pkg rollback

[Arto Pekkanen]

Why does not ZFS snapshot and rollback work for this scenario?

On 7.6.2017 16:40, Luca Pizzamiglio wrote:
> Hi all,
> 
> I'm trying to figure out how an automatic process to upgrade packages
> on production machines can look like.
> 
> A kind of:
> # pkg upgrade
> # restart services
> # if everything not OK
> #   rollback
> #   restart services
> 
> I'm considering a package repository that is not guaranteeing 100%
> stability, like `latest`.
> Even intercepting events needing manual intervention (i.e. reported by
> UPDATING), a blind pkg upgrade can break the web application running
> on top.
> So, I was thinking if it's possible to perform some kind of rollback.
> 
> to proof if it's possible, I wrote a shell scripts with two features
> (it helped me a lot to understand how pkg works):
> # backup
> ## backup the repo sqlite database
> ## run `pkg update` and determine all actions would be performed by
> `pkg upgrade` (a kind of `pkg upgrade` simulation)
> ## backup all packages from the cache that would be replaced by `pkg upgrade`
> ## download all new packages to determine potentially conflicts
> ## backup all packages from the cache that would be replaced by `pkg
> upgrade` (after determined conflicts)
> ## restore the repo sqlite database
> # rollback
> ## restore the repo sqlite database
> ## install all previously backup'ed packages
> 
> Another approach, less complex, but I guess even valid, could be:
> # backup (or snapshot)
> ## backup of the repo sqlite database
> ## take a snapshot of all installed packages
> # rollback (a previously stored snapshot)
> ## restore the repo sqlite database
> ## reinstall all previously backup'ed packages
> 
> Adding two features [snapshot and rollback] to pkg(8), the automated
> upgrade process would become:
> # pkg snapshot
> # pkg upgrade
> # restart services
> # if everything not OK
> #   rollback
> #   restart services
> 
> What do you think?
> What am I missing?
> Ideas, suggestions and feedback are welcome, so, please, feel free to reply.
> 
> Best regards,
> Luca
> 
> PS: I'd use `pkg snapshot`, because `pkg backup` already exist and it
> has another meaning.
> PS2: In some case, `zfs snapshot` could work as well, but it's not
> always possible
> PS3: if feebacks are positive, I'd like to implement those features
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-- 
Arto Pekkanen

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