevent direct connections to be made to it. Hopefully, you can run 
repair in less than 3 hours which is the hint window (hints will be collected 
while the node hasn't joined the ring). Otherwise you'll have more consistency 
issues after the node joins the ring again. Maybe incremental repair could help 
fixing this quickly afterwards if you've been running full repairs that 
involved anticompaction (if you're running at least Cassandra 2.2).- Fully 
re-bootstrap the node by replacing itself, using the replace_address_first_boot 
technique (but since you have RF=2, that would most probably mean some data 
loss since you read/write at ONE)- Try to cheat the dynamic snitch to take the 
node out of reads. You would then have the node join the ring normally, disable 
native transport and raise Severity (in 
org.apache.cassandra.db:type=DynamicEndpointSnitch) to something like 50 so the 
node won't be selected by the dynamic snitch. I guess the value will reset 
itself over time so you may need to set it to 50 on a regular basis while 
repair is happening.
I would then strongly consider moving to RF=3 because RF=2 will lead you to 
this type of situation again in the future and does not allow quorum reads with 
fault tolerance. Good luck,
On Wed, Aug 29, 2018 at 1:56 PM Vlad  wrote:

I restarted with cassandra.join_ring=falsenodetool status on other nodes shows 
this node as DN, while it see itself as UN.


>I'd say best to just query at QUORUM until you can finish repairs.We have RH 
>2, so I guess QUORUM queries will fail. Also different application should be 
>changed for this. 

On Wednesday, August 29, 2018 2:41 PM, kurt greaves  
wrote:
 

 Note that you'll miss incoming writes if you do that, so you'll be 
inconsistent even after the repair. I'd say best to just query at QUORUM until 
you can finish repairs.
On 29 August 2018 at 21:22, Alexander Dejanovski  wrote:

Hi Vlad, you must restart the node but first disable joining the cluster, as 
described in the second part of this blog post : 
http://thelastpickle.com/blog/ 2018/08/02/Re-Bootstrapping- 
Without-Bootstrapping.html
Once repaired, you'll have to run "nodetool join" to start serving reads.

Le mer. 29 août 2018 à 12:40, Vlad  a écrit :

Will it help to set read_repair_chance to 1 (compaction is 
SizeTieredCompactionStrategy)? 

On Wednesday, August 29, 2018 1:34 PM, Vlad  
wrote:
 

 Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.


   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com



   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com

   

Re: URGENT: disable reads from node

[Vlad]

Also after restart with join_ring=false C* is still accepting connection on 
port 9042 (and obviously returning no data), so I run nodetool drainIs it good?
I run nodetool repair on this node. Meanwhile command didn't return, but I see 
in log
INFO  [Thread-6] 2018-08-29 12:16:03,954 RepairRunnable.java:125 - Starting 
repair command #1, repairing keyspace scanrepo with repair options 
(parallelism: parallel, primary range: false, incremental: true, job threads: 
1, ColumnFamilies: [], dataCenters: [], hosts: [], # of ranges: 530)
ERROR [Thread-6] 2018-08-29 12:16:14,363 SystemDistributedKeyspace.java:306 - 
Error executing query INSERT INTO system_distributed.parent_repair_history 
(parent_id, keyspace_name, columnfamily_names, requested_ranges, started_at,
  options) VALUES (...) 
org.apache.cassandra.exceptions.WriteTimeoutException: Operation timed out - 
received only 0 responses.

and  nodetool compactionstats shows 
pending tasks: 9
- system_schema.tables: 1
- system_schema.keyspaces: 1
- ks1.tb1: 4
- ks1.tb2: 3


 

On Wednesday, August 29, 2018 2:57 PM, Vlad  
wrote:
 

 I restarted with cassandra.join_ring=falsenodetool status on other nodes shows 
this node as DN, while it see itself as UN.


>I'd say best to just query at QUORUM until you can finish repairs.We have RH 
>2, so I guess QUORUM queries will fail. Also different application should be 
>changed for this. 

On Wednesday, August 29, 2018 2:41 PM, kurt greaves  
wrote:
 

 Note that you'll miss incoming writes if you do that, so you'll be 
inconsistent even after the repair. I'd say best to just query at QUORUM until 
you can finish repairs.
On 29 August 2018 at 21:22, Alexander Dejanovski  wrote:

Hi Vlad, you must restart the node but first disable joining the cluster, as 
described in the second part of this blog post : 
http://thelastpickle.com/blog/ 2018/08/02/Re-Bootstrapping- 
Without-Bootstrapping.html
Once repaired, you'll have to run "nodetool join" to start serving reads.

Le mer. 29 août 2018 à 12:40, Vlad  a écrit :

Will it help to set read_repair_chance to 1 (compaction is 
SizeTieredCompactionStrategy)? 

On Wednesday, August 29, 2018 1:34 PM, Vlad  
wrote:
 

 Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.


   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com



   

   

Re: URGENT: disable reads from node

[Vlad]

I restarted with cassandra.join_ring=falsenodetool status on other nodes shows 
this node as DN, while it see itself as UN.


>I'd say best to just query at QUORUM until you can finish repairs.We have RH 
>2, so I guess QUORUM queries will fail. Also different application should be 
>changed for this. 

On Wednesday, August 29, 2018 2:41 PM, kurt greaves  
wrote:
 

 Note that you'll miss incoming writes if you do that, so you'll be 
inconsistent even after the repair. I'd say best to just query at QUORUM until 
you can finish repairs.
On 29 August 2018 at 21:22, Alexander Dejanovski  wrote:

Hi Vlad, you must restart the node but first disable joining the cluster, as 
described in the second part of this blog post : 
http://thelastpickle.com/blog/ 2018/08/02/Re-Bootstrapping- 
Without-Bootstrapping.html
Once repaired, you'll have to run "nodetool join" to start serving reads.

Le mer. 29 août 2018 à 12:40, Vlad  a écrit :

Will it help to set read_repair_chance to 1 (compaction is 
SizeTieredCompactionStrategy)? 

On Wednesday, August 29, 2018 1:34 PM, Vlad  
wrote:
 

 Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.


   
-- 
-Alexander DejanovskiFrance@alexanderdeja
ConsultantApache Cassandra Consultinghttp://www.thelastpickle.com



   

Re: URGENT: disable reads from node

[Vlad]

Will it help to set read_repair_chance to 1 (compaction is 
SizeTieredCompactionStrategy)? 

On Wednesday, August 29, 2018 1:34 PM, Vlad  
wrote:
 

 Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.


   

URGENT: disable reads from node

[Vlad]

Hi,
quite urgent questions:due to disk and C* start problem we were forced to 
delete commit logs from one of nodes.
Now repair is running, but meanwhile some reads bring no data (RF=2)

Can this node be excluded from reads queries? And that  all reads will be 
redirected to other node in the ring?

Thanks to All for help.

Re: ALTER default_time_to_live

[Vlad]

Hi, thanks for answer!
I've read article about TWCS, and I don't understand how claim 

"When rows reach their TTL (10 minutes here), they turn into tombstones. Our 
table defines that tombstones can be purged 1 minute after they were created.If 
all rows are created with the same TTL, SSTables will get 100% droppable 
tombstones eventually and perform full SSTable deletion instead of purging 
tombstones through compaction."

goes with 
"Once the major compaction for a time window is completed, no further 
compaction of the data will ever occur."

