Also, please don't do that:
cluster.leave(cluster.selfAddress());
system.terminate();
It is wrong.
You need to give the cluster gossip enough time to complete the leaving
"nicely".
Proper graceful shutdown means you need to wait for _your own_ address to
come back as MemberRemoved event,
and THEN you can shut down the actor system and JVM.
Related:
this mistake is exactly something I warn against in my recent talk "Zen of
Akka", you may enjoy it :-)
https://youtu.be/tC-joPMPJLs
On Fri, Mar 18, 2016 at 5:58 PM, Patrik Nordwall <patrik.nordw...@gmail.com>
wrote:
> Hi Ben
>
> There are some subtle exceptions to the convergence rule. Unreachable
> members with status Down or Exiting are not counted.
>
> /Patrik
>
> On Thu, Mar 17, 2016 at 11:25 PM, Guido Medina <oxyg...@gmail.com> wrote:
>
>> In fact in the other nodes you get the following:
>>
>> INFO 22:10:20,383 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Leader is moving node [akka.tcp://
>> DevCluster@127.0.0.1:38845] to [Exiting]
>> INFO 22:10:20,384 orRef - Message [akka.cluster.GossipEnvelope] from
>> Actor[akka://DevCluster/system/cluster/core/daemon#1435915897] to
>> Actor[akka://DevCluster/deadLetters] was not delivered. [1] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:20,403 orRef - Message [akka.cluster.
>> ClusterHeartbeatSender$Heartbeat] from
>> Actor[akka://DevCluster/system/cluster/core/daemon/heartbeatSender#1423910769]
>> to Actor[akka://DevCluster/deadLetters] was not delivered. [2] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:21,383 orRef - Message [akka.cluster.GossipEnvelope] from
>> Actor[akka://DevCluster/system/cluster/core/daemon#1435915897] to
>> Actor[akka://DevCluster/deadLetters] was not delivered. [3] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:21,403 orRef - Message [akka.cluster.
>> ClusterHeartbeatSender$Heartbeat] from
>> Actor[akka://DevCluster/system/cluster/core/daemon/heartbeatSender#1423910769]
>> to Actor[akka://DevCluster/deadLetters] was not delivered. [4] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:22,383 orRef - Message [akka.cluster.GossipEnvelope] from
>> Actor[akka://DevCluster/system/cluster/core/daemon#1435915897] to
>> Actor[akka://DevCluster/deadLetters] was not delivered. [5] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:22,403 orRef - Message [akka.cluster.
>> ClusterHeartbeatSender$Heartbeat] from
>> Actor[akka://DevCluster/system/cluster/core/daemon/heartbeatSender#1423910769]
>> to Actor[akka://DevCluster/deadLetters] was not delivered. [6] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:23,383 orRef - Message [akka.cluster.GossipEnvelope] from
>> Actor[akka://DevCluster/system/cluster/core/daemon#1435915897] to
>> Actor[akka://DevCluster/deadLetters] was not delivered. [7] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:23,403 orRef - Message [akka.cluster.
>> ClusterHeartbeatSender$Heartbeat] from
>> Actor[akka://DevCluster/system/cluster/core/daemon/heartbeatSender#1423910769]
>> to Actor[akka://DevCluster/deadLetters] was not delivered. [8] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:24,382 orRef - Message [akka.cluster.GossipEnvelope] from
>> Actor[akka://DevCluster/system/cluster/core/daemon#1435915897] to
>> Actor[akka://DevCluster/deadLetters] was not delivered. [9] dead letters
>> encountered. This logging can be turned off or adjusted with configuration
>> settings 'akka.log-dead-letters' and
>> 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:24,384 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Marking exiting node(s) as UNREACHABLE
>> [Member(address = akka.tcp://DevCluster@127.0.0.1:38845, status =
>> Exiting)]. This is expected and they will be removed.
>> INFO 22:10:24,403 orRef - Message [akka.cluster.
