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From Jayadev Jayaraman <jdisal...@gmail.com>
Subject Re: Cassandra 1.2.9 cluster with vnodes is heavily unbalanced.
Date Fri, 20 Sep 2013 16:24:37 GMT
As a follow-up, is operating a Cassandra cluster with machines on multiple
racks and vnodes bound to cause load imbalance ? Shouldn't token-ranges
assigned to individual machines via their vnodes be approximately balanced
? We're otherwise unable to explain why this imbalance occurs. ( it
shouldn't be the fault of the Murmur3 partitioner which guarantees a
uniform distribution of keys across token-ranges according to the doc. )


On Thu, Sep 19, 2013 at 8:56 PM, Jayadev Jayaraman <jdisalive@gmail.com>wrote:

> We're using NetworkTopologyStrategy for our placement_strategy and our
> primary motivation for placing nodes on more than 1 rack is to prevent
> showstoppers caused by localized faults leading to multiple EC2 instances
> in the same availability zone (rack) becoming unreachable (which we have
> encountered before).
>
> I've attached the output of "nodetool ring" here.
>
>
> On Thu, Sep 19, 2013 at 8:35 PM, Mohit Anchlia <mohitanchlia@gmail.com>wrote:
>
>> Other thing I noticed is that you are using mutiple RACKS and that might
>> be contributing factor to it. However, I am not sure.
>>
>> Can you paste the output of nodetool cfstats and ring? Is it possible to
>> run the same test but keeping all the nodes in one rack?
>>
>> I think you should open a JIRA if you are able to reproduce this.
>>
>> On Thu, Sep 19, 2013 at 4:41 PM, Jayadev Jayaraman <jdisalive@gmail.com>wrote:
>>
>>> We ran nodetool repair on all nodes for all Keyspaces / CFs, restarted
>>> cassandra and this is what we get for nodetool status :
>>>
>>> bin/nodetool -h localhost status
>>> Datacenter: us-east
>>> ===================
>>> Status=Up/Down
>>> |/ State=Normal/Leaving/Joining/Moving
>>> --  Address         Load       Tokens  Owns (effective)  Host ID
>>>                       Rack
>>> UN  10.238.133.174  885.36 MB  256     8.4%
>>>  e41d8863-ce37-4d5c-a428-bfacea432a35  1a
>>> UN  10.238.133.97   468.66 MB  256     7.7%
>>>  1bf42b5e-4aed-4b06-bdb3-65a78823b547  1a
>>> UN  10.151.86.146   1.08 GB    256     8.0%
>>>  8952645d-4a27-4670-afb2-65061c205734  1a
>>> UN  10.138.10.9     941.44 MB  256     8.6%
>>>  25ccea82-49d2-43d9-830c-b9c9cee026ec  1a
>>> UN  10.87.87.240    99.69 MB   256     8.6%
>>>  ea066827-83bc-458c-83e8-bd15b7fc783c  1b
>>> UN  10.93.5.157     87.44 MB   256     7.6%
>>>  4ab9111c-39b4-4d15-9401-359d9d853c16  1b
>>> UN  10.238.137.250  561.42 MB  256     7.8%
>>>  84301648-afff-4f06-aa0b-4be421e0d08f  1a
>>> UN  10.92.231.170   893.75 MB  256     9.3%
>>>  a18ce761-88a0-4407-bbd1-c867c4fecd1f  1b
>>> UN  10.138.2.20     31.89 MB   256     7.9%
>>>  a6d4672a-0915-4c64-ba47-9f190abbf951  1a
>>> UN  10.93.31.44     312.52 MB  256     7.8%
>>>  67a6c0a6-e89f-4f3e-b996-cdded1b94faf  1b
>>> UN  10.93.91.139    30.46 MB   256     8.1%
>>>  682dd848-7c7f-4ddb-a960-119cf6491aa1  1b
>>> UN  10.236.138.169  260.15 MB  256     9.1%
>>>  cbbf27b0-b53a-4530-bfdf-3764730b89d8  1a
>>> UN  10.137.7.90     38.45 MB   256     7.4%
>>>  17b79aa7-64fc-4e16-b96a-955b0aae9bb4  1a
>>> UN  10.93.77.166    867.15 MB  256     8.8%
>>>  9a821d1e-40e5-445d-b6b7-3cdd58bdb8cb  1b
>>> UN  10.120.249.140  863.98 MB  256     9.4%
>>>  e1fb69b0-8e66-4deb-9e72-f901d7a14e8a  1b
>>> UN  10.90.246.128   242.63 MB  256     8.4%
>>>  054911ec-969d-43d9-aea1-db445706e4d2  1b
>>> UN  10.123.95.248   171.51 MB  256     7.2%
>>>  a17deca1-9644-4520-9e62-ac66fc6fef60  1b
>>> UN  10.136.11.40    33.8 MB    256     8.5%
>>>  66be1173-b822-40b5-b650-cb38ae3c7a51  1a
>>> UN  10.87.90.42     38.01 MB   256     8.0%
>>>  dac0c6ea-56c6-44da-a4ec-6388f39ecba1  1b
>>> UN  10.87.75.147    579.29 MB  256     8.3%
>>>  ac060edf-dc48-44cf-a1b5-83c7a465f3c8  1b
>>> UN  10.151.49.88    151.06 MB  256     8.9%
>>>  57043573-ab1b-4e3c-8044-58376f7ce08f  1a
>>> UN  10.87.83.107    512.91 MB  256     8.3%
>>>  0019439b-9f8a-4965-91b8-7108bbb55593  1b
>>> UN  10.238.170.159  85.04 MB   256     9.4%
>>>  32ce322e-4f7c-46c7-a8ce-bd73cdd54684  1a
>>> UN  10.137.20.183   167.41 MB  256     8.4%
>>>  15951592-8ab2-473d-920a-da6e9d99507d  1a
>>>
>>> It doesn't seem to have changed by much. The loads are still highly
>>> uneven.
