[erlang-questions] Upgrading Erlang clusters for fun and profit

Joel Reymont <>
Mon Oct 15 10:40:00 CEST 2007

On Oct 15, 2007, at 7:28 AM, Richard Andrews wrote:

> There was no mention of where code_change() fits into the process.

It doesn't. It's not necessary when upgrading app-by-app and not all  
the processes suspended and restarted would be gen_servers.

> I immediately thought that a two-phase commit would be useful:  
> phase 1 to
> suspend and test if the upgrade is supported; and if all nodes say  
> ok, then
> perform phase 2 to load the new code on all nodes.

It's better to do a rolling upgrade, I think, node by node. It avoids  
taking your whole cluster out of service.


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