>> ClusterHeartbeatSender$Heartbeat] from
>> Actor[akka://DevCluster/system/cluster/core/daemon/heartbeatSender#1423910769]
>> to Actor[akka://DevCluster/deadLetters] was not delivered. [10] dead
>> letters encountered, no more dead letters will be logged. This logging can
>> be turned off or adjusted with configuration settings
>> 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.
>> INFO 22:10:25,387 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Leader is removing exiting node [akka.tcp://
>> DevCluster@127.0.0.1:38845]
>>
>> Notice the 1st status is [Exiting], then you see from [Exiting] to
>> [Unreachable] and then you get [MemberRemoved] which isn't logged by Akka
>> but I can assure you it happens, and if you log the events the last two
>> will be:
>>
>> INFO 22:23:00,968 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Leader is auto-downing unreachable node
>> [akka.tcp://DevCluster@127.0.0.1:54621]
>> INFO 22:23:00,969 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Marking unreachable node [akka.tcp://
>> DevCluster@127.0.0.1:54621] as [Down]
>> INFO 22:23:01,952 ster) - Cluster Node [akka.tcp://
>> DevCluster@127.0.0.1:2552] - Leader is removing unreachable node
>> [akka.tcp://DevCluster@127.0.0.1:54621]
>> INFO 22:23:01,966 visor - MemberRemoved(Member(address = akka.tcp://
>> DevCluster@127.0.0.1:54621, status = Removed),Down)
>>
>> The last message is the one I rely upon, same as:
>>
>> INFO 22:22:39,954 visor - MemberUp(Member(address = akka.tcp://
>> DevCluster@127.0.0.1:54621, status = Up))
>>
>> Regards,
>>
>> Guido.
>>
>> On Thursday, March 17, 2016 at 10:15:52 PM UTC, Guido Medina wrote:
>>>
>>> I just tried this:
>>>
>>> final Cluster cluster = Cluster.get(system);
>>> cluster.leave(cluster.selfAddress());
>>> try {
>>> Thread.sleep(1000);
>>> } catch (InterruptedException ignored) {
>>> }
>>> system.terminate();
>>>
>>> and it didn't work, still the dead node has to timeout in the others,
>>> in other words I don't see any cluster event message coming to the node
>>> that just left so by default I'm just shutting down letting gossip failures
>>> take care of it,
>>> and reacting only upon MemberUp and MemberRemoved instead, I have that
>>> working for like 10 months now no problem.
>>>
>>> Regards,
>>>
>>> Guido.
>>>
>>> On Thursday, March 17, 2016 at 10:04:27 PM UTC, Benjamin Black wrote:
>>>>
>>>> Hi Guido,
>>>>
>>>> I think in your case you are shutting down before the node has
>>>> communicated to the leader that it wants to leave. I wait to get the
>>>> MemberExited message before shutting down the node. Maybe I should wait for
>>>> the MemberRemoved? Either way the ultimate aim is to not have the
>>>> unreachable logic kick in and have to wait x seconds (I use 10 seconds) for
>>>> the node to be auto downed by the leader. And the reason why I don't want
>>>> to wait is according to the docs the leader wouldn't be able to add nodes
>>>> whilst any node in the cluster is considered unreachable, which is a
>>>> problem if I'm doing a rolling restart of all the nodes.
>>>>
>>>> Regards,
>>>> Ben
>>>>
>>>> On Thursday, March 17, 2016 at 4:51:30 PM UTC-4, Guido Medina wrote:
>>>>>
>>>>> As for cluster.leave(cluster.selfAddress) my micro-services use the
>>>>> following to leave:
>>>>>
>>>>> Runtime.getRuntime().addShutdownHook(new Thread() {
>>>>> @Override
>>>>> public void run() {
>>>>> final Cluster cluster = Cluster.get(system);
>>>>> cluster.leave(cluster.selfAddress());
>>>>> system.terminate();
>>>>> Configurator.shutdown((LoggerContext) LogManager.getContext
>>>>> ());
>>>>> }
>>>>> });
>>>>>
>>>>> But honestly I have never seen that work, the other nodes just report
>>>>> it as unreachable until it times out and it is completely removed,
>>>>> maybe the shutdown happens so fast that it is useless in my case.
