Re: [jgroups-users] problem with cluster merge after startup user error

On 09/04/18 16:18, Questions/problems related to using JGroups wrote:

> Thanks. That's good to know it's possible, and now I'll be wondering if 
> there's any way to know that startup is actually done.

You could send a DONE message, but if the cluster doesn't form, that's 
useless as noone will receive it...

> At this last part, just wondering if I can speed up how often the 
> discovery signal is sent out (assuming it doesn't affect anything else). 

Not the discovery signal, but the frequency at which MERGE3 triggers it. 
(Note that discovery is only needed if the transport is not UDP!):

MERGE3 merge=ch.getProtocolStack().findProtocol(MERGE3.class);
merge.setValue("check_interval", 5000); // reduces the time to check for 
inconsistencies


merge.sendInfo();
// this sends an INFO message to all 'reachable' members; on TCP it uses 
discovery

The sendInfo() method sends the view-id to all 'reachable' members. 
Every member then checks for inconsistencies and triggers a merge if needed.


> In my tests, I started A, then B (with wrong info), and it was between 
> 50-90 seconds before the two clusters merged. That's enough time for the 
> user to see that they have two clusters instead of one, start looking at 
> the manual again or start an email to support, and then unexpectedly (to 
> the user) the clusters join and things are correct. Not a big problem 
> though -- we log the initial_hosts info so it will be clear from logs if 
> someone hits this and complains.
> 
> Thanks for the help. Checking for MergeView I think will clean up the 
> internal issues we have if two coordinators start instead of one 
> coordinator and other nodes join.

Right - I still think that there may be a much better solution lurking ...

> Cheers,
> Bobby
> 
> 
> 
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-- 
Bela Ban | http://www.jgroups.org


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