ok, also make sure you use the latest patch version. 2.5.0 is old. 2.5.8
should be available today or in a few days.

On Wed, Dec 6, 2017 at 6:06 AM, Muthukumaran Kothandaraman <
muthu.kmk2...@gmail.com> wrote:

> Thanks Patrik.
>
> In fact, I use Cluster JMX + Jolokia to see how the status and unreachable
> node list changes and its perfectly in alignment with documented behavior.
> In fact, I am planning to use the JMX client to monitor formation of
> minority partitions to raise alarms as at now. Later we may consider using
> the partition info to take actions like isolation of nodes
>
> We are using Opendaylight RAFT consensus cluster built atop Akka.
>
> Regards
> Muthu
>
>
> On Tuesday, 5 December 2017 22:35:05 UTC+5:30, Patrik Nordwall wrote:
>>
>>
>>
>> On Mon, Dec 4, 2017 at 5:32 PM, Muthukumaran Kothandaraman <
>> muthu....@gmail.com> wrote:
>>
>>> Further observations
>>>
>>> I started suspecting that in the double fault scenario as below,
>>> auto-down-unreachable-after can play a significant role. As suspected,
>>> for TEST SCENARIO 3 below, when auto-down-unreachable-after was enabled
>>> with 10s delay when nodes moved from unreachable 'condition' (I
>>> understand that unreachable mainly a flag in cluster-status and not a state
>>> by itself) to Removed State ,TEST SCENARIO 3 below was able to allow the
>>> 3rd node join after all nodes 'saw' 3rd node as Down.
>>>
>>
>> I think you see in the logs for scenario 3 that the 3rd node is able to
>> join (log in 2nd node) and that it receives the Welcome message (log in 3rd
>> node). It is not moved to the Up state because there are still unreachable
>> nodes in the cluster, i.e. 1st node is still unreachable and not removed.
>> That is why you see that it works when you enable the auto-down.
>>
>> If you would also start 1st node and it joins again then it will also
>> work without auto-down, because when a node joins with same hostname and
>> port (different uid) that is enough evidence to safely remove the old
>> incarnation.
>>
>>
>>>
>>> I very well understand the consequence of enabling 
>>> auto-down-unreachable-after
>>> config parameter. That can lead to an array of issues (including but not
>>> limited to)
>>> false-positives in case of network partitions
>>>
>>> I request the clustering experts to comment if there are any
>>> alternatives other than enabling auto-down-unreachable-after.
>>>
>>
>> You'll probably find https://github.com/akka/akka-management useful when
>> you test those things. Then you can see current membership state and also
>> perform the downing of the 1st node manually. In the end you need some kind
>> of downing strategy, and as you know Lightbend has one as commercial
>> offering.
>>
>> Regards,
>> Patrik
>>
>>
>>>
>>> Thanks in advance
>>>
>>> Regards
>>> Muthu
>>>
>>>
>>>
>>>
>>>
>>> On Monday, 4 December 2017 14:34:15 UTC+5:30, Muthukumaran Kothandaraman
>>> wrote:
>>>>
>>>> Hi,
>>>>
>>>> I am trying to validate below statements in Akka Docs with slight twist
>>>> in the scenario. After first seed node is brought down and before
>>>> restarting the first seed-node, I try to restart another surviving node of
>>>> cluster
>>>>
>>>> "*When a new node is started it sends a message to all seed nodes and
>>>> then sends join command to the one that answers first.*"
>>>>
>>>> In conjunction with
>>>>
>>>> "*Once more than two seed nodes have been started it is no problem to
>>>> shut down the first seed node. If the first seed node is restarted, it will
>>>> first try to join the other seed nodes in the existing cluster.* "
>>>>
>>>> My configuration for 3 nodes (ie. 3 JVMs running on same machine) is as
>>>> following in same order :
>>>>
>>>>  cluster {
>>>>
>>>>    // URL format is 'akka://' for artery. When netty is to be enabled,
>>>>    // change this to 'akka.tcp://'
>>>>    seed-nodes = [
>>>>      "akka.tcp://ClusterSystem@127.0.0.1:25510",   // 1st Seed Node
>>>>      "akka.tcp://ClusterSystem@127.0.0.1:25520",   // 2nd Seed Node
>>>>      "akka.tcp://ClusterSystem@127.0.0.1:25530"    // 3rd Seed Node
>>>>    ]
>>>>
>>>>    seed-node-timeout = 12s
>>>>
>>>>    #auto-down-unreachable-after = 10s
>>>>
>>>>    #allow-weakly-up-members = on
>>>>  }
>>>>
>>>>
>>>>
>>>> *TEST SCENARIO 1 (PASSED)* : Bring up nodes in any order and form the 
>>>> cluster
>>>>
>>>>
>>>> *TEST SCENARIO 2 (PASSED)* : After cluster is formed, bring down the first 
>>>> seed node (ie. akka.tcp://ClusterSystem@127.0.0.1:25510).
>>>>
>>>>                   Ensure remaining cluster works without any disruption
>>>>
>>>>
>>>> *TEST SCENARIO 3 (NOT PASSING**)* : Bring down 3rd node 
>>>> (akka.tcp://ClusterSystem@127.0.0.1:25530) when 1st seed node is still 
>>>> DOWN. And then bring up 3rd node.
>>>>
>>>>                                     As I understand from first referred 
>>>> statement from documentation, 3rd seed node must be able to join 2nd 
>>>> seed-node even when 1st node is down
>>>>
>>>>                                     But the observation is that 3rd seed 
>>>> node does NOT join the cluster.
>>>>
>>>>
>>>> Of course, only when 2nd node is surviving and I bring up 1st as well as 
>>>> 3rd node, cluster forms correctly again
>>>>
>>>>
>>>>
>>>> *Clarification :*
>>>>
>>>>
>>>> 1) Documentation mentions "once more than 2 seed nodes have been started". 
>>>> Does that mean that my TEST SCENARIO 3 above is invalid ? In other words, 
>>>> at any point in time,
>>>>
>>>>   I should have at least 2 seed nodes of cluster to be alive make the TEST 
>>>> SCENARIO 3 above pass ?
>>>>
>>>>
>>>> 2) And, if there are double faults like TEST SCENARIO 3, will cluster not 
>>>> converge till we perform full cluster reboot or bring back the first node 
>>>> in seed node list ?
>>>>
>>>>
>>>>
>>>> Regards
>>>>
>>>> Muthu
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> --
>>> >>>>>>>>>> Read the docs: http://akka.io/docs/
>>> >>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/c
>>> urrent/additional/faq.html
>>> >>>>>>>>>> Search the archives: https://groups.google.com/grou
>>> p/akka-user
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>>
>>
>>
>> --
>>
>> Patrik Nordwall
>> Akka Tech Lead
>> Lightbend <http://www.lightbend.com/> -  Reactive apps on the JVM
>> Twitter: @patriknw
>>
>> --
> >>>>>>>>>> Read the docs: http://akka.io/docs/
> >>>>>>>>>> Check the FAQ: http://doc.akka.io/docs/akka/
> current/additional/faq.html
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-- 

Patrik Nordwall
Akka Tech Lead
Lightbend <http://www.lightbend.com/> -  Reactive apps on the JVM
Twitter: @patriknw

-- 
>>>>>>>>>>      Read the docs: http://akka.io/docs/
>>>>>>>>>>      Check the FAQ: 
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>>      Search the archives: https://groups.google.com/group/akka-user
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