Re: Split brain problem in 2 node elasticsearch cluster

2015-05-05 Thread Ivan Brusic 
In non "big data" scenarios, having two servers for a database is simply
done to achieve high availability. Most databases use a master client
scenario, but Elasticsearch does not support such a setup. It really should
because not everyone has tons of data.

Ivan, not affiliated with the OP
On May 4, 2015 8:32 AM, "Jason Wee"  wrote:

> why must you have only two nodes, would it be possible to add one more
> nodes so split brain will not become an issue?
>
> jason
>
> On Mon, May 4, 2015 at 2:20 PM, Mark Walkom  wrote:
>
>> Your nodes aren't in different DCs are they? If so this is why we don't
>> support such setups, because ES is latency sensitive and these sorts of
>> things can happen very easily when your network is unreliable.
>>
>> They don't try to ping other nodes because you only have two, and if they
>> lose contact with one another then they both assume they are masters and
>> create their own cluster. Masters don't ping other nodes at random and see
>> if they should be joining a different cluster.
>>
>> Logically there is no difference between a primary and a replica shard,
>> the only physical difference is a flag that tells the cluster state which
>> is which. This is why ES will never assign a primary and it's applicable
>> replica to the same node.
>>
>>
>> You cannot get around the root of your problem unless you add another
>> node to and set min masters to ensure a majority quorum.
>>
>> On 4 May 2015 at 15:27, Gourav H Dhelaria 
>> wrote:
>>
>>>
>>> 1) After network goes down, they loose communication with each other.
>>> After that, they are becoming split.
>>> 2) They both think they are masters. Even if they think they are
>>> masters, shouldn't the ping happen to see if there are other nodes in the
>>> cluster ?
>>> 3) Number of replicas is set to 1. If ES doesn't differentiate, why are
>>> some shards primary and others replica ?
>>>
>>>
>>> On Monday, 4 May 2015 10:48:24 UTC+5:30, Mark Walkom wrote:


1. Why are they becoming split anyway? GC, other load, network?
2. Not if they both think they are masters.
3. Are you running replicas? If so ES doesn't really differentiate
between the two.


 On 4 May 2015 at 15:03, Gourav H Dhelaria  wrote:

> Version: 1.4.
> Say there are 2 nodes X and Y, both capable of becoming master.
> When network goes down, both nodes get disconnected from each other
> and assume the responsibility of master.
> When network is restored, they don't ping each other and form a
> cluster.
>
> Elasticsearch service has to be restarted on any one of the nodes for
> them to form a cluster. Even after they form a cluster, all primary shards
> remain on one node ( on which the service was restarted ), and all replica
> shards are on the other node.
>
>
> This document
>
>
> http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html
>
>
> mentions that there has to be an uneven number of master eligible
> nodes.
>
>
> Queries:
>
>
> 1) Is there a way of avoiding split brain problem in 2 node cluster ?
>
> 2) After network is restored, shouldn't the nodes ping each other and
> form a cluster ?
>
> 3) After the service is restarted to form the cluster, why don't the
> primary shards get distributed on both the nodes ?
>
>
>
> Thanks,
>
> Gourav
>
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> 
> .
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Re: Split brain problem in 2 node elasticsearch cluster

2015-05-05 Thread Gourav H Dhelaria 
Looks like the only way around this would be to add more nodes and set 
minimum masters to ensure a majority quorum.

Thanks.



