We did consider doing that, but decided it wasn't really any different from the 
other options as it required the deployer to know to alter that data.  That 
would require the fewest code changes, though.  It was also my understanding 
that mysql variants were a possibility as well (percona and mariadb), which is 
what brought on the objection to just defaulting in code.  Also, we can't 
derive the version being used, so we *could* fill it with a dummy version and 
assume mysql, but I don't feel like that solves the problem or the objections 
to the earlier solutions.  And then we also have bogus data in the database.

Since there's no perfect solution, I'm really just hoping to gather consensus 
among people who are running existing trove installations and have yet to 
upgrade to the newer code about what would be easiest for them.  My 
understanding is that list is basically HP and Rackspace, and maybe Ebay?, but 
the hope was that bringing the issue up on the list might confirm or refute 
that assumption and drive the conversation to a suitable workaround for those 
affected, which hopefully isn't that many organizations at this point.

The options are basically:

1. Put the onus on the deployer to correct existing records in the database.
2. Have the migration script put dummy data in the database which you have to 
3. Put the onus on the deployer to fill out values in the config value


On Dec 18, 2013, at 8:46 PM, Robert Myers 
<myer0...@gmail.com<mailto:myer0...@gmail.com>> wrote:

There is the database migration for datastores. We should add a function to  
back fill the existing data with either a dummy data or set it to 'mysql' as 
that was the only possibility before data stores.

On Dec 18, 2013 3:23 PM, "Greg Hill" 
<greg.h...@rackspace.com<mailto:greg.h...@rackspace.com>> wrote:
I've been working on fixing a bug related to migrating existing installations 
to the new datastore code:


The basic gist is that existing instances won't have any data in the 
datastore_version_id field in the database unless we somehow populate that data 
during migration, and not having that data populated breaks a lot of things 
(including the ability to list instances or delete or resize old instances).  
It's impossible to populate that data in an automatic, generic way, since it's 
highly vendor-dependent on what database and version they currently support, 
and there's not enough data in the older schema to populate the new tables 

So far, we've come up with some non-optimal solutions:

1. The first iteration was to assume 'mysql' as the database manager on 
instances without a datastore set.
2. The next iteration was to make the default value be configurable in 
trove.conf, but default to 'mysql' if it wasn't set.
3. It was then proposed that we could just use the 'default_datastore' value 
from the config, which may or may not be set by the operator.

My problem with any of these approaches beyond the first is that requiring 
people to populate config values in order to successfully migrate to the newer 
code is really no different than requiring them to populate the new database 
tables with appropriate data and updating the existing instances with the 
appropriate values.  Either way, it's now highly dependent on people deploying 
the upgrade to know about this change and react accordingly.

Does anyone have a better solution that we aren't considering?  Is this even 
worth the effort given that trove has so few current deployments that we can 
just make sure everyone is populating the new tables as part of their upgrade 
path and not bother fixing the code to deal with the legacy data?


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