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From Ondřej Černoš <cern...@gmail.com>
Subject Re: nodetool status inconsistencies, repair performance and system keyspace compactions
Date Thu, 04 Apr 2013 12:12:23 GMT
Hi,

most has been resolved - the failed to uncompress error was really a
bug in cassandra (see
https://issues.apache.org/jira/browse/CASSANDRA-5391) and the problem
with different load reporting is a change between 1.2.1 (reports 100%
for 3 replicas/3 nodes/2 DCs setup I have) and 1.2.3 which reports the
fraction. Is this correct?

Anyway, the nodetool repair still takes ages to finish, considering
only megabytes of not changing data are involved in my test:

[root@host:/etc/puppet] nodetool repair ks
[2013-04-04 13:26:46,618] Starting repair command #1, repairing 1536
ranges for keyspace ks
[2013-04-04 13:47:17,007] Repair session
88ebc700-9d1a-11e2-a0a1-05b94e1385c7 for range
(-2270395505556181001,-2268004533044804266] finished
...
[2013-04-04 13:47:17,063] Repair session
65d31180-9d1d-11e2-a0a1-05b94e1385c7 for range
(1069254279177813908,1070290707448386360] finished
[2013-04-04 13:47:17,063] Repair command #1 finished

This is the status before the repair (by the way, after the datacenter
has been bootstrapped from the remote one):

[root@host:/etc/puppet] nodetool status
Datacenter: us-east
===================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address                   Load       Tokens  Owns   Host ID
                                    Rack
UN  xxx.xxx.xxx.xxx    5.74 MB    256     17.1%
06ff8328-32a3-4196-a31f-1e0f608d0638  1d
UN  xxx.xxx.xxx.xxx    5.73 MB    256     15.3%
7a96bf16-e268-433a-9912-a0cf1668184e  1d
UN  xxx.xxx.xxx.xxx    5.72 MB    256     17.5%
67a68a2a-12a8-459d-9d18-221426646e84  1d
Datacenter: na-dev
==================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address                  Load       Tokens  Owns   Host ID
                                       Rack
UN  xxx.xxx.xxx.xxx   5.74 MB    256     16.4%
eb86aaae-ef0d-40aa-9b74-2b9704c77c0a  cmp02
UN  xxx.xxx.xxx.xxx   5.74 MB    256     17.0%
cd24af74-7f6a-4eaa-814f-62474b4e4df1  cmp01
UN  xxx.xxx.xxx.xxx   5.74 MB    256     16.7%
1a55cfd4-bb30-4250-b868-a9ae13d81ae1  cmp05

Why does it take 20 minutes to finish? Fortunately the big number of
compactions I reported in the previous email was not triggered.

And is there a documentation where I could find the exact semantics of
repair when vnodes are used (and what -pr means in such a setup) and
when run in multiple datacenter setup? I still don't quite get it.

regards,
Ondřej Černoš


On Thu, Mar 28, 2013 at 3:30 AM, aaron morton <aaron@thelastpickle.com> wrote:
> During one of my tests - see this thread in this mailing list:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/java-io-IOException-FAILED-TO-UNCOMPRESS-5-exception-when-running-nodetool-rebuild-td7586494.html
>
> That thread has been updated, check the bug ondrej created.
>
> How will this perform in production with much bigger data if repair
> takes 25 minutes on 7MB and 11k compactions were triggered by the
> repair run?
>
> Seems a little odd.
> See what happens the next time you run repair.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 27/03/2013, at 2:36 AM, Ondřej Černoš <cernoso@gmail.com> wrote:
>
> Hi all,
>
> I have 2 DCs, 3 nodes each, RF:3, I use local quorum for both reads and
> writes.
>
> Currently I test various operational qualities of the setup.
>
> During one of my tests - see this thread in this mailing list:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/java-io-IOException-FAILED-TO-UNCOMPRESS-5-exception-when-running-nodetool-rebuild-td7586494.html
> - I ran into this situation:
>
> - all nodes have all data and agree on it:
>
> [user@host1-dc1:~] nodetool status
>
> Datacenter: na-prod
> ===================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address                        Load         Tokens  Owns
> (effective)  Host ID                                            Rack
> UN  XXX.XXX.XXX.XXX   7.74 MB    256     100.0%
> 0b1f1d79-52af-4d1b-a86d-bf4b65a05c49  cmp17
> UN  XXX.XXX.XXX.XXX   7.74 MB    256     100.0%
> 039f206e-da22-44b5-83bd-2513f96ddeac  cmp10
> UN  XXX.XXX.XXX.XXX   7.72 MB    256     100.0%
> 007097e9-17e6-43f7-8dfc-37b082a784c4  cmp11
> Datacenter: us-east
> ===================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address                        Load         Tokens  Owns
> (effective)  Host ID                                            Rack
> UN  XXX.XXX.XXX.XXX    7.73 MB    256     100.0%
> a336efae-8d9c-4562-8e2a-b766b479ecb4  1d
> UN  XXX.XXX.XXX.XXX    7.73 MB    256     100.0%
> ab1bbf0a-8ddc-4a12-a925-b119bd2de98e  1d
> UN  XXX.XXX.XXX.XXX     7.73 MB    256     100.0%
> f53fd294-16cc-497e-9613-347f07ac3850  1d
>
> - only one node disagrees:
>
> [user@host1-dc2:~] nodetool status
> Datacenter: us-east
> ===================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address                         Load       Tokens   Owns   Host ID
>                                              Rack
> UN  XXX.XXX.XXX.XXX    7.73 MB    256     17.6%
> a336efae-8d9c-4562-8e2a-b766b479ecb4  1d
> UN  XXX.XXX.XXX.XXX    7.75 MB    256     16.4%
> ab1bbf0a-8ddc-4a12-a925-b119bd2de98e  1d
> UN  XXX.XXX.XXX.XXX     7.73 MB    256     15.7%
> f53fd294-16cc-497e-9613-347f07ac3850  1d
> Datacenter: na-prod
> ===================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address                         Load       Tokens   Owns   Host ID
>                                              Rack
> UN  XXX.XXX.XXX.XXX   7.74 MB    256     16.9%
> 0b1f1d79-52af-4d1b-a86d-bf4b65a05c49  cmp17
> UN  XXX.XXX.XXX.XXX   7.72 MB    256     17.1%
> 007097e9-17e6-43f7-8dfc-37b082a784c4  cmp11
> UN  XXX.XXX.XXX.XXX   7.73 MB    256     16.3%
> 039f206e-da22-44b5-83bd-2513f96ddeac  cmp10
>
> I tried to rebuild the node from scratch, repair the node, no results.
> Still the same owns stats.
>
> The cluster is built from cassandra 1.2.3 and uses vnodes.
>
>
> On the related note: the data size, as you can see, is really small.
> The cluster was created by setting up the us-east datacenter,
> populating it with the dataset, then building the na-prod datacenter
> and running nodetool rebuild us-east. When I tried to run nodetool
> repair it took 25 minutes to finish, on this small dataset. Is this
> ok?
>
> One other think I notices is the amount of compactions on the system
> keyspace:
>
> /.../system/schema_columnfamilies/system-schema_columnfamilies-ib-11694-TOC.txt
> /.../system/schema_columnfamilies/system-schema_columnfamilies-ib-11693-Statistics.db
>
> This is just after running the repair. Is this ok, considering the
> dataset is 7MB and during the repair no operations were running
> against the database, neither read, nor write, nothing?
>
> How will this perform in production with much bigger data if repair
> takes 25 minutes on 7MB and 11k compactions were triggered by the
> repair run?
>
> regards,
>
> Ondrej Cernos
>
>

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