Indeed. This is the relevant bit of docs I believe
(http://doc.akka.io/docs/akka/2.4.17/common/cluster.html#Membership):
The node identifier internally also contains a UID that uniquely
identifies this actor system instance at thathostname:port. Akka uses
the UID to be able to reliably trigger remote death watch. This means
that the same actor system can never join a cluster again once it's
been removed from that cluster. To re-join an actor system with the
samehostname:portto a cluster you have to stop the actor system and
start a new one with the samehostname:portwhich will then receive a
differentUID.
After re-starting the node it will get a new UID and will be considered
a new member.
The unreachable member (the previous incarnation of your node) needs to
be downed first for new members to be admitted by the leader.
Cheers,
Michal
On 04/04/17 08:58, Viktor Klang wrote:
No, it needs to be Downed.
On Tue, Apr 4, 2017 at 9:50 AM, Unmesh Joshi <[email protected]
<mailto:[email protected]>> wrote:
Hi,
If I restart the crashed node on same host and port, it should be
reachable now and consensus should be reached isnt it?
Thanks,
Unmesh
On Tuesday, 4 April 2017 13:09:22 UTC+5:30, Michal Borowiecki wrote:
Hi Unmesh,
AFAIK, the crashed node has to be downed (whether manually or
automatically) for the cluster to reach convergence.
Only once there are no unreachable nodes observed by any
member can the leader resume it's duties and allow the new
member (your re-started instance) to join.
For testing & dev, you can use auto-downing. For production
you need to choose a more resilient approach I'm afraid, as
out of the box auto-downing doesn't provide a way to address
the split-brain-problem which most likely would bite you in a
real life environment sooner or later.
Cheers,
Michal
On 04/04/17 08:31, Unmesh Joshi wrote:
Is it possibly because in a two node cluster, there can never
be majority ( > 50%) nodes agreeing on membership to mark a
node as 'seen'?
On Tuesday, 4 April 2017 12:46:17 UTC+5:30, Unmesh Joshi wrote:
Hi,
I have a two node cluster in a cluster. If I crash one of
the nodes (*10.131.22.26:3552
<http://10.131.22.26:3552>), *and bring it up again, I
start getting following messages from other nodes. Now
that the node is reachable and there are only two nodes
in the cluster, why should it give following message with
seen=false for 1*0.131.22.26:3552
<http://0.131.22.26:3552>? *
For members to be seen, is there any other configuration
that needs to be tuned?
[INFO] [04/04/2017 12:38:49.623]
[csw-cluster-akka.actor.default-dispatcher-14]
[akka.cluster.Cluster(akka://csw-cluster)] Cluster
Node [akka.tcp://[email protected]:41574
<http://[email protected]:41574>] - Leader can
currently not perform its duties, reachability
status: [akka.tcp://[email protected]:41574
<http://[email protected]:41574> ->
akka.tcp://[email protected]:3552
<http://[email protected]:3552>: Unreachable
[Unreachable] (1)], member status:
[akka.tcp://[email protected]:3552
<http://[email protected]:3552> Up seen=false,
akka.tcp://[email protected]:41574
<http://[email protected]:41574> Up seen=true]
[INFO] [04/04/2017 12:39:49.634]
[csw-cluster-akka.actor.default-dispatcher-2]
[akka.cluster.Cluster(akka://csw-cluster)] Cluster
Node [akka.tcp://[email protected]:41574
<http://[email protected]:41574>] - Leader can
currently not perform its duties, reachability
status: [akka.tcp://[email protected]:41574
<http://[email protected]:41574> ->
akka.tcp://[email protected]:3552
<http://[email protected]:3552>: Unreachable
[Unreachable] (1)], member
status:*[akka.tcp://[email protected]:3552
<http://[email protected]:3552> Up
seen=false*,
akka.tcp://[email protected]:41574
<http://[email protected]:41574> Up seen=true]
[INFO] [04/04/2017 12:40:49.632]
[csw-cluster-akka.actor.default-dispatcher-17]
[akka.cluster.Cluster(akka://csw-cluster)] Cluster
Node [akka.tcp://[email protected]:41574
<http://[email protected]:41574>] - Leader can
currently not perform its duties, reachability
status: [akka.t
Thanks,
Unmesh
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