[Engine-devel] Introducing virt / gluster flags at cluster level

[Ayal Baron]

----- Original Message -----
> On 03/04/2012 03:22 PM, Ayal Baron wrote:
> >
> >
> > ----- Original Message -----
> >>
> >>
> >> ----- Original Message -----
> >>> From: "Moti Asayag"<masayag at redhat.com>
> >>> To: engine-devel at ovirt.org
> >>> Sent: Sunday, March 4, 2012 12:20:43 PM
> >>> Subject: Re: [Engine-devel] Introducing virt / gluster flags at
> >>> cluster level
> >>>
> >>> On 03/01/2012 12:54 PM, Shireesh Anjal wrote:
> >>>> Hi,
> >>>>
> >>>> In order to identify whether a cluster exposes Gluster /
> >>>> Virtualization
> >>>> capabilities, we plan to introduce two boolean columns -
> >>>> virt_service
> >>>> and gluster_service in the vds_groups table. As per immediate
> >>>> plans, it
> >>>> is intended to support only one service per cluster, meaning
> >>>> only
> >>>> one of
> >>>> these two values can be true.
> >>>
> >>> Couldn't there be additional future services in the future ? In
> >>> that
> >>> case perhaps worth considering enum for services, to be stored in
> >>> a
> >>> single service column, its values are: virt, gluster,...) instead
> >>> of
> >>> extending the vds_group table consistently when introducing new
> >>> services
> >>> (under the assumption no mix of services is allowed).
> >>
> >> +1 for an Enum insteand of boolean columns. we have too much of
> >> that
> >> already and eventually we see long records and
> >>   routine refactoring to our DAL.
> >> Also to make mixed configuration we can embrace bit fields which
> >> interacts very nice with Enums e.g a 5 value of  is a cluster with
> >> VIRT(1) and FUTURE(4) capabilities
> >
> > I agree about the columns being inflexible but personally I don't
> > like enums.  What if we need to support finer grained services?
> > e.g. different topologies (active/passive, active/active etc) or
> > other types of intricate relationships?
> > Not to mention that looking at the raw data you don't undetstand
> > what it means without holding a dictionary.  And it's annoying to
> > support BC of the numbers once things change.
> 
> enums are an issue, since we want to share them.
> i agree services table seems the right approach, but actually,
> booleans
> are used here exactly because it seems services is the right long
> term
> approach, but we there is a lot of ground to cover before we know how
> they would look like.
> so boolean flags for the first few services, learning from these,
> designing the bigger service models, and upgrading to it from the
> cluster-with-flags seems (to me) the right path to take.

db scheme should be something that doesn't change every major, minor and z-stream version.  It means we're doing something wrong.
Having a 'gluster service' boolean column means that by definition we will be changing the db scheme for the next service we want to add or even for the same service but when we'll need some more info.
To start with, we can just rely on the hosts themselves reporting capabilities and we can cache this info if we want it to display quickly next time we load.  This would be similar to supported cpu types.
If we have limitations on combining services then the first service utilized wins.



> 
> >
> >
> >>
> >>>
> >>>>
> >>>> We plan to make following changes as part of the patch:
> >>>>
> >>>> 1) Introduce an upgrade script for adding following columns to
> >>>> the
> >>>> table
> >>>> "vds_groups"
> >>>>      - virt_service - boolean - NOT_NULL - default value true
> >>>>      - gluster_service - boolean - NOT_NULL - default value
> >>>>      false
> >>>>
> >>>> =>  What is the naming convention for naming the upgrade script?
> >>>> Is
> >>>> it
> >>>> <major-version>_<minor-version>_<running-sequence-with-step-10>_script_description.sql
> >>>> ? By that logic, the name of our script will be something like
> >>>> 03_01_0560_add_service_columns_to_vds_groups.sql
> >>>
> >>> Correct. Make sure to verify script sequence uniqueness (under
> >>> ovirt-engine/backend/manager/dbscripts/upgrade) before pushing,
> >>> since
> >>> there is no enforcement for that.
> >>>
> >>>>
> >>>> 2) Modify vds_groups_sp.sql to introduce these arguments /
> >>>> variables in
> >>>> save and update methods
> >>>>
> >>>> 3) Modify the DAO interface and implementation to introduce
> >>>> these
> >>>> arguments / variables in the save/update methods and
> >>>> VdsGroupRawMapper.
> >>>>
> >>>> 4) Modify the DAO JUnit test class to take care of these new
> >>>> fields, if
> >>>> required.
> >>>
> >>> As part of DAO unit-test you should add the new columns and
> >>> possible
> >>> data to
> >>> ovirt-engine/backend/manager/modules/dal/src/test/resources/fixtures.xml
> >>>
> >>>>
> >>>> 5) Modify class VDSGroup to introduce the two new boolean
> >>>> variables
> >>>> virtService and glusterService and modify the methods equals and
> >>>> hashCode to use these.
> >>>>
> >>>> =>  One question here. Most of the attributes of class VDSGroup
> >>>> have
> >>>> annotations like @XmlElement and @Column. I think these are
> >>>> related
> >>>> to
> >>>> jaxb and JPA. Are these annotations really required? If yes, how
> >>>> are
> >>>> they useful?
> >>>>
> >>>
> >>> @XmlElement annotations could be deleted from that file as a
> >>> prior
> >>> patch
> >>> to the patch-set.
> >>>
> >>> JPA annotations could be ignored as not fully supported nor
> >>> maintained.
> >>>
> >>>> 6) REST API : Default populate these variables (virtService =
> >>>> true,
> >>>> glusterService = false) before invoking the BLL command
> >>>> (AddVdsGroupCommand / UpdateVdsGroupCommand). This makes sure
> >>>> that
> >>>> the
> >>>> existing API won't break. No change in api.xsd for now.
> >>>>
> >>>> 7) webadmin create cluster code: Default populate the new
> >>>> variables,
> >>>> same as above. No change in UI screen for now.
> >>>>
> >>>> =>  Alternatively, the variable declaration on VDSGroup itself
> >>>> can
> >>>> initialize these variables with default values, so that changes
> >>>> to
> >>>> UI /
> >>>> REST API code (points 6 and 7) may not be required immediately.
> >>>> What do
> >>>> you suggest?
> >>>>
> >>>> Inputs / comments / suggestions welcome.
> >>>>
> >>>
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> >>>
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