>>>
>>> As for the number of keys in each node's CFs : the largest node now
>>> has 5589120 keys for the column-family that had 6527744 keys before
>>> (load is now 1.08 GB as compares to 1.05 GB before), while the smallest
>>> node now has 71808 keys as compared to 3840 keys before (load is now
>>> 31.89 MB as compares to 1.12 MB before).
>>>
>>>
>>> On Thu, Sep 19, 2013 at 5:18 PM, Mohit Anchlia <mohitanchlia@gmail.com>wrote:
>>>
>>>> Can you run nodetool repair on all the nodes first and look at the keys?
>>>>
>>>>
>>>> On Thu, Sep 19, 2013 at 1:22 PM, Suruchi Deodhar <
>>>> suruchi.deodhar@generalsentiment.com> wrote:
>>>>
>>>>> Yes, the key distribution does vary across the nodes. For example, on
>>>>> the node with the highest data, Number of Keys (estimate) is 6527744
for a
>>>>> particular column family, whereas for the same column family on the node
>>>>> with least data, Number of Keys (estimate) = 3840.
>>>>>
>>>>> Is there a way to control this distribution by setting some parameter
>>>>> of cassandra.
>>>>>
>>>>> I am using the Murmur3 partitioner with NetworkTopologyStrategy.
>>>>>
>>>>> Thanks,
>>>>> Suruchi
>>>>>
>>>>>
>>>>>
>>>>> On Thu, Sep 19, 2013 at 3:59 PM, Mohit Anchlia <mohitanchlia@gmail.com
>>>>> > wrote:
>>>>>
>>>>>> Can you check cfstats to see number of keys per node?
>>>>>>
>>>>>>
>>>>>> On Thu, Sep 19, 2013 at 12:36 PM, Suruchi Deodhar <
>>>>>> suruchi.deodhar@generalsentiment.com> wrote:
>>>>>>
>>>>>>> Thanks for your replies. I wiped out my data from the cluster
and
>>>>>>> also cleared the commitlog before restarting it with num_tokens=256.
I then
>>>>>>> uploaded data using sstableloader.
>>>>>>>
>>>>>>> However, I am still not able to see a uniform distribution of
data
>>>>>>> across nodes of the clusters.
>>>>>>>
>>>>>>> The output of the bin/nodetool -h localhost status commands looks
>>>>>>> like follows. Some nodes have data as low as 1.12MB while some
have as high
>>>>>>> as 912.57 MB.