>>>>>
>>>>> HTH,
>>>>>
>>>>> Guido.
>>>>>
>>>>> On Thursday, March 17, 2016 at 8:33:29 PM UTC, Guido Medina wrote:
>>>>>>
>>>>>> Hi Benjamin,
>>>>>>
>>>>>> I also rely on cluster events and AFAIK you can expect (and trust)
>>>>>> *MemberUp* and *MemberRemoved*, these IMHO are the only two
>>>>>> consistent states you can trust.
>>>>>> In other words, I register some actors only when their nodes reach
>>>>>> *MemberUp* and unregister only when their nodes reach *MemberRemoved*
>>>>>> Any other state in between I would treat them as information only.
>>>>>>
>>>>>> So far I haven't got any issue with my mini-shard implementation
>>>>>> relying on these only 2 statuses, the draw back is that it will only have
>>>>>> to wait for a longer time to react.
>>>>>>
>>>>>> HTH,
>>>>>>
>>>>>> Guido.
>>>>>>
>>>>>> On Thursday, March 17, 2016 at 6:07:48 PM UTC, Benjamin Black wrote:
>>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> I'm adding logic to our service so that when a node is being
>>>>>>> restarted it gracefully leaves the cluster using cluster.leave(
>>>>>>> cluster.selfAddress). In the cluster specification doc it states:
>>>>>>>
>>>>>>> If a node is unreachable then gossip convergence is not possible
>>>>>>> and therefore any leader actions are also not possible (for
>>>>>>> instance, allowing a node to become a part of the cluster). To be able
>>>>>>> to
>>>>>>> move forward the state of theunreachable nodes must be changed. It
>>>>>>> must become reachable again or marked as down
>>>>>>>
>>>>>>> Is this totally true? If a node is unreachable and is the
>>>>>>> leaving/exiting/removed state will this stop the leader from adding a
>>>>>>> new
>>>>>>> node? I ask because I have an actor that subscribes to cluster events
>>>>>>> and I
>>>>>>> can see a node is being added whilst another node is considered
>>>>>>> unreachable
>>>>>>> and in the exiting status:
>>>>>>>
>>>>>>> 14:02:46.843 INFO Exited member Member(address = akka.tcp://
>>>>>>> geyser@172.16.120.160:7000, status = Exiting)
>>>>>>> 14:02:51.842 INFO Unreachable member Member(address = akka.tcp://
>>>>>>> geyser@172.16.120.160:7000, status = Exiting)
>>>>>>> 14:02:53.843 INFO Removing member Member(address = akka.tcp://
>>>>>>> geyser@172.16.120.160:7000, status = Removed)
>>>>>>> 14:02:57.843 INFO Exited member Member(address = akka.tcp://
>>>>>>> geyser@172.16.119.46:7000, status = Exiting)
>>>>>>> 14:03:02.760 INFO Unreachable member Member(address = akka.tcp://
>>>>>>> geyser@172.16.119.46:7000, status = Exiting)
>>>>>>> 14:03:04.843 INFO Adding member Member(address = akka.tcp://
>>>>>>> geyser@172.16.120.160:7000, status = Up)
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Ben
>>>>>>>
>>>>>>> --
>> >>>>>>>>>> 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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>
>
>
> --
>
> Patrik Nordwall
> Akka Tech Lead
> Lightbend <http://www.lightbend.com/> - Reactive apps on the JVM
> Twitter: @patriknw
>
> [image: Lightbend] <http://www.lightbend.com/>
>
> --
> >>>>>>>>>> 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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>
--
Cheers,
Konrad 'ktoso' Malawski
Akka <http://akka.io/> @ Lightbend <http://lightbend.com/>
--
>>>>>>>>>> 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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