In above example TTL is 10 minutes, but time window is only one. As far as I 
understand C* never compacts passed bucket. Does it check tombstones anyway? 

On Thursday, January 18, 2018 1:32 PM, Alain RODRIGUEZ <arodr...@gmail.com> 
wrote:
 

 
I set  default_time_to_live for existing table. Does it affect existing data?

No, it sets a default TTL for the future writes (that is no guarantee, as it 
can be overwritten in any specific query).

It seems data to be deleted, but after compaction, I don't see any disk space 
freed as expected

Indeed tombstones are responsible for tombstones eviction, yet there are some 
conditions to respect to be able to remove the tombstones (for consistency 
reasons). I detailed this last year, and even though the content is a bit old, 
main principles are still true and the tuning options are still relevant.
About deletes and tombstones: 
http://thelastpickle.com/blog/2016/07/27/about-deletes-and-tombstones.html
tl;dr: I would give a try to unchecked_tombstone_compaction: true. Maybe also 
consider using TWCS because of this "TTL is also ten days on one table and 100 
days on other.". But I really recommend you to understand how this all work to 
act wisely. My guess can be wrong.
About TWCS: http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html
C*heers,---Alain Rodriguez - @arodream - 
alain@thelastpickle.comFrance / Spain
The Last Pickle - Apache Cassandra Consultinghttp://www.thelastpickle.com
2018-01-18 11:15 GMT+00:00 Vlad <qa23d-...@yahoo.com.invalid>:

Hi,
I set  default_time_to_live for existing table. Does it affect existing data? 
It seems data to be deleted, but after compaction, I don't see any disk space 
freed as expected. Database has data for almost year, GC time is ten days, and 
TTL is also ten days on one table and 100 days on other.
 Cassandra version 3.11.0

Thanks.




   

ALTER default_time_to_live

[Vlad]

Hi,
I set  default_time_to_live for existing table. Does it affect existing data? 
It seems data to be deleted, but after compaction, I don't see any disk space 
freed as expected. Database has data for almost year, GC time is ten days, and 
TTL is also ten days on one table and 100 days on other.
 Cassandra version 3.11.0

Thanks.

Anticompaction

[Vlad]

Hi,
I run repair, then I see that anticompaction started on all nodes.Does it mean 
that all data is already repaired. Actually I increased RF, so can I already 
use database?
Thanks.

Re: Large tombstones creation

[Vlad]

Hi,
that's the issue, thanks! 

On Sunday, August 13, 2017 2:49 PM, Christophe Schmitz 
<christo...@instaclustr.com> wrote:
 

 Hi Vlad,
Are you by any chance inserting null values? If so you will create tombstones. 
The work around (Cassandra >= 2.2) is to use unset on your bound statement (see 
https://issues.apache.org/jira/browse/CASSANDRA-7304)
Cheers,
Christophe
On 13 August 2017 at 20:48, Vlad <qa23d-...@yahoo.com.invalid> wrote:

Hi,
I insert about 45000 rows to empty table in Python using prepared statements 
and IF NOT EXISTS. While reading after insert I get warnings likeServer 
warning: Read 5000 live rows and 33191 tombstone cells for query SELECT * FROM 
...  LIMIT 5000 (see tombstone_warn_threshold)

How it can happen? I have several SASI indexes for this table, can this be a 
reason?
Regards, Vlad




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Christophe Schmitz
Director of consulting EMEA
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Large tombstones creation

[Vlad]

Hi,
I insert about 45000 rows to empty table in Python using prepared statements 
and IF NOT EXISTS. While reading after insert I get warnings likeServer 
warning: Read 5000 live rows and 33191 tombstone cells for query SELECT * FROM 
...  LIMIT 5000 (see tombstone_warn_threshold)

How it can happen? I have several SASI indexes for this table, can this be a 
reason?
Regards, Vlad

SASI and secondary index simultaniously

[Vlad]

Hi,
it's possible to create both regular secondary index and SASI on the same 
column:
CREATE TABLE ks.tb (id int PRIMARY KEY,  name text);
CREATE CUSTOM INDEX tb_name_idx_1 ON ks.tb (name) USING 
'org.apache.cassandra.index.sasi.SASIIndex';
CREATE INDEX tb_name_idx ON ks.tb (name);

 But which one is used for SELECT? Assuming we have regular index and would 
like to migrate to SASI, can we first create SASI, than drop regular? And how 
can we check then index build is completed?
Thanks.

stress tool: random seed

[Vlad]

Hi,
I'm populating database with YAML. Each time I run stress tool I get the same 
rows, i.e. the same data generated and no new rows appear.
Is there any option to generate each time new data? I would like to test 
growing database, but don't want insert each time all data.
I found a kind of workaround by changing partition key distribution boundaries, 
but is there better way?
Regards, Vlad

Re: Multiple nodes decommission

[Vlad]

>There's a system property (actually 2)Which ones?
 

On Wednesday, April 19, 2017 9:17 AM, Jeff Jirsa <jji...@apache.org> wrote:
 

 

On 2017-04-12 11:30 (-0700), Vlad <qa23d-...@yahoo.com> wrote: 
> Interesting, there is no such explicit warning for v.3 
> https://docs.datastax.com/en/cassandra/3.0/cassandra/operations/opsAddNodeToCluster.html
> It says  
>    - Start the bootstrap node.
>    - verify that the node is fully bootstrapped and all other nodes are up 
>(UN)
> 
> Does it mean that we should start them one by one? May somebody from 
> developers can clarify this issue? 

You should treat range movements (bootstrap/decom/etc) in 3.0 the same way you 
treated 2.0/2.1/2.2 - there's nothing special (as far as I know) to make it any 
more safe than 2.x was.

The warnings and restrictions are because simultaneous range movements PROBABLY 
violate your assumed consistency guarantees if you're using vnodes. If you're 
using single token, this can be avoided. 

If you really know what you're doing, you can tell cassandra to let you do 
simultaneous range movements anyway. There's a system property (actually 2) 
that will let you tell cassandra you know the tradeoffs, and then you can 
bootstrap/decom/etc more than one node at a time. Generally, it's one of those 
things where if you have to ask about it, you probably should just stick to the 
default one-at-a-time guidelines (which isn't meant to sound condescending, but 
it's an area where you can definitely violate consistency and maybe even lose 
data if you're not sure).

- Jeff


   

Spark node: use 127.0.0.1 for connection to Cassandra

[Vlad]

Hi All,
I have Cassandra with Spark on node 10.0.0.1

On other server I run 
./spark-shell --master spark://10.0.0.1:7077and then set 
val conf = new SparkConf(true).set("spark.cassandra.connection.host", 
"10.0.0.1")
It works, but I see in tcpdump that Spark node connects to Cassandra with 
address 10.0.0.1How can I cause node to use 127.0.0.1 (Cassandra listens on 
0.0.0.0:9042) ?

Thanks.

Re: Multiple nodes decommission

[Vlad]

>range reassignments which becomes effective after a successful decommission.
But during leaving nodes announce themselves as "leaving". Do other leaving 
nodes taking this into account and not stream data to them? (applicable also 
for joining). I hope so ))

I guess problem with sequential adding/removing nodes is data overstreaming and 
non-even load distribution. I mean if we have three racks it's better to 
add/remove by three nodes (one in each rack) and to avoid state with four 
nodes, for example.

Any thoughts?
 

