Hi Tim,
I do think your recommendation in 3 & 4 makes a lot of sense and improves the 
usability of the API.  Given that Trove currently only supports a single 
datastore deployment per control system, does the current work also allow for a 
default type/version to be defined so that operators of Trove can set this as a 
property to maintain the current API compatibility/behavior?

Josh


From: Tim Simpson <tim.simp...@rackspace.com<mailto:tim.simp...@rackspace.com>>
Reply-To: OpenStack Development Mailing List 
<openstack-dev@lists.openstack.org<mailto:openstack-dev@lists.openstack.org>>
Date: Friday, October 18, 2013 2:30 PM
To: 
"openstack-dev@lists.openstack.org<mailto:openstack-dev@lists.openstack.org>" 
<openstack-dev@lists.openstack.org<mailto:openstack-dev@lists.openstack.org>>
Subject: [openstack-dev] [Trove] How users should specify a datastore type when 
creating an instance

Hello fellow Trovians,

There has been some good work recently to figure out a way to specify a 
specific datastore  when using Trove. This is essential to supporting multiple 
datastores from the same install of Trove.

I have an issue with some elements of the proposed solution though, so I 
decided I'd start a thread here so we could talk about it.

As a quick refresher, here is the blue print for this work (there are some 
gists ammended to the end but I figured the mailing list would be an easier 
venue for discussion):
https://wiki.openstack.org/wiki/Trove/trove-versions-types

One issue I have is with the way the instance create call will change to 
support different data stores. For example, here is the post call:

"""
{
      "instance" : {
      "flavorRef" : "2",
      "name" : "as",
      "datastore_type" : "e60153d4-8ac4-414a-ad58-fe2e0035704a",
      "datastore_version" : "94ed1f9f-6c1a-4d6e-87e9-04ecff37b64b",
      "volume" : { "size" : "1" }
    }
}
"""

1. I think since we have two fields in the instance object we should make a new 
object for datastore and avoid the name prefixing, like this:

"""
{
     "instance" : {
      "flavorRef" : "2",
      "name" : "as",
      "datastore": {
            "type" : "e60153d4-8ac4-414a-ad58-fe2e0035704a",
            "version" : "94ed1f9f-6c1a-4d6e-87e9-04ecff37b64b"
      }
      "volume" : { "size" : "1" }
    }
}
"""

2. I also think a datastore_version alone should be sufficient since the 
associated datastore type will be implied:

"""
{
      "instance" : {
      "flavorRef" : "2",
      "name" : "as",
      "datastore": {
            "version" : "94ed1f9f-6c1a-4d6e-87e9-04ecff37b64b"
      }
      "volume" : { "size" : "1" }
    }
}
"""

3. Additionally, while a datastore_type should have an ID in the Trove 
infastructure database, it should also be possible to pass just the name of the 
datastore type to the instance call, such as "mysql" or "mongo". Maybe we could 
allow this in addition to the ID? I think this form should actually use the 
argument "type", and the id should then be passed as "type_id" instead.

"""
{
      "instance" : {
      "flavorRef" : "2",
      "name" : "as",
      "datastore": {
            "type" : "mysql",
            "version" : "94ed1f9f-6c1a-4d6e-87e9-04ecff37b64b"
      }
      "volume" : { "size" : "1" }
    }
}

"""

4. Additionally, in the current pull request to implement this it is possible 
to avoid passing a version, but only if no more than one version of the 
datastore_type exists in the database.

I think instead the datastore_type row in the database should also have a 
"default_version_id" property, that an operator could update to the most recent 
version or whatever other criteria they wish to use, meaning the call could 
become this simple:

"""
{
      "instance" : {
      "flavorRef" : "2",
      "name" : "as",
      "datastore": {
            "type" : "mysql"
      }
      "volume" : { "size" : "1" }
    }
}
"""

Thoughts?

Thanks,

Tim
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