>>>>>>>
>>>>>>> Datacenter: us-east
>>>>>>> ===================
>>>>>>> Status=Up/Down
>>>>>>> |/ State=Normal/Leaving/Joining/Moving
>>>>>>> --  Address         Load       Tokens  Owns (effective)  Host
>>>>>>> ID                               Rack
>>>>>>> UN  10.238.133.174  856.66 MB  256     8.4%
>>>>>>> e41d8863-ce37-4d5c-a428-bfacea432a35  1a
>>>>>>> UN  10.238.133.97   439.02 MB  256     7.7%
>>>>>>> 1bf42b5e-4aed-4b06-bdb3-65a78823b547  1a
>>>>>>> UN  10.151.86.146   1.05 GB    256     8.0%
>>>>>>> 8952645d-4a27-4670-afb2-65061c205734  1a
>>>>>>> UN  10.138.10.9     912.57 MB  256     8.6%
>>>>>>> 25ccea82-49d2-43d9-830c-b9c9cee026ec  1a
>>>>>>> UN  10.87.87.240    70.85 MB   256     8.6%
>>>>>>> ea066827-83bc-458c-83e8-bd15b7fc783c  1b
>>>>>>> UN  10.93.5.157     60.56 MB   256     7.6%
>>>>>>> 4ab9111c-39b4-4d15-9401-359d9d853c16  1b
>>>>>>> UN  10.92.231.170   866.73 MB  256     9.3%
>>>>>>> a18ce761-88a0-4407-bbd1-c867c4fecd1f  1b
>>>>>>> UN  10.238.137.250  533.77 MB  256     7.8%
>>>>>>> 84301648-afff-4f06-aa0b-4be421e0d08f  1a
>>>>>>> UN  10.93.91.139    478.45 KB  256     8.1%
>>>>>>> 682dd848-7c7f-4ddb-a960-119cf6491aa1  1b
>>>>>>> UN  10.138.2.20     1.12 MB    256     7.9%
>>>>>>> a6d4672a-0915-4c64-ba47-9f190abbf951  1a
>>>>>>> UN  10.93.31.44     282.65 MB  256     7.8%
>>>>>>> 67a6c0a6-e89f-4f3e-b996-cdded1b94faf  1b
>>>>>>> UN  10.236.138.169  223.66 MB  256     9.1%
>>>>>>> cbbf27b0-b53a-4530-bfdf-3764730b89d8  1a
>>>>>>> UN  10.137.7.90     11.36 MB   256     7.4%
>>>>>>> 17b79aa7-64fc-4e16-b96a-955b0aae9bb4  1a
>>>>>>> UN  10.93.77.166    837.64 MB  256     8.8%
>>>>>>> 9a821d1e-40e5-445d-b6b7-3cdd58bdb8cb  1b
>>>>>>> UN  10.120.249.140  838.59 MB  256     9.4%
>>>>>>> e1fb69b0-8e66-4deb-9e72-f901d7a14e8a  1b
>>>>>>> UN  10.90.246.128   216.75 MB  256     8.4%
>>>>>>> 054911ec-969d-43d9-aea1-db445706e4d2  1b
>>>>>>> UN  10.123.95.248   147.1 MB   256     7.2%
>>>>>>> a17deca1-9644-4520-9e62-ac66fc6fef60  1b
>>>>>>> UN  10.136.11.40    4.24 MB    256     8.5%
>>>>>>> 66be1173-b822-40b5-b650-cb38ae3c7a51  1a
>>>>>>> UN  10.87.90.42     11.56 MB   256     8.0%
>>>>>>> dac0c6ea-56c6-44da-a4ec-6388f39ecba1  1b
>>>>>>> UN  10.87.75.147    549 MB     256     8.3%
>>>>>>> ac060edf-dc48-44cf-a1b5-83c7a465f3c8  1b
>>>>>>> UN  10.151.49.88    119.86 MB  256     8.9%
>>>>>>> 57043573-ab1b-4e3c-8044-58376f7ce08f  1a
>>>>>>> UN  10.87.83.107    484.3 MB   256     8.3%
>>>>>>> 0019439b-9f8a-4965-91b8-7108bbb55593  1b
>>>>>>> UN  10.137.20.183   137.67 MB  256     8.4%
>>>>>>> 15951592-8ab2-473d-920a-da6e9d99507d  1a
>>>>>>> UN  10.238.170.159  49.17 MB   256     9.4%
>>>>>>> 32ce322e-4f7c-46c7-a8ce-bd73cdd54684  1a
>>>>>>>
>>>>>>> Is there something else that I should be doing differently?
>>>>>>>
>>>>>>> Thanks for your help!
>>>>>>>
>>>>>>> Suruchi
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Thu, Sep 19, 2013 at 3:20 PM, Richard Low <richard@wentnet.com>wrote:
>>>>>>>
>>>>>>>> The only thing you need to guarantee is that Cassandra doesn't
>>>>>>>> start with num_tokens=1 (the default in 1.2.x) or, if it
does, that you
>>>>>>>> wipe all the data before starting it with higher num_tokens.
>>>>>>>>
>>>>>>>>
>>>>>>>> On 19 September 2013 19:07, Robert Coli <rcoli@eventbrite.com>wrote:
>>>>>>>>
>>>>>>>>> On Thu, Sep 19, 2013 at 10:59 AM, Suruchi Deodhar <
>>>>>>>>> suruchi.deodhar@generalsentiment.com> wrote:
>>>>>>>>>
>>>>>>>>>> Do you suggest I should try with some other installation
>>>>>>>>>> mechanism? Are there any known problems with the
tar installation of
>>>>>>>>>> cassandra 1.2.9 that I should be aware of?
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I was asking in the context of this JIRA :
>>>>>>>>>
>>>>>>>>> https://issues.apache.org/jira/browse/CASSANDRA-2356
>>>>>>>>>
>>>>>>>>> Which does not seem to apply in your case!
>>>>>>>>>
>>>>>>>>> =Rob
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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