On Tuesday, April 11, 2017 7:55 PM, benjamin roth <brs...@gmail.com> wrote:
 

 I did not test it but I'd bet that parallel decommision will lead to 
inconsistencies.Each decommission results in range movements and range 
reassignments which becomes effective after a successful decommission.If you 
start several decommissions at once, I guess the calculated reassignments are 
invalid for at least one node after the first node finished the decommission 
process.
I hope someone will correct me if i am wrong.
2017-04-11 18:43 GMT+02:00 Jacob Shadix <jacobsha...@gmail.com>:

Are you using vnodes? I typically do one-by-one as the decommission will create 
additional load/network activity streaming data to the other nodes as the token 
ranges are reassigned. 
-- Jacob Shadix 

On Sat, Apr 8, 2017 at 10:55 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hi,
how multiple nodes should be decommissioned by "nodetool decommission"- one by 
one or in parallel ?

Thanks.






   

Re: Multiple nodes decommission

[Vlad]

Interesting, there is no such explicit warning for v.3 
https://docs.datastax.com/en/cassandra/3.0/cassandra/operations/opsAddNodeToCluster.html
It says   
   - Start the bootstrap node.
   - verify that the node is fully bootstrapped and all other nodes are up (UN)

Does it mean that we should start them one by one? May somebody from developers 
can clarify this issue? 

On Wednesday, April 12, 2017 9:16 PM, Jacob Shadix <jacobsha...@gmail.com> 
wrote:
 

 It's still not recommended to start at the same time. Stagger by 2 minutes is 
what the following documentation suggests; along with additional steps. re. 
version 2.1
https://docs.datastax.com/en/cassandra/2.1/cassandra/operations/ops_add_node_to_cluster_t.html

-- Jacob Shadix 

On Wed, Apr 12, 2017 at 1:48 PM, Vlad <qa23d-...@yahoo.com> wrote:

But it seems OK to add multiple nodes at once, right?
 

On Tuesday, April 11, 2017 8:38 PM, Jacob Shadix <jacobsha...@gmail.com> 
wrote:
 

 Right! Another reason why I just stick with sequential decommissions. Maybe 
someone here could shed some light on what happens under the covers if parallel 
decommissions are kicked off.
-- Jacob Shadix 

On Tue, Apr 11, 2017 at 12:55 PM, benjamin roth <brs...@gmail.com> wrote:

I did not test it but I'd bet that parallel decommision will lead to 
inconsistencies.Each decommission results in range movements and range 
reassignments which becomes effective after a successful decommission.If you 
start several decommissions at once, I guess the calculated reassignments are 
invalid for at least one node after the first node finished the decommission 
process.
I hope someone will correct me if i am wrong.
2017-04-11 18:43 GMT+02:00 Jacob Shadix <jacobsha...@gmail.com>:

Are you using vnodes? I typically do one-by-one as the decommission will create 
additional load/network activity streaming data to the other nodes as the token 
ranges are reassigned. 
-- Jacob Shadix 

On Sat, Apr 8, 2017 at 10:55 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hi,
how multiple nodes should be decommissioned by "nodetool decommission"- one by 
one or in parallel ?

Thanks.








   



   

Re: Multiple nodes decommission

[Vlad]

But it seems OK to add multiple nodes at once, right?
 

On Tuesday, April 11, 2017 8:38 PM, Jacob Shadix <jacobsha...@gmail.com> 
wrote:
 

 Right! Another reason why I just stick with sequential decommissions. Maybe 
someone here could shed some light on what happens under the covers if parallel 
decommissions are kicked off.
-- Jacob Shadix 

On Tue, Apr 11, 2017 at 12:55 PM, benjamin roth <brs...@gmail.com> wrote:

I did not test it but I'd bet that parallel decommision will lead to 
inconsistencies.Each decommission results in range movements and range 
reassignments which becomes effective after a successful decommission.If you 
start several decommissions at once, I guess the calculated reassignments are 
invalid for at least one node after the first node finished the decommission 
process.
I hope someone will correct me if i am wrong.
2017-04-11 18:43 GMT+02:00 Jacob Shadix <jacobsha...@gmail.com>:

Are you using vnodes? I typically do one-by-one as the decommission will create 
additional load/network activity streaming data to the other nodes as the token 
ranges are reassigned. 
-- Jacob Shadix 

On Sat, Apr 8, 2017 at 10:55 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hi,
how multiple nodes should be decommissioned by "nodetool decommission"- one by 
one or in parallel ?

Thanks.








   

Multiple nodes decommission

[Vlad]

Hi,
how multiple nodes should be decommissioned by "nodetool decommission"- one by 
one or in parallel ?

Thanks.

Re: system_auth replication strategy

[Vlad]

Actually if factor is equal to total number of nodes with SimpleStrategy one 
copy will be placed on each node.Does LOCAL_ONE know to choose local (the same) 
node with SimpleStrategy? 

On Sunday, April 2, 2017 4:02 PM, Sam Tunnicliffe  wrote:
 

 
auth logins for super users is 101 replicas serving the read

This only applies to the default superuser (i.e. 'cassandra'), which is one of 
the reasons for recommending it is only used during initial setup[1]. Reads for 
all other users, including superusers, are done at LOCAL_ONE
[1] 
http://cassandra.apache.org/doc/latest/operating/security.html#authentication
On Sun, Apr 2, 2017 at 7:07 AM, Jeff Jirsa  wrote:

> You should use a network topology strategy with high RF in each DC


There's some debate here - some blogs/speakers will say to put a replica on 
each instance, but that falls down above a few dozen instances. Imagine if you 
have (for example) 200 instances per DC, auth logins for super users is 101 
replicas serving the read - that's a really slow login that's likely to fail 
(think about thread pools on the coordinator doing the read response handling, 
it's an ugly ugly mess).

Normal logins do use LOCAL_ONE though so if there are lots of replicas, auth 
will be faster - so use 5-10 replicas per DC, and crank up the caching timeouts 
as well





   

system_auth replication strategy

[Vlad]

Hi,
what is the suitable replication strategy for system_auth keyspace?As I 
understand factor should be equal to total nodes number, so can we use 
SimpleStrategy? Does it ensure that queries with LOCAL_ONE consistency level 
will be targeted to local DC (or the same node)?
Thanks.

Re: Two DCs assandra on Azure connection problem.

[Vlad]

Hi Cliff,great, it helps, thank you!

So it's still strange for me why - as I mentioned "I suspected connectivity 
problem, but tcpdump shows constant traffic on port 7001 between nodes.", and 
even in unresponsive state there was packet exchange. Also I don't see in 
Cassandra code enabling SO_KEEPALIVE on storage port, only on CQL 
port.Nevertheless it works now, thanks again!


