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

[Richard Andrews]

--- Joel Reymont <joelr1@REDACTED> wrote:

> http://wagerlabs.com/archives/125.html
> 
> This is not for the faint-hearted!

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

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. If any report a problem then
resume on all nodes without changing code.

But OTP doesn't seem to have any way to pre-test if the code_change callback
implementation can support the current and desired versions.



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