Gourav

On Monday, 4 May 2015 12:02:27 UTC+5:30, Jason Wee wrote:
>
> why must you have only two nodes, would it be possible to add one more 
> nodes so split brain will not become an issue?
>
> jason
>
> On Mon, May 4, 2015 at 2:20 PM, Mark Walkom  > wrote:
>
>> Your nodes aren't in different DCs are they? If so this is why we don't 
>> support such setups, because ES is latency sensitive and these sorts of 
>> things can happen very easily when your network is unreliable.
>>
>> They don't try to ping other nodes because you only have two, and if they 
>> lose contact with one another then they both assume they are masters and 
>> create their own cluster. Masters don't ping other nodes at random and see 
>> if they should be joining a different cluster.
>>
>> Logically there is no difference between a primary and a replica shard, 
>> the only physical difference is a flag that tells the cluster state which 
>> is which. This is why ES will never assign a primary and it's applicable 
>> replica to the same node.
>>
>>
>> You cannot get around the root of your problem unless you add another 
>> node to and set min masters to ensure a majority quorum.
>>
>> On 4 May 2015 at 15:27, Gourav H Dhelaria > > wrote:
>>
>>>
>>> 1) After network goes down, they loose communication with each other. 
>>> After that, they are becoming split.
>>> 2) They both think they are masters. Even if they think they are 
>>> masters, shouldn't the ping happen to see if there are other nodes in the 
>>> cluster ?
>>> 3) Number of replicas is set to 1. If ES doesn't differentiate, why are 
>>> some shards primary and others replica ?
>>>
>>>
>>> On Monday, 4 May 2015 10:48:24 UTC+5:30, Mark Walkom wrote:


1. Why are they becoming split anyway? GC, other load, network?
2. Not if they both think they are masters.
3. Are you running replicas? If so ES doesn't really differentiate 
between the two.


 On 4 May 2015 at 15:03, Gourav H Dhelaria  wrote:

> Version: 1.4. 
> Say there are 2 nodes X and Y, both capable of becoming master. 
> When network goes down, both nodes get disconnected from each other 
> and assume the responsibility of master. 
> When network is restored, they don't ping each other and form a 
> cluster.
>
> Elasticsearch service has to be restarted on any one of the nodes for 
> them to form a cluster. Even after they form a cluster, all primary 
> shards 
> remain on one node ( on which the service was restarted ), and all 
> replica 
> shards are on the other node.
>
>
> This document
>
>
> http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html
>
>
> mentions that there has to be an uneven number of master eligible 
> nodes.
>
>
> Queries:
>
>
> 1) Is there a way of avoiding split brain problem in 2 node cluster ?
>
> 2) After network is restored, shouldn't the nodes ping each other and 
> form a cluster ?
>
> 3) After the service is restarted to form the cluster, why don't the 
> primary shards get distributed on both the nodes ?
>
>
>
> Thanks,
>
> Gourav
>
> -- 
> You received this message because you are subscribed to the Google 
> Groups "elasticsearch" group.
> To unsubscribe from this group and stop receiving emails from it, send 
> an email to elasticsearc...@googlegroups.com.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/elasticsearch/d15234b3-0ea1-4390-b136-2f02f69cd3f5%40googlegroups.com
>  
> 
> .
> For more options, visit https://groups.google.com/d/optout.
>

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Re: Split brain problem in 2 node elasticsearch cluster

2015-05-03 Thread Jason Wee 
why must you have only two nodes, would it be possible to add one more
nodes so split brain will not become an issue?

jason

On Mon, May 4, 2015 at 2:20 PM, Mark Walkom  wrote:

