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Posted to user@cassandra.apache.org by ibrahim El-sanosi <ib...@gmail.com> on 2015/08/21 17:48:24 UTC
Write request in Cassandra?
Dear folks,
I have doubt on how Cassandra performs a write request; I have two
scenarios, please read them and ensure which one is correct?
Assume we have cluster consists of 4 nodes N1, N2, N3, and N4. As Cassandra
distributes the nodes in ring topology, the nodes links as following:
N-->N-->N3-->N4-->N1
Also we have replication factor equal to 3 (RF=3), and consistency level
equals to ALL (CL=ALL).
Client sends write request, W, to coordinator, say N4. The partitioner has
determined the primary node of W is N1.
What will happen now?
*Scenario 1**:* coordinator sends W to N1. Upon receiving W, N1 stores it
locally (in commitLog and memtable, *please forget about internal process*)
and acknowledges the coordinator N4. Then N1 sends a copy of W to N2
(because N2 is next node in ring from N1 prospective). Upon receiving W, N2
stores it locally and sends acknowledgement to N4. Then N2 sends a copy of
W to N3 (because N3 is next node in ring from N2 prospective). Upon
receiving W, N3 stores it locally and acknowledges the Coordinator N4.
Finally as soon as coordinator, N4, receives an acknowledgement from all
nodes (N1, N2, and N3), it replays to the client.
Note that: if scenario 1 correct, then the latency will be 4 rounds (N4-->N1
-->N2-->N3-->N4 ----client).
*Scenario 2:* coordinator, N4, broadcasts W to N1, N2, and N3 (N4-->N1, N4
-->N2, N4-->N3). Then replicas (N1, N2, and N3) store W locally and
acknowledge to N4. When N4 receives all ACKs, it replays to client.
Can anyone confirm which scenario is correct in Cassandra?
Regards?
Ibrahim
Re: Write request in Cassandra?
Posted by Panagiotis Garefalakis <pa...@gmail.com>.
Definitely 2:
https://wiki.apache.org/cassandra/ArchitectureInternals
http://www.slideshare.net/grro/cassandra-by-example-the-path-of-read-and-write-requests
On Fri, Aug 21, 2015 at 4:54 PM, Laing, Michael <mi...@nytimes.com>
wrote:
>
> https://academy.datastax.com/courses/ds201-cassandra-core-concepts/internal-architecture-replication
>
> On Fri, Aug 21, 2015 at 11:53 AM, Laing, Michael <
> michael.laing@nytimes.com> wrote:
>
>> 2 is more correct.
>>
>> On Fri, Aug 21, 2015 at 11:48 AM, ibrahim El-sanosi <
>> ibrahimsabattt@gmail.com> wrote:
>>
>>> Dear folks,
>>>
>>>
>>> I have doubt on how Cassandra performs a write request; I have two
>>> scenarios, please read them and ensure which one is correct?
>>>
>>>
>>> Assume we have cluster consists of 4 nodes N1, N2, N3, and N4. As
>>> Cassandra distributes the nodes in ring topology, the nodes links as
>>> following:
>>>
>>> N-->N-->N3-->N4-->N1
>>>
>>> Also we have replication factor equal to 3 (RF=3), and consistency level
>>> equals to ALL (CL=ALL).
>>>
>>> Client sends write request, W, to coordinator, say N4. The partitioner
>>> has determined the primary node of W is N1.
>>>
>>> What will happen now?
>>>
>>>
>>> *Scenario 1**:* coordinator sends W to N1. Upon receiving W, N1 stores
>>> it locally (in commitLog and memtable, *please forget about internal
>>> process*) and acknowledges the coordinator N4. Then N1 sends a copy of
>>> W to N2 (because N2 is next node in ring from N1 prospective). Upon
>>> receiving W, N2 stores it locally and sends acknowledgement to N4. Then N2
>>> sends a copy of W to N3 (because N3 is next node in ring from N2
>>> prospective). Upon receiving W, N3 stores it locally and acknowledges the
>>> Coordinator N4. Finally as soon as coordinator, N4, receives an
>>> acknowledgement from all nodes (N1, N2, and N3), it replays to the client.
>>>
>>> Note that: if scenario 1 correct, then the latency will be 4 rounds (N4
>>> -->N1-->N2-->N3-->N4 ----client).
>>>
>>>
>>>
>>> *Scenario 2:* coordinator, N4, broadcasts W to N1, N2, and N3 (N4-->N1,
>>> N4-->N2, N4-->N3). Then replicas (N1, N2, and N3) store W locally and
>>> acknowledge to N4. When N4 receives all ACKs, it replays to client.
>>>
>>>
>>>
>>> Can anyone confirm which scenario is correct in Cassandra?
>>>
>>>
>>>
>>> Regards?