Here is link to MSDN about this timeout - 
https://blogs.msdn.microsoft.com/cie/2014/02/13/windows-azure-load-balancer-timeout-for-cloud-service-roles-paas-webworker/
Regards, Vlad
 
   

 On Thursday, October 27, 2016 8:50 PM, Cliff Gilmore <cgilm...@datastax.com> 
wrote:
 

 Azure has aggressively low keepalive settings for it's networks. Ignore the 
Mongo parts of this link and have a look at the OS settings they change.
https://docs.mongodb.com/ecosystem/platforms/windows-azure/

---
Cliff Gilmore
Vanguard Solutions ArchitectM: 314-825-4413
DataStax, Inc. | www.DataStax.com


On Thu, Oct 27, 2016 at 5:48 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hello,
I put two nodes cluster on Azure. Each node in its own DC (ping about 10 ms.), 
inter-node connection (SSL port 7001) is going throw external IPs, i.e.

 listen_interface: eth0broadcast_address: 1.1.1.1
Cluster is starting, cqlsh can connect, stress-tool survives night of writes 
with replication factor two, all seems to be fine. But when cluster is leaved 
without load it becomes nonfunctional after several minutes of idle. Attempt to 
connect fails with error
Connection error: ('Unable to connect to any servers', {'1.1.1.1': 
OperationTimedOut('errors= Timed out creating connection (10 seconds), 
last_host=None',)})

There is messageWARN  10:06:32 RequestExecutionException READ_TIMEOUT: 
Operation timed out - received only 1 responses.

on one node six minutes after start (no load or connect in this time).

nodetool status shows both nodes as UN (Up and Normal, I guess) 

I suspected connectivity problem, but tcpdump shows constant traffic on port 
7001 between nodes. Restarting OTHER node than I'm connection to solves the 
problem for another several minutes. I increased  TCP idle time in Azure IP 
address setting to 30 minutes, but it had no effect.

Thanks, Vlad






   

Two DCs assandra on Azure connection problem.

[Vlad]

Hello,
I put two nodes cluster on Azure. Each node in its own DC (ping about 10 ms.), 
inter-node connection (SSL port 7001) is going throw external IPs, i.e.

 listen_interface: eth0broadcast_address: 1.1.1.1
Cluster is starting, cqlsh can connect, stress-tool survives night of writes 
with replication factor two, all seems to be fine. But when cluster is leaved 
without load it becomes nonfunctional after several minutes of idle. Attempt to 
connect fails with error
Connection error: ('Unable to connect to any servers', {'1.1.1.1': 
OperationTimedOut('errors=Timed out creating connection (10 seconds), 
last_host=None',)})

There is messageWARN  10:06:32 RequestExecutionException READ_TIMEOUT: 
Operation timed out - received only 1 responses.

on one node six minutes after start (no load or connect in this time).

nodetool status shows both nodes as UN (Up and Normal, I guess) 

I suspected connectivity problem, but tcpdump shows constant traffic on port 
7001 between nodes. Restarting OTHER node than I'm connection to solves the 
problem for another several minutes. I increased  TCP idle time in Azure IP 
address setting to 30 minutes, but it had no effect.

Thanks, Vlad

Re: Incremental repairs in 3.0

[Vlad]

Thanks for answer!

>It may still be a good idea to manually migrate if you have a sizable amount 
>of dataNo, it would be brand new ;-) 3.0 cluster 

 

On Tuesday, June 21, 2016 1:21 AM, Bryan Cheng <br...@blockcypher.com> 
wrote:
 

 Sorry, meant to say "therefore manual migration procedure should be 
UNnecessary"
On Mon, Jun 20, 2016 at 3:21 PM, Bryan Cheng <br...@blockcypher.com> wrote:

I don't use 3.x so hopefully someone with operational experience can chime in, 
however my understanding is: 1) Incremental repairs should be the default in 
the 3.x release branch and 2) sstable repairedAt is now properly set in all 
sstables as of 2.2.x for standard repairs and therefore manual migration 
procedure should be necessary. It may still be a good idea to manually migrate 
if you have a sizable amount of data and are using LCS as anticompaction is 
rather painful.
On Sun, Jun 19, 2016 at 6:37 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hi,
assuming I have new, empty Cassandra cluster, how should I start using 
incremental repairs? Is incremental repair is default now (as I don't see -inc 
option in nodetool) and nothing is needed to use it, or should we perform 
migration procedure anyway? And what happens to new column families?
Regards.






   

Incremental repairs in 3.0

[Vlad]

Hi,
assuming I have new, empty Cassandra cluster, how should I start using 
incremental repairs? Is incremental repair is default now (as I don't see -inc 
option in nodetool) and nothing is needed to use it, or should we perform 
migration procedure anyway? And what happens to new column families?
Regards.

Choosing production version

[Vlad]

Before switching to tick-tock scheme one could choose latest previous x.y.z 
release, i.e. previous x.y with latest z to ensure maximum maturity and 
stability.
Now obviously odd bug-fixes releases are preferable, but actually for even x.y 
(3.2, 3.4, etc.) only single bug fix release will be issued (may be besides 
urgent critical and security fixes). Thus currently there are no "stable" 
version, and odd numbered releases constantly accumulate new features from even 
versions.
Just now 3.0.z is available, but what to take in future: latest "odd", or 
better previous "odds", to skip latest features and regression problem and to 
ensure no critical bugs found so far. But from other side previous "odds" have 
no latest fixes.
So what is general production choosing recommendation now?
Regards, Vlad

Re: Commit log size vs memtable total size

[Vlad]

Tyler, thanks for explanation!
So commit segment can contain both data from flushed table A and non-flushed 
table B.How is it replayed on start up? Does C* skip portions belonging to 
table A that already were written to SSTable?
Regards, Vlad
 

On Tuesday, March 1, 2016 11:37 PM, Tyler Hobbs <ty...@datastax.com> wrote:
 

 
On Tue, Mar 1, 2016 at 6:13 AM, Vlad <qa23d-...@yahoo.com> wrote:

So commit log can't keep more than memtable size, why is difference in commit 
log and memtables sizes?

In order to purge a commitlog segment, all memtables that contain data from 
that segment must be flushed to disk.

Suppose you have two tables:
 - table A has extremely high throughput
 - table B has low throughput

Every commitlog segment will have a mixture of writes for table A and table B.  
The memtable for table A will fill up rapidly and will be flushed frequently.  
The memtable for table B will slowly filly up, and will not be flushed often.  
Since table B's memtable isn't flushed, none of the commit log segments can 
purged/recycled.  Once the commitlog hits its size limit, it will force a flush 
of table B.

This behavior is good, because it allows table B to be flushed in large chunks 
instead of hundreds of tiny sstables.  If the commitlog space were equal to the 
memtable space, Cassandra would have to force a flush of table B's memtable 
approximately every time table A is flushed, despite being much smaller.

To summarize: if you use more than one table, it makes sense to have a larger 
space for commitlog segments.

-- 
Tyler Hobbs
DataStax


  

Re: Practical limit on number of column families

[Vlad]

>If your Jira search fu is strong enoughAnd it is! )

>you should be able to find it yourselfAnd I did! )
I see that this issue originates to problem with Java GC's design, but 
according to date it was Java 6 time. Now we have J8 with new  GC mechanism.
Is this problem still exists with J8? Any chances to use original method to 
reduce overhead and "be happy with the results"?
Regards, Vlad
 

On Tuesday, March 1, 2016 4:07 PM, Jack Krupansky 
<jack.krupan...@gmail.com> wrote:
 

 I'll defer to one of the senior committers as to whether they want that 
information disseminated any further than it already is. It was intentionally 
not documented since it is not recommended. If your Jira search fu is strong 
enough you should be able to find it yourself, but again, its use is strongly 
not recommended.
As the Jira notes, "having more than dozens or hundreds of tables defined is 
almost certainly a Bad Idea."
"Bad Idea" means not good. As in don't go there. And if you do, don't expect 
such a mis-adventure to be supported by the community.
-- Jack Krupansky
On Tue, Mar 1, 2016 at 8:39 AM, Vlad <qa23d-...@yahoo.com> wrote:

Hi Jack,
>you can reduce the overhead per table  an undocumented Jira Can you please 
>point to this Jira number?
 
