[teiid-designer-dev] [teiid-dev] VDB Versioning Feature

Mon Feb 8 13:42:17 EST 2010

What Ted is getting into here is physical limitations in the container
world. Since all the VDBs are stored on file system, you can not have
two same named files in same directory. This is no different form
earlier versions of Teiid (not MMx as it used DBMS for storage). Having
separately named files with same VDB name in the 'ConfigurationInfo.def'
file is still possible. If this necessary we could work with tooling to
include the version number on the vdb file going forward.

But we *can not* support the automatic version of the VDB. This needs to
be a explicit exercise from the user by defining the version info in the
'ConfigurationInfo.def' file before he/she deploys it.

On Mon, 2010-02-08 at 13:28 -0500, Ted Jones wrote:
> It seems to me that we are somewhat limited in what we can support from the previous deployment model as compared to what we can do in a container environment. Think of other deployment models in the container world (e.g. wars, ears, connectors, etc.).  There is no concept of multiple versions for anything else in a container, right? The file to be deployed has to be renamed in order to not overwrite the existing deployment. I'm not saying we couldn't add the smarts to make this work, but it would be fugly and unconventional in our new container world.
> 
> The version field may still prove valuable as a property to indicate the version of the deployed vdb, but only one version would/could ever be deployed at one time.
> 
> Again I should mention that deploying two versions of the same VDB (same file name) and having them co-exist in the same container is not possible in Jopr/JON and that is due to the restrictions of the container's deployment paradigm.
> 
> Ted 
> 
> ----- Original Message -----
> From: "Barry Lafond" <blafond at redhat.com>
> To: "teiid-designer-dev" <teiid-designer-dev at lists.jboss.org>, "teiid-dev" <teiid-dev at lists.jboss.org>
> Sent: Monday, February 8, 2010 11:58:24 AM GMT -06:00 US/Canada Central
> Subject: Re: [teiid-dev] [teiid-designer-dev]  VDB Versioning Feature
> 
> 
> 
> (NOTE: Posted for Mike Walker. Can't get into the list admin right now to accept his post) 
> 
> I agree with Ken's comments. This is a simple but extremely valuable 
> feature that emerged from a customer request. I took advantage of it 
> at a separate customer just last week. And the default behavior is 
> quite intuitive - the most recent version is the default, by default. 
> Have we had users or customers complain that this is confusing? If so, 
> then maybe docs or usability could be improved, but please don't 
> remove the feature, customers waited years for it. 
> 
> Mike 
> 
> ----- Original Message ----- 
> From: "Ken Johnson" <kejohnso at redhat.com> 
> To: "Ramesh Reddy" <rareddy at redhat.com> 
> Cc: teiid-designer-dev at lists.jboss.org, teiid-dev at lists.jboss.org 
> Sent: Monday, February 8, 2010 10:37:37 AM GMT -06:00 US/Canada Central 
> Subject: Re: [teiid-designer-dev] [teiid-dev] VDB Versioning Feature 
> 
> I believe some of the characterizations below paint an overly negative 
> view of the current versioning capabilities. These are generally 
> regarded by users as valuable and with the relatively new "default 
> version" property very flexible. More inline. 
> Ramesh Reddy wrote: 
> > In Teiid a VDB is always represented by its name and version. Together 
> > they both represented a unique name for VDB. Although a version 
> > represents a particular schema version, 
> > 
> > 1) It is considered as a entirely different schema then that of the 
> > original VDB inside the Teiid runtime. 
> > 
> True, from a runtime standpoint, Teiid doesn't distinguish a new vdb 
> from a new version of an existing vdb. It's just another vdb. 
> 
> > 2) Usually version numbers are presented in the repository systems with 
> > implicit rollback behavior. Teiid gives no such rollback functionality. 
> > 
> Repository is somewhat orthogonal here. While users sometimes deploy 
> from a repository, the active VDB version is distinct from the 
> repository version if the repo is indeed being used at all. Currently, 
> there is a roll-back capability in that a later version of a deployed 
> vdb can be deactivated and connections revert back to the previous 
> version (or the new default version if the default property is being used). 
> 
> > 3) Confusion with automatic version upgrade. If a new VDB with same name 
> > is deployed, then version on this VDB is upgraded to next numerical 
> > number. The user does not even know what that version number is until 
> > they use some tool to figure out which version number that VDB is 
> > deployed under. This creates confusion. 
> > 
> This is not confusing, it's beneficial. For client apps that don't need 
> to know about a later version, they are not forced to change. This is 
> particularly important for minor, non-breaking changes. Client 
> applications should not be required to change simply because of a 
> version bump in the vdb. Client app changes are highly disruptive in an 
> organization - even replacing a JDBC client JAR that does not require 
> app code changes often needs layers of approval and test cycles. 
> 
> 
> > 4) If there are multiple VDB with different version numbers deployed in 
> > runtime and client is connecting with no explicit version number, then 
> > Teiid connects to "latest" or a VDB at "default" level. This again seems 
> > magical than honoring the explicit behavior. 
> > 
> This "magic" is good. Clients *can* be explicit if desired but do not 
> *have to* be explicit. Very powerful. 
> 
> > 5) Schema version is generally not supported by any RDBMS vendors. 
> > 
> True but IMHO this is not a reason to drop the feature. Teiid, though 
> like a RDBMS in many ways is not a RDBMS. 
> 
> > 6) In MMx product line this meant to represent the metadata repository 
> > version, but Teiid no longer has this concept. 
> > 
> This is not correct. the version is disconnected from the repository 
> entirely. It is simply a deployed version number. 
> 
> > 7) It was a way to move production users from one version of the VDB to 
> > another with out interruptions. In our opinion, this is more for the 
> > development environments than prod. 
> > 
> Agree this will be more common in pre-production, particularly staging 
> environments due to the level of dynamism. However that does not mean 
> it's exclusive to pre-production. 
> > so, we would like to propose to remove this "version" feature from 
> > Teiid. If users want they can manage the this through explicit VDB 
> > names. 
> > 
> I disagree with this proposal as it will tighten the coupling between 
> client applications and vdbs and take away a layer of indirection and 
> flexibility that's valuable at the data services layer. 
> > Please let us know if you think this feature is worth keeping and why? 
> > 
> I do! 
> 
> 
> > Thanks 
> > 
> > Ramesh.. 
> > 
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> > 
> 
> 