>>>
>>>
>>>
>>> Ibrahim
>>>
>>
>>
>
Re: Write request in Cassandra?
Posted by "Laing, Michael" <mi...@nytimes.com>.
https://academy.datastax.com/courses/ds201-cassandra-core-concepts/internal-architecture-replication
On Fri, Aug 21, 2015 at 11:53 AM, Laing, Michael <mi...@nytimes.com>
wrote:
> 2 is more correct.
>
> On Fri, Aug 21, 2015 at 11:48 AM, ibrahim El-sanosi <
> ibrahimsabattt@gmail.com> wrote:
>
>> Dear folks,
>>
>>
>> I have doubt on how Cassandra performs a write request; I have two
>> scenarios, please read them and ensure which one is correct?
>>
>>
>> Assume we have cluster consists of 4 nodes N1, N2, N3, and N4. As
>> Cassandra distributes the nodes in ring topology, the nodes links as
>> following:
>>
>> N-->N-->N3-->N4-->N1
>>
>> Also we have replication factor equal to 3 (RF=3), and consistency level
>> equals to ALL (CL=ALL).
>>
>> Client sends write request, W, to coordinator, say N4. The partitioner
>> has determined the primary node of W is N1.
>>
>> What will happen now?
>>
>>
>> *Scenario 1**:* coordinator sends W to N1. Upon receiving W, N1 stores
>> it locally (in commitLog and memtable, *please forget about internal
>> process*) and acknowledges the coordinator N4. Then N1 sends a copy of W
>> to N2 (because N2 is next node in ring from N1 prospective). Upon receiving
>> W, N2 stores it locally and sends acknowledgement to N4. Then N2 sends a
>> copy of W to N3 (because N3 is next node in ring from N2 prospective). Upon
>> receiving W, N3 stores it locally and acknowledges the Coordinator N4.
>> Finally as soon as coordinator, N4, receives an acknowledgement from all
>> nodes (N1, N2, and N3), it replays to the client.
>>
>> Note that: if scenario 1 correct, then the latency will be 4 rounds (N4
>> -->N1-->N2-->N3-->N4 ----client).
>>
>>
>>
>> *Scenario 2:* coordinator, N4, broadcasts W to N1, N2, and N3 (N4-->N1,
>> N4-->N2, N4-->N3). Then replicas (N1, N2, and N3) store W locally and
>> acknowledge to N4. When N4 receives all ACKs, it replays to client.
>>
>>
>>
>> Can anyone confirm which scenario is correct in Cassandra?
>>
>>
>>
>> Regards?
>>
>>
>>
>> Ibrahim
>>
>
>
Re: Write request in Cassandra?
Posted by "Laing, Michael" <mi...@nytimes.com>.
2 is more correct.
On Fri, Aug 21, 2015 at 11:48 AM, ibrahim El-sanosi <
ibrahimsabattt@gmail.com> wrote:
> Dear folks,
>
>
> I have doubt on how Cassandra performs a write request; I have two
> scenarios, please read them and ensure which one is correct?
>
>
> Assume we have cluster consists of 4 nodes N1, N2, N3, and N4. As
> Cassandra distributes the nodes in ring topology, the nodes links as
> following:
>
> N-->N-->N3-->N4-->N1
>
> Also we have replication factor equal to 3 (RF=3), and consistency level
> equals to ALL (CL=ALL).
>
> Client sends write request, W, to coordinator, say N4. The partitioner has
> determined the primary node of W is N1.
>
> What will happen now?
>
>
> *Scenario 1**:* coordinator sends W to N1. Upon receiving W, N1 stores it
> locally (in commitLog and memtable, *please forget about internal process*)
> and acknowledges the coordinator N4. Then N1 sends a copy of W to N2
> (because N2 is next node in ring from N1 prospective). Upon receiving W, N2
> stores it locally and sends acknowledgement to N4. Then N2 sends a copy of
> W to N3 (because N3 is next node in ring from N2 prospective). Upon
> receiving W, N3 stores it locally and acknowledges the Coordinator N4.
> Finally as soon as coordinator, N4, receives an acknowledgement from all
> nodes (N1, N2, and N3), it replays to the client.
>
> Note that: if scenario 1 correct, then the latency will be 4 rounds (N4-->
> N1-->N2-->N3-->N4 ----client).
>
>
>
> *Scenario 2:* coordinator, N4, broadcasts W to N1, N2, and N3 (N4-->N1,
> N4-->N2, N4-->N3). Then replicas (N1, N2, and N3) store W locally and
> acknowledge to N4. When N4 receives all ACKs, it replays to client.
>
>
>
> Can anyone confirm which scenario is correct in Cassandra?
>
>
>
> Regards?
>
>
>
> Ibrahim
>