> Your nodes aren't in different DCs are they? If so this is why we don't
> support such setups, because ES is latency sensitive and these sorts of
> things can happen very easily when your network is unreliable.
>
> They don't try to ping other nodes because you only have two, and if they
> lose contact with one another then they both assume they are masters and
> create their own cluster. Masters don't ping other nodes at random and see
> if they should be joining a different cluster.
>
> Logically there is no difference between a primary and a replica shard,
> the only physical difference is a flag that tells the cluster state which
> is which. This is why ES will never assign a primary and it's applicable
> replica to the same node.
>
>
> You cannot get around the root of your problem unless you add another node
> to and set min masters to ensure a majority quorum.
>
> On 4 May 2015 at 15:27, Gourav H Dhelaria 
> wrote:
>
>>
>> 1) After network goes down, they loose communication with each other.
>> After that, they are becoming split.
>> 2) They both think they are masters. Even if they think they are masters,
>> shouldn't the ping happen to see if there are other nodes in the cluster ?
>> 3) Number of replicas is set to 1. If ES doesn't differentiate, why are
>> some shards primary and others replica ?
>>
>>
>> On Monday, 4 May 2015 10:48:24 UTC+5:30, Mark Walkom wrote:
>>>
>>>
>>>1. Why are they becoming split anyway? GC, other load, network?
>>>2. Not if they both think they are masters.
>>>3. Are you running replicas? If so ES doesn't really differentiate
>>>between the two.
>>>
>>>
>>> On 4 May 2015 at 15:03, Gourav H Dhelaria  wrote:
>>>
 Version: 1.4.
 Say there are 2 nodes X and Y, both capable of becoming master.
 When network goes down, both nodes get disconnected from each other and
 assume the responsibility of master.
 When network is restored, they don't ping each other and form a cluster.

 Elasticsearch service has to be restarted on any one of the nodes for
 them to form a cluster. Even after they form a cluster, all primary shards
 remain on one node ( on which the service was restarted ), and all replica
 shards are on the other node.


 This document


 http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html


 mentions that there has to be an uneven number of master eligible nodes.


 Queries:


 1) Is there a way of avoiding split brain problem in 2 node cluster ?

 2) After network is restored, shouldn't the nodes ping each other and
 form a cluster ?

 3) After the service is restarted to form the cluster, why don't the
 primary shards get distributed on both the nodes ?



 Thanks,

 Gourav

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Re: Split brain problem in 2 node elasticsearch cluster

2015-05-03 Thread Mark Walkom 
Your nodes aren't in different DCs are they? If so this is why we don't
support such setups, because ES is latency sensitive and these sorts of
things can happen very easily when your network is unreliable.

They don't try to ping other nodes because you only have two, and if they
lose contact with one another then they both assume they are masters and
create their own cluster. Masters don't ping other nodes at random and see
if they should be joining a different cluster.

Logically there is no difference between a primary and a replica shard, the
only physical difference is a flag that tells the cluster state which is
which. This is why ES will never assign a primary and it's applicable
replica to the same node.


You cannot get around the root of your problem unless you add another node
to and set min masters to ensure a majority quorum.

On 4 May 2015 at 15:27, Gourav H Dhelaria  wrote:

>
> 1) After network goes down, they loose communication with each other.
> After that, they are becoming split.
> 2) They both think they are masters. Even if they think they are masters,
> shouldn't the ping happen to see if there are other nodes in the cluster ?
> 3) Number of replicas is set to 1. If ES doesn't differentiate, why are
> some shards primary and others replica ?
>
>
> On Monday, 4 May 2015 10:48:24 UTC+5:30, Mark Walkom wrote:
>>
>>
>>1. Why are they becoming split anyway? GC, other load, network?
>>2. Not if they both think they are masters.
>>3. Are you running replicas? If so ES doesn't really differentiate
>>between the two.
>>
>>
>> On 4 May 2015 at 15:03, Gourav H Dhelaria  wrote:
>>
>>> Version: 1.4.
>>> Say there are 2 nodes X and Y, both capable of becoming master.
>>> When network goes down, both nodes get disconnected from each other and
>>> assume the responsibility of master.
>>> When network is restored, they don't ping each other and form a cluster.
>>>
>>> Elasticsearch service has to be restarted on any one of the nodes for
>>> them to form a cluster. Even after they form a cluster, all primary shards
>>> remain on one node ( on which the service was restarted ), and all replica
>>> shards are on the other node.
>>>
>>>
>>> This document
>>>
>>>
>>> http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html
>>>
>>>
>>> mentions that there has to be an uneven number of master eligible nodes.
>>>
>>>
>>> Queries:
>>>
>>>
>>> 1) Is there a way of avoiding split brain problem in 2 node cluster ?
>>>
>>> 2) After network is restored, shouldn't the nodes ping each other and
>>> form a cluster ?
>>>
>>> 3) After the service is restarted to form the cluster, why don't the
>>> primary shards get distributed on both the nodes ?
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Gourav
>>>
>>> --
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>>> Groups "elasticsearch" group.
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>>> 
>>> .
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
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Re: Split brain problem in 2 node elasticsearch cluster