>it is strongly not recommendedWhat is consequences of this (besides 
>performance degradation, if any)?
Thanks.


On Tuesday, March 1, 2016 7:23 AM, Jack Krupansky 
<jack.krupan...@gmail.com> wrote:
 

 3,000 entries? What's an "entry"? Do you mean row, column, or... what?

You are using the obsolete terminology of CQL2 and Thrift - column family. With 
CQL3 you should be creating "tables". The practical recommendation of an upper 
limit of a few hundred tables across all key spaces remains.
Technically you can go higher and technically you can reduce the overhead per 
table (an undocumented Jira - intentionally undocumented since it is strongly 
not recommended), but... it is unlikely that you will be happy with the results.
What is the nature of the use case?
You basically have two choices: an additional cluster column to distinguish 
categories of table, or separate clusters for each few hundred of tables.

-- Jack Krupansky
On Mon, Feb 29, 2016 at 12:30 PM, Fernando Jimenez 
<fernando.jime...@wealth-port.com> wrote:

Hi all
I have a use case for Cassandra that would require creating a large number of 
column families. I have found references to early versions of Cassandra where 
each column family would require a fixed amount of memory on all nodes, 
effectively imposing an upper limit on the total number of CFs. I have also 
seen rumblings that this may have been fixed in later versions.
To put the question to rest, I have setup a DSE sandbox and created some code 
to generate column families populated with 3,000 entries each.
Unfortunately I have now hit this issue: 
https://issues.apache.org/jira/browse/CASSANDRA-9291
So I will have to retest against Cassandra 3.0 instead
However, I would like to understand the limitations regarding creation of 
column families. 
 * Is there a practical upper limit?  * is this a fixed limit, or does it scale 
as more nodes are added into the cluster?  * Is there a difference between one 
keyspace with thousands of column families, vs thousands of keyspaces with only 
a few column families each?
I haven’t found any hard evidence/documentation to help me here, but if you can 
point me in the right direction, I will oblige and RTFM away.
Many thanks for your help!
CheersFJ






   



  

Re: Practical limit on number of column families

[Vlad]

Hi Jack,
>you can reduce the overhead per table  an undocumented Jira Can you please 
>point to this Jira number?
 
>it is strongly not recommendedWhat is consequences of this (besides 
>performance degradation, if any)?
Thanks.


On Tuesday, March 1, 2016 7:23 AM, Jack Krupansky 
 wrote:
 

 3,000 entries? What's an "entry"? Do you mean row, column, or... what?

You are using the obsolete terminology of CQL2 and Thrift - column family. With 
CQL3 you should be creating "tables". The practical recommendation of an upper 
limit of a few hundred tables across all key spaces remains.
Technically you can go higher and technically you can reduce the overhead per 
table (an undocumented Jira - intentionally undocumented since it is strongly 
not recommended), but... it is unlikely that you will be happy with the results.
What is the nature of the use case?
You basically have two choices: an additional cluster column to distinguish 
categories of table, or separate clusters for each few hundred of tables.

-- Jack Krupansky
On Mon, Feb 29, 2016 at 12:30 PM, Fernando Jimenez 
 wrote:

Hi all
I have a use case for Cassandra that would require creating a large number of 
column families. I have found references to early versions of Cassandra where 
each column family would require a fixed amount of memory on all nodes, 
effectively imposing an upper limit on the total number of CFs. I have also 
seen rumblings that this may have been fixed in later versions.
To put the question to rest, I have setup a DSE sandbox and created some code 
to generate column families populated with 3,000 entries each.
Unfortunately I have now hit this issue: 
https://issues.apache.org/jira/browse/CASSANDRA-9291
So I will have to retest against Cassandra 3.0 instead
However, I would like to understand the limitations regarding creation of 
column families. 
 * Is there a practical upper limit?  * is this a fixed limit, or does it scale 
as more nodes are added into the cluster?  * Is there a difference between one 
keyspace with thousands of column families, vs thousands of keyspaces with only 
a few column families each?
I haven’t found any hard evidence/documentation to help me here, but if you can 
point me in the right direction, I will oblige and RTFM away.
Many thanks for your help!
CheersFJ






  

Commit log size vs memtable total size

[Vlad]

Hi,there are following parameters in casansdra.yaml:
memtable_total_space_in_mb (1/4 of heap, e.g. 512MB)- Specifies the total 
memory used for all memtables on a node.
commitlog_total_space_in_mb (8GB) - Total space used for commit logs. If the 
used space goes above this value, Cassandra rounds up to the next nearest 
segment multiple and flushes memtables to disk for the  oldest commitlog 
segments, removing those log segments.
My question is what is meaning of commit log size being much more than 
memtables size.
>From manual: "Cassandra flushes memtables to disk, creating SSTables when the 
>commit log space threshold has been exceeded.", but as far as I understand 
>memtables are also flushed when too much memtables are used and anyway 
>unflashed size can't be more than memtable size in memory.  So commit log 
>can't keep more than memtable size, why is difference in commit log and 
>memtables sizes?

Regards, Vlad

Re: Cassandra C client implementation

[Vlad Paiu]

Hello,

Sorry, wrong link in the previous email. Proper link is
http://svn.apache.org/viewvc/thrift/trunk/lib/c_glib/test/

Regards,

Vlad Paiu
OpenSIPS Developer


On 12/15/2011 08:35 PM, Vlad Paiu wrote:

Hello,

While digging more for this I've found these :

http://svn.apache.org/viewvc/thrift/lib/c_glib/test/

Which shows how to create the TSocket and TTransport structures, very similar 
to the way it's done in C++.

Now I'm stuck on how to create the actual connection to the Cassandra server. 
It should be a function generated by the Cassandra thrift interface, but I 
can't seem to find the proper one.
Any help would be very much appreciated.

Regards,
Vlad

Mina Naguibmina.nag...@bloomdigital.com  wrote:


Hi Vlad

I'm the author of libcassie.

For what it's worth, it's in production where I work, consuming a heavily-used 
cassandra 0.7.9 cluster.

We do have plans to upgrade the cluster to 1.x, to benefit from all the 
improvements, CQL, etc... but that includes revising all our clients (across 
several programming languages).

So, it's definitely on my todo list to address our C clients by either 
upgrading libcassie, or possibly completely rewriting it.

Currently it's a wrapper around the C++ parent project libcassandra.  I haven't 
been fond of having that many layered abstractions, and the thrift Glib2 
interface has definitely piqued my interest, so I'm leaning towards a complete 
rewrite.

While we're at it, it would also be nice to have features like asynchronous 
modes for popular event loops, connection pooling, etc.

Unfortunately, I have no milestones set for any of this, nor the time 
(currently) to experiment and proof-of-concept it.

I'd be curious to hear from other C hackers whether they've experimented with the thrift 
Glib2 interface and gotten a hello world to work against cassandra 1.x.  
Perhaps there's room for some code sharing/collaboration on a new library to supersede 
the existing libcassie+libcassandra.


On 2011-12-14, at 5:16 PM, Vlad Paiu wrote:


Hello Eric,

We have that, thanks alot for the contribution.
The idea is to not play around with including C++ code in a C app, if there's 
an alternative ( the thrift g_libc ).

