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From Matthew Allen <matthew.j.al...@gmail.com>
Subject Re: Multi-DC Repairs and Token Questions
Date Tue, 03 Jun 2014 01:57:09 GMT
Hi Rameez, Chovatia, (sorry I initially replied to Dwight individually)

SN_KEYSPACE and MY_KEYSPACE are just typos (was try to mask out
identifiable information), they are same keyspace.

Keyspace: SN_KEYSPACE:
  Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy
  Durable Writes: true
    Options: [DC_VIC:2, DC_NSW:2]

In a nutshell, replication is working as expected, I'm just confused about
token range assignments in a Multi-DC environment and how repairs should
work

From
http://www.datastax.com/documentation/cassandra/1.2/cassandra/configuration/configGenTokens_c.html,
it specifies

*        "Multiple data center deployments: calculate the tokens for each
data center so that the hash range is evenly divided for the nodes in each
data center"*

Given that nodetool -repair isn't multi-dc aware, in our production 18 node
cluster (9 nodes in each DC), which of the following token ranges should be
used (Murmur3 Partitioner) ?

Token range divided evenly over the 2 DC's/18 nodes as below ?

Node DC_NSW                    DC_VIC
1    '-9223372036854775808'    '-8198552921648689608'
2    '-7173733806442603408'    '-6148914691236517208'
3    '-5124095576030431008'    '-4099276460824344808'
4    '-3074457345618258608'    '-2049638230412172408'
5    '-1024819115206086208'    '-8'
6    '1024819115206086192'     '2049638230412172392'
7    '3074457345618258592'     '4099276460824344792'
8    '5124095576030430992'     '6148914691236517192'
9    '7173733806442603392'     '8198552921648689592'

Or An offset used for DC_VIC (i.e. DC_NSW + 100) ?

Node     DC_NSW                 DC_VIC
1     '-9223372036854775808'    '-9223372036854775708'
2     '-7173733806442603407'    '-7173733806442603307'
3     '-5124095576030431006'    '-5124095576030430906'
4     '-3074457345618258605'    '-3074457345618258505'
5     '-1024819115206086204'    '-1024819115206086104'
6     '1024819115206086197'     '1024819115206086297'
7     '3074457345618258598'     '3074457345618258698'
8     '5124095576030430999'     '5124095576030431099'
9     '7173733806442603400'     '7173733806442603500'

It's too late for me to switch to vnodes, hope that makes sense, thanks

Matt



On Thu, May 29, 2014 at 12:01 AM, Rameez Thonnakkal <ssrameez@gmail.com>
wrote:

> as Chovatia mentioned, the keyspaces seems to be different.
> try "Describe keyspace SN_KEYSPACE" and "describe keyspace MY_KEYSPACE"
> from CQL.
> This will give you an idea about how many replicas are there for these
> keyspaces.
>
>
>
> On Wed, May 28, 2014 at 11:49 AM, chovatia jaydeep <
> chovatia_jaydeep@yahoo.co.in> wrote:
>
>> What is your partition type? Is
>> it org.apache.cassandra.dht.Murmur3Partitioner?
>> In your repair command i do see there are two different KeySpaces "MY_KEYSPACE"
>> and "SN_KEYSPACE", are these two separate key spaces or typo?
>>
>> -jaydeep
>>
>>
>>   On Tuesday, 27 May 2014 10:26 PM, Matthew Allen <
>> matthew.j.allen@gmail.com> wrote:
>>
>>
>> Hi,
>>
>> Am a bit confused regarding data ownership in a multi-dc environment.
>>
>> I have the following setup in a test cluster with a keyspace with
>> (placement_strategy = 'NetworkTopologyStrategy' and strategy_options =
>> {'DC_NSW':2,'DC_VIC':2};)
>>
>> Datacenter: DC_NSW
>> ==========
>> Replicas: 2
>> Address         Rack        Status State   Load
>> Owns                Token
>>
>> 0
>> nsw1  rack1       Up     Normal  1007.43 MB      100.00%
>> -9223372036854775808
>> nsw2  rack1       Up     Normal  1008.08 MB      100.00%             0
>>
>>
>> Datacenter: DC_VIC
>> ==========
>> Replicas: 2
>> Address         Rack        Status State   Load
>> Owns                Token
>>
>> 100
>> vic1   rack1       Up     Normal  1015.1 MB       100.00%
>> -9223372036854775708
>> vic2   rack1       Up     Normal  1015.13 MB      100.00%             100
>>
>> My understanding is that both Datacenters have a complete copy of the
>> data, but when I run a repair -pr on each of the nodes, the vic hosts only
>> take a couple of seconds, while the nsw nodes take about 5 minutes each.
>>
>> Does this mean that nsw nodes "own" the majority of the data given their
>> key ranges and that repairs will need to cross datacenters ?
>>
>> Thanks
>>
>> Matt
>>
>> command>nodetool -h vic1 repair -pr   (takes seconds)
>> Starting NodeTool
>> [2014-05-28 15:11:02,783] Starting repair command #1, repairing 1 ranges
>> for keyspace MY_KEYSPACE
>> [2014-05-28 15:11:03,110] Repair session
>> 76d170f0-e626-11e3-af4e-218541ad23a1 for range
>> (-9223372036854775808,-9223372036854775708] finished
>> [2014-05-28 15:11:03,110] Repair command #1 finished
>> [2014-05-28 15:11:03,126] Nothing to repair for keyspace 'system'
>> [2014-05-28 15:11:03,126] Nothing to repair for keyspace 'system_traces'
>>
>> command>nodetool -h vic2 repair -pr (takes seconds)
>> Starting NodeTool
>> [2014-05-28 15:11:28,746] Starting repair command #1, repairing 1 ranges
>> for keyspace MY_KEYSPACE
>> [2014-05-28 15:11:28,840] Repair session
>> 864b14a0-e626-11e3-9612-07b0c029e3c7 for range (0,100] finished
>> [2014-05-28 15:11:28,840] Repair command #1 finished
>> [2014-05-28 15:11:28,866] Nothing to repair for keyspace 'system'
>> [2014-05-28 15:11:28,866] Nothing to repair for keyspace 'system_traces'
>>
>> command>nodetool -h nsw1 repair -pr (takes minutes)
>> Starting NodeTool
>> [2014-05-28 15:11:32,579] Starting repair command #1, repairing 1 ranges
>> for keyspace SN_KEYSPACE
>> [2014-05-28 15:14:07,187] Repair session
>> 88966430-e626-11e3-81eb-c991646ac2bf for range (100,-9223372036854775808]
>> finished
>> [2014-05-28 15:14:07,187] Repair command #1 finished
>> [2014-05-28 15:14:11,393] Nothing to repair for keyspace 'system'
>> [2014-05-28 15:14:11,440] Nothing to repair for keyspace 'system_traces'
>>
>> command>nodetool -h nsw2 repair -pr (takes minutes)
>> Starting NodeTool
>> [2014-05-28 15:14:18,670] Starting repair command #1, repairing 1 ranges
>> for keyspace SN_KEYSPACE
>> [2014-05-28 15:17:27,300] Repair session
>> eb936ce0-e626-11e3-81e2-8790242f886e for range (-9223372036854775708,0]
>> finished
>> [2014-05-28 15:17:27,300] Repair command #1 finished
>> [2014-05-28 15:17:32,017] Nothing to repair for keyspace 'system'
>> [2014-05-28 15:17:32,064] Nothing to repair for keyspace 'system_traces'
>>
>>
>>
>

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