2015-05-03 Thread Gourav H Dhelaria 

1) After network goes down, they loose communication with each other. After 
that, they are becoming split.
2) They both think they are masters. Even if they think they are masters, 
shouldn't the ping happen to see if there are other nodes in the cluster ?
3) Number of replicas is set to 1. If ES doesn't differentiate, why are 
some shards primary and others replica ?


On Monday, 4 May 2015 10:48:24 UTC+5:30, Mark Walkom wrote:
>
>
>1. Why are they becoming split anyway? GC, other load, network?
>2. Not if they both think they are masters.
>3. Are you running replicas? If so ES doesn't really differentiate 
>between the two.
>
>
> On 4 May 2015 at 15:03, Gourav H Dhelaria  > wrote:
>
>> Version: 1.4. 
>> Say there are 2 nodes X and Y, both capable of becoming master. 
>> When network goes down, both nodes get disconnected from each other and 
>> assume the responsibility of master. 
>> When network is restored, they don't ping each other and form a cluster.
>>
>> Elasticsearch service has to be restarted on any one of the nodes for 
>> them to form a cluster. Even after they form a cluster, all primary shards 
>> remain on one node ( on which the service was restarted ), and all replica 
>> shards are on the other node.
>>
>>
>> This document
>>
>>
>> http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html
>>
>>
>> mentions that there has to be an uneven number of master eligible nodes.
>>
>>
>> Queries:
>>
>>
>> 1) Is there a way of avoiding split brain problem in 2 node cluster ?
>>
>> 2) After network is restored, shouldn't the nodes ping each other and 
>> form a cluster ?
>>
>> 3) After the service is restarted to form the cluster, why don't the 
>> primary shards get distributed on both the nodes ?
>>
>>
>>
>> Thanks,
>>
>> Gourav
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "elasticsearch" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to elasticsearc...@googlegroups.com .
>> To view this discussion on the web visit 
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>>  
>> 
>> .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

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Re: Split brain problem in 2 node elasticsearch cluster

2015-05-03 Thread Mark Walkom 
   1. Why are they becoming split anyway? GC, other load, network?
   2. Not if they both think they are masters.
   3. Are you running replicas? If so ES doesn't really differentiate
   between the two.


On 4 May 2015 at 15:03, Gourav H Dhelaria  wrote:

> Version: 1.4.
> Say there are 2 nodes X and Y, both capable of becoming master.
> When network goes down, both nodes get disconnected from each other and
> assume the responsibility of master.
> When network is restored, they don't ping each other and form a cluster.
>
> Elasticsearch service has to be restarted on any one of the nodes for them
> to form a cluster. Even after they form a cluster, all primary shards
> remain on one node ( on which the service was restarted ), and all replica
> shards are on the other node.
>
>
> This document
>
>
> http://www.elastic.co/guide/en/elasticsearch/guide/current/_important_configuration_changes.html
>
>
> mentions that there has to be an uneven number of master eligible nodes.
>
>
> Queries:
>
>
> 1) Is there a way of avoiding split brain problem in 2 node cluster ?
>
> 2) After network is restored, shouldn't the nodes ping each other and form
> a cluster ?
>
> 3) After the service is restarted to form the cluster, why don't the
> primary shards get distributed on both the nodes ?
>
>
>
> Thanks,
>
> Gourav
>
> --
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> .
> For more options, visit https://groups.google.com/d/optout.
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