[p4] Codelines and Components

David Ferguson daf at vmware.com
Thu Nov 20 11:52:12 PST 2008


My objection to the //depot/main/component is fundamentally one of branching expectations.  That policy tends to drive people toward branching all components every time any