Unfortunately, since thrift does not generate a skeleton for the glibc code, I 
don't know how to find out what the API functions are called, and guessing them 
is not going that good :)

I'll wait a little longer  see if anybody can help with the C thrift, or at 
least tell me it's not working. :)

Regards,
Vlad

Eric Tammeeta...@gmail.com  wrote:


On 12/14/2011 04:18 PM, Vlad Paiu wrote:

Hi,

Just tried libcassie and seems it's not compatible with latest cassandra, as 
even simple inserts and fetches fail with InvalidRequestException...

So can anybody please provide a very simple example in C for connecting   
fetching columns with thrift ?

Regards,
Vlad

Vlad Paiuvladp...@opensips.org   wrote:


Vlad,

We have written a specific cassandra db module for usrloc with opensips
and have open sourced it on github.  We use the thrift generated c++
bindings and extern stuff to c.  I spoke to bogdan about this a while
ago, and gave him the github link, but here it is for your reference
https://github.com/junction/db_jnctn_usrloc

Hopefully that helps.  I idle in #opensips too,  just ask about
cassandra in there and I'll probably see it.

- Eric Tamme

Re: Cassandra C client implementation

[Vlad Paiu]

Hi,

I've also decided to give the C++ Thrift a try, but I can't seem to 
compile the simple examples from

http://wiki.apache.org/cassandra/ThriftExamples .

I get lots of errors like :
/usr/local/include/thrift/transport/TTransport.h:34:1: error: 
‘uint32_t’ does not name a type
/usr/local/include/thrift/transport/TTransport.h:56:1: error: 
expected unqualified-id before ‘class’
/usr/local/include/thrift/transport/TTransport.h:262:29: error: 
‘TTransport’ was not declared in this scope
/usr/local/include/thrift/transport/TTransport.h:262:39: error: 
template argument 1 is invalid
/usr/local/include/thrift/transport/TTransport.h:262:72: error: 
‘TTransport’ was not declared in this scope
/usr/local/include/thrift/transport/TTransport.h:262:82: error: 
template argument 1 is invalid


Thrift version is 0.8, installed from sources, Cassandra version in 1.0.6.

Any ideas ?

Regards,

Vlad Paiu
OpenSIPS Developer


On 12/16/2011 11:02 AM, Vlad Paiu wrote:

Hello,

Sorry, wrong link in the previous email. Proper link is
http://svn.apache.org/viewvc/thrift/trunk/lib/c_glib/test/

Regards,

Vlad Paiu
OpenSIPS Developer


On 12/15/2011 08:35 PM, Vlad Paiu wrote:

Hello,

While digging more for this I've found these :

http://svn.apache.org/viewvc/thrift/lib/c_glib/test/

Which shows how to create the TSocket and TTransport structures, very 
similar to the way it's done in C++.


Now I'm stuck on how to create the actual connection to the Cassandra 
server. It should be a function generated by the Cassandra thrift 
interface, but I can't seem to find the proper one.

Any help would be very much appreciated.

Regards,
Vlad

Mina Naguibmina.nag...@bloomdigital.com  wrote:


Hi Vlad

I'm the author of libcassie.

For what it's worth, it's in production where I work, consuming a 
heavily-used cassandra 0.7.9 cluster.


We do have plans to upgrade the cluster to 1.x, to benefit from all 
the improvements, CQL, etc... but that includes revising all our 
clients (across several programming languages).


So, it's definitely on my todo list to address our C clients by 
either upgrading libcassie, or possibly completely rewriting it.


Currently it's a wrapper around the C++ parent project 
libcassandra.  I haven't been fond of having that many layered 
abstractions, and the thrift Glib2 interface has definitely piqued 
my interest, so I'm leaning towards a complete rewrite.


While we're at it, it would also be nice to have features like 
asynchronous modes for popular event loops, connection pooling, etc.


Unfortunately, I have no milestones set for any of this, nor the 
time (currently) to experiment and proof-of-concept it.


I'd be curious to hear from other C hackers whether they've 
experimented with the thrift Glib2 interface and gotten a hello 
world to work against cassandra 1.x.  Perhaps there's room for some 
code sharing/collaboration on a new library to supersede the 
existing libcassie+libcassandra.



On 2011-12-14, at 5:16 PM, Vlad Paiu wrote:


Hello Eric,

We have that, thanks alot for the contribution.
The idea is to not play around with including C++ code in a C app, 
if there's an alternative ( the thrift g_libc ).


Unfortunately, since thrift does not generate a skeleton for the 
glibc code, I don't know how to find out what the API functions are 
called, and guessing them is not going that good :)


I'll wait a little longer  see if anybody can help with the C 
thrift, or at least tell me it's not working. :)


Regards,
Vlad

Eric Tammeeta...@gmail.com  wrote:


On 12/14/2011 04:18 PM, Vlad Paiu wrote:

Hi,

Just tried libcassie and seems it's not compatible with latest 
cassandra, as even simple inserts and fetches fail with 
InvalidRequestException...


So can anybody please provide a very simple example in C for 
connecting   fetching columns with thrift ?


Regards,
Vlad

Vlad Paiuvladp...@opensips.org   wrote:


Vlad,

We have written a specific cassandra db module for usrloc with 
opensips

and have open sourced it on github.  We use the thrift generated c++
bindings and extern stuff to c.  I spoke to bogdan about this a while
ago, and gave him the github link, but here it is for your reference
https://github.com/junction/db_jnctn_usrloc

Hopefully that helps.  I idle in #opensips too,  just ask about
cassandra in there and I'll probably see it.

- Eric Tamme

Re: Cassandra C client implementation

[Vlad Paiu]

Hello,

Congratulations on your work on libcassandra  libcassie.
I agree with you that too many abstractions are not a good thing, that's 
why I think thrift  glib are a much better way to go than thrift  cpp 
 libcassandra  libcassie.


I as well am looking for a very basic Thrift  glibc example for 
Cassandra, with no 'advanced' features like connection pooling, 
asynchronous stuff, etc.
Just a plain  simple connection, an insert and a column fetch that 
works with the latest 1.x Cassandra.

I think it would be a great starting point and we could move on from there.

Regards,

Vlad Paiu
OpenSIPS Developer


On 12/15/2011 03:53 AM, Mina Naguib wrote:

Hi Vlad

I'm the author of libcassie.

For what it's worth, it's in production where I work, consuming a heavily-used 
cassandra 0.7.9 cluster.

We do have plans to upgrade the cluster to 1.x, to benefit from all the 
improvements, CQL, etc... but that includes revising all our clients (across 
several programming languages).

So, it's definitely on my todo list to address our C clients by either 
upgrading libcassie, or possibly completely rewriting it.

Currently it's a wrapper around the C++ parent project libcassandra.  I haven't 
been fond of having that many layered abstractions, and the thrift Glib2 
interface has definitely piqued my interest, so I'm leaning towards a complete 
rewrite.

While we're at it, it would also be nice to have features like asynchronous 
modes for popular event loops, connection pooling, etc.

Unfortunately, I have no milestones set for any of this, nor the time 
(currently) to experiment and proof-of-concept it.

I'd be curious to hear from other C hackers whether they've experimented with the thrift 
Glib2 interface and gotten a hello world to work against cassandra 1.x.  
Perhaps there's room for some code sharing/collaboration on a new library to supersede 
the existing libcassie+libcassandra.


