[OpenSIPS-Users] usrloc restart persistency on seed node

[John Quick]

Hi Liviu,

I like your suggestion. It seems like a pragmatic solution so I welcome this
idea.
The X second delay is probably unavoidable, but could there be a problem if
new registration requests arrive during the delay period?

I already have an X second delay because my current work-around is to launch
a background script just before starting OpenSIPS.
The background script has an X second delay then it runs "opensipsctl fifo
ul_cluster_sync" and then exits.

For backward compatibility, perhaps the default behaviour should be the same
as it is now.

John Quick
Smartvox Limited


> Happy New Year John, Alexey and everyone else!
>
> I just finished catching up with this thread, and I must admit that I now
> concur with John's distaste of the asymmetric nature of cluster node
restarts!
>
> Although it is correct and gets the job done, the 2.4 "seed" mechanism
forces
> the admin to conditionally add a "opensipsctl fifo ul_cluster_sync"
command
> into the startup script of all "seed" nodes.  I think we can do better :)
>
> What if we kept the "seed" concept, but tweaked it such that instead of 
> meaning:
> "following a restart, always start in 'synced' state, with an empty
dataset"
>
> ... it would now mean:
> "following a restart or cluster sync command, fall back to a 'synced'
state,
> with an empty dataset if and only if we are unable to find a suitable sync
> candidate within X seconds"
>
> This solution seems to fit all requirements that I've seen posted so far.
It is:
>
> * correct (a cluster with at least 1 "seed" node will still never
deadlock)
> * symmetric (with the exception of cluster bootstrapping, all node
restarts are identical)
> * autonomous (users need not even know about "ul_cluster_sync" anymore!  
> Not saying this is necessarily good, but it brings down the learning
curve)
>
> The only downside could be that any cluster bootstrap will now last at 
> least X seconds.
> But that seems such a rare event (in production, at least) that we need 
> not worry about it.  Furthermore, the X seconds will be configurable.
>
> What do you think?
>
> PS: by "cluster bootstrap" I mean (re)starting all nodes simultaneously.
>
> Best regards,
>
> Liviu Chircu
> OpenSIPS Developer
> http://www.opensips-solutions.com