On 2011-12-14, at 5:16 PM, Vlad Paiu wrote:


Hello Eric,

We have that, thanks alot for the contribution.
The idea is to not play around with including C++ code in a C app, if there's 
an alternative ( the thrift g_libc ).

Unfortunately, since thrift does not generate a skeleton for the glibc code, I 
don't know how to find out what the API functions are called, and guessing them 
is not going that good :)

I'll wait a little longer  see if anybody can help with the C thrift, or at 
least tell me it's not working. :)

Regards,
Vlad

Eric Tammeeta...@gmail.com  wrote:


On 12/14/2011 04:18 PM, Vlad Paiu wrote:

Hi,

Just tried libcassie and seems it's not compatible with latest cassandra, as 
even simple inserts and fetches fail with InvalidRequestException...

So can anybody please provide a very simple example in C for connecting   
fetching columns with thrift ?

Regards,
Vlad

Vlad Paiuvladp...@opensips.org   wrote:


Vlad,

We have written a specific cassandra db module for usrloc with opensips
and have open sourced it on github.  We use the thrift generated c++
bindings and extern stuff to c.  I spoke to bogdan about this a while
ago, and gave him the github link, but here it is for your reference
https://github.com/junction/db_jnctn_usrloc

Hopefully that helps.  I idle in #opensips too,  just ask about
cassandra in there and I'll probably see it.

- Eric Tamme

Re: Cassandra C client implementation

[Vlad Paiu]

Hello,

While digging more for this I've found these :

http://svn.apache.org/viewvc/thrift/lib/c_glib/test/

Which shows how to create the TSocket and TTransport structures, very similar 
to the way it's done in C++.

Now I'm stuck on how to create the actual connection to the Cassandra server. 
It should be a function generated by the Cassandra thrift interface, but I 
can't seem to find the proper one.
Any help would be very much appreciated.

Regards,
Vlad

Mina Naguib mina.nag...@bloomdigital.com wrote:


Hi Vlad

I'm the author of libcassie.

For what it's worth, it's in production where I work, consuming a heavily-used 
cassandra 0.7.9 cluster.

We do have plans to upgrade the cluster to 1.x, to benefit from all the 
improvements, CQL, etc... but that includes revising all our clients (across 
several programming languages).

So, it's definitely on my todo list to address our C clients by either 
upgrading libcassie, or possibly completely rewriting it.

Currently it's a wrapper around the C++ parent project libcassandra.  I 
haven't been fond of having that many layered abstractions, and the thrift 
Glib2 interface has definitely piqued my interest, so I'm leaning towards a 
complete rewrite.

While we're at it, it would also be nice to have features like asynchronous 
modes for popular event loops, connection pooling, etc.

Unfortunately, I have no milestones set for any of this, nor the time 
(currently) to experiment and proof-of-concept it.

I'd be curious to hear from other C hackers whether they've experimented with 
the thrift Glib2 interface and gotten a hello world to work against 
cassandra 1.x.  Perhaps there's room for some code sharing/collaboration on a 
new library to supersede the existing libcassie+libcassandra.


On 2011-12-14, at 5:16 PM, Vlad Paiu wrote:

 Hello Eric,
 
 We have that, thanks alot for the contribution.
 The idea is to not play around with including C++ code in a C app, if 
 there's an alternative ( the thrift g_libc ).
 
 Unfortunately, since thrift does not generate a skeleton for the glibc code, 
 I don't know how to find out what the API functions are called, and guessing 
 them is not going that good :)
 
 I'll wait a little longer  see if anybody can help with the C thrift, or at 
 least tell me it's not working. :)
 
 Regards,
 Vlad
 
 Eric Tamme eta...@gmail.com wrote:
 
 On 12/14/2011 04:18 PM, Vlad Paiu wrote:
 Hi,
 
 Just tried libcassie and seems it's not compatible with latest cassandra, 
 as even simple inserts and fetches fail with InvalidRequestException...
 
 So can anybody please provide a very simple example in C for connecting  
 fetching columns with thrift ?
 
 Regards,
 Vlad
 
 Vlad Paiuvladp...@opensips.org  wrote:
 
 
 Vlad,
 
 We have written a specific cassandra db module for usrloc with opensips 
 and have open sourced it on github.  We use the thrift generated c++ 
 bindings and extern stuff to c.  I spoke to bogdan about this a while 
 ago, and gave him the github link, but here it is for your reference   
 https://github.com/junction/db_jnctn_usrloc
 
 Hopefully that helps.  I idle in #opensips too,  just ask about 
 cassandra in there and I'll probably see it.
 
 - Eric Tamme
 

Cassandra C client implementation

[Vlad Paiu]

Hello,

I am trying to integrate some Cassandra related ops ( insert, get, etc ) into 
an application written entirelly in C, so C++ is not an option.

Is there any C client library for cassandra ?

 I have also tried to generate thrift glibc code for Cassandra, but on 
wiki.apache.org/cassandra/ThriftExamples I cannot find an example for C. 

Can anybody suggest a C client library for Cassandra or provide some working 
examples for Thrift in C ?

Thanks and Regards,
Vlad

Re: Cassandra C client implementation

[Vlad Paiu]

Hello,

Thanks for your answer.
Unfortunately libcassandra is C++ , I'm looking for something written in ANSI C.

I've searched alot and my guess is glibc thrift is my only option, but I could 
not find even one example onto how to make a connection  some queries to 
Cassandra using glibc thrift.
Does anyone have experience/some examples for this ?

Regards,
Vlad


i...@iyyang.com wrote:

BTW please use 
https://github.com/eyealike/libcassandra


Best Regards,
Yi Steve Yang
~~~
+1-401-441-5086
+86-13910771510

Sent via BlackBerry® from China Mobile

-Original Message-
From: i...@iyyang.com
Date: Wed, 14 Dec 2011 15:52:56 
To: user@cassandra.apache.org
Reply-To: i...@iyyang.com
Subject: Re: Cassandra C client implementation

Try libcassandra, but it doesn't support connection pooling

--Original Message--
From: Vlad Paiu
To: user@cassandra.apache.org
ReplyTo: user@cassandra.apache.org
Subject: Cassandra C client implementation
Sent: Dec 14, 2011 11:11 PM

Hello,

I am trying to integrate some Cassandra related ops ( insert, get, etc ) into 
an application written entirelly in C, so C++ is not an option.

Is there any C client library for cassandra ?

 I have also tried to generate thrift glibc code for Cassandra, but on 
 wiki.apache.org/cassandra/ThriftExamples I cannot find an example for C. 

Can anybody suggest a C client library for Cassandra or provide some working 
examples for Thrift in C ?

Thanks and Regards,
Vlad
Best Regards,
Yi Steve Yang
~~~
+1-401-441-5086
+86-13910771510

Sent via BlackBerry® from China Mobile

Re: Cassandra C client implementation

[Vlad Paiu]

Hello,

Thanks very much for your suggestions.
Libcassie seems nice but doesn't seem like it's actively maintained and i'm not 
sure if it's compatible with latest Cassandra versions. Will give it a try 
though.

I was looking through the generated thrift .c files and I can't seem to find 
what function to call to init a connection to a Cassandra instance. Any ideas ?

Thanks and Regards,
Vlad

Jeremiah Jordan jeremiah.jor...@morningstar.com wrote:

If you are OK linking to a C++ based library you can look at:
https://github.com/minaguib/libcassandra/tree/kickstart-libcassie-0.7/libcassie
It is wrapper code around libcassandra which exports a C++ interface.
If you look at the function names etc in the other languages, just use 
the similar functions from the c_glib thrift...
If you are going to mess with using the c_glib thrift, make sure to 
check out the JIRA for it, it is new and has some issues...
https://issues.apache.org/jira/browse/THRIFT/component/12313854


On 12/14/2011 09:11 AM, Vlad Paiu wrote:
 Hello,

 I am trying to integrate some Cassandra related ops ( insert, get, etc ) 
 into an application written entirelly in C, so C++ is not an option.

 Is there any C client library for cassandra ?

   I have also tried to generate thrift glibc code for Cassandra, but on 
 wiki.apache.org/cassandra/ThriftExamples I cannot find an example for C.

 Can anybody suggest a C client library for Cassandra or provide some working 
 examples for Thrift in C ?

 Thanks and Regards,
 Vlad

Re: Cassandra C client implementation

[Vlad Paiu]

Hi,

Just tried libcassie and seems it's not compatible with latest cassandra, as 
even simple inserts and fetches fail with InvalidRequestException...

So can anybody please provide a very simple example in C for connecting  
fetching columns with thrift ?

Regards,
Vlad

Vlad Paiu vladp...@opensips.org wrote:

Hello,

Thanks very much for your suggestions.
Libcassie seems nice but doesn't seem like it's actively maintained and i'm 
not sure if it's compatible with latest Cassandra versions. Will give it a try 
though.

I was looking through the generated thrift .c files and I can't seem to find 
what function to call to init a connection to a Cassandra instance. Any ideas ?

Thanks and Regards,
Vlad

Jeremiah Jordan jeremiah.jor...@morningstar.com wrote:

If you are OK linking to a C++ based library you can look at:
https://github.com/minaguib/libcassandra/tree/kickstart-libcassie-0.7/libcassie
It is wrapper code around libcassandra which exports a C++ interface.
If you look at the function names etc in the other languages, just use 
the similar functions from the c_glib thrift...
If you are going to mess with using the c_glib thrift, make sure to 
check out the JIRA for it, it is new and has some issues...
https://issues.apache.org/jira/browse/THRIFT/component/12313854


On 12/14/2011 09:11 AM, Vlad Paiu wrote:
 Hello,

 I am trying to integrate some Cassandra related ops ( insert, get, etc ) 
 into an application written entirelly in C, so C++ is not an option.

 Is there any C client library for cassandra ?

   I have also tried to generate thrift glibc code for Cassandra, but on 
 wiki.apache.org/cassandra/ThriftExamples I cannot find an example for C.

 Can anybody suggest a C client library for Cassandra or provide some 
 working examples for Thrift in C ?

 Thanks and Regards,
 Vlad

Re: Cassandra C client implementation

[Vlad Paiu]

Hello Eric,

We have that, thanks alot for the contribution.
The idea is to not play around with including C++ code in a C app, if there's 
an alternative ( the thrift g_libc ).

Unfortunately, since thrift does not generate a skeleton for the glibc code, I 
don't know how to find out what the API functions are called, and guessing them 
is not going that good :)

I'll wait a little longer  see if anybody can help with the C thrift, or at 
least tell me it's not working. :)

Regards,
Vlad

Eric Tamme eta...@gmail.com wrote:

On 12/14/2011 04:18 PM, Vlad Paiu wrote:
 Hi,

 Just tried libcassie and seems it's not compatible with latest cassandra, as 
 even simple inserts and fetches fail with InvalidRequestException...

 So can anybody please provide a very simple example in C for connecting  
 fetching columns with thrift ?

 Regards,
 Vlad

 Vlad Paiuvladp...@opensips.org  wrote:


Vlad,

We have written a specific cassandra db module for usrloc with opensips 
and have open sourced it on github.  We use the thrift generated c++ 
bindings and extern stuff to c.  I spoke to bogdan about this a while 
ago, and gave him the github link, but here it is for your reference   
https://github.com/junction/db_jnctn_usrloc

Hopefully that helps.  I idle in #opensips too,  just ask about 
cassandra in there and I'll probably see it.

- Eric Tamme

Re: Cassandra Counters and TTL

[Vlad Paiu]

Hello,

Thanks for your answer. See my reply in-line.

On 11/04/2011 01:46 PM, Amit Chavan wrote:


Answers inline.

On Fri, Nov 4, 2011 at 4:59 PM, Vlad Paiu vladp...@opensips.org 
mailto:vladp...@opensips.org wrote:


Hello,

I'm a new user of Cassandra and I think it's great.
Still, while developing my APP using Cassandra, I got stuck with
some things and I'm not really sure that Cassandra can handle them
at the moment.

So, first of all, does Cassandra allow for Counters and regular
Keys to be located in the same ColumnFamily ?

What do you mean when you say regular Keys? If you are hinting at 
columns apart from counters, then the answer is *no*: only counters 
can exist in a CounterColumnFamily and other column families cannot 
hold counters.

Yes, this is what I was asking. Thanks for the answer.



Secondly, is there any way to dynamically set the TTL for a key ?
In the sense that I have a key, I initially set it with no TTL,
but after a while I decide that it should expire in 100 seconds.
Can Cassandra do this ?

TTL is not for one key, it is for one column.


When I was saying 'Key' I actually meant to say column. Seems I'm not 
yet very acquainted with Cassandra terminology. So in the end, can you 
dynamically alter the TTL of a Column ?




3. Can counters have a TTL ?

No. Currently, counters do not (or if I am correct - cannot) have TTL.



Ok. Any info if this will be implemented anytime soon ?


4. Is there any way to atomically reset a counter ? I read on the
website that the only way to do it is read the variable value, and
then set it to -value, which seems rather bogus to me.

I think that is the only way to reset a counter. I would like to know 
if there is another way.


Ok then, waiting for someone to confirm. It's bad that you cannot 
atomically reset a counter value, as a two-way resetting might lead to 
undetermined behaviour.


Also, can I set the counter to a specific value, without keeping state 
on the client ? For example, if the client does not know the current 
counter value is 3. Can it set the counter value to 10, without first 
getting the counter value, and then incrementing by 7 ?


Background: I am using Cassandra since the past two months. Hope the 
community corrects me if I am wrong.



Regards,

-- 
Vlad Paiu

OpenSIPS Developer




--
Regards
Amit S. Chavan





Regards,

Vlad Paiu
OpenSIPS Developer

Cassandra Counters and TTL

[Vlad Paiu]

Hello,

I'm a new user of Cassandra and I think it's great.
Still, while developing my APP using Cassandra, I got stuck with some 
things and I'm not really sure that Cassandra can handle them at the 
moment.


So, first of all, does Cassandra allow for Counters and regular Keys to 
be located in the same ColumnFamily ?


Secondly, is there any way to dynamically set the TTL for a key ? In the 
sense that I have a key, I initially set it with no TTL, but after a 
while I decide that it should expire in 100 seconds. Can Cassandra do 
this ?


3. Can counters have a TTL ?

4. Is there any way to atomically reset a counter ? I read on the 
website that the only way to do it is read the variable value, and then 
set it to -value, which seems rather bogus to me.


Regards,

--
Vlad Paiu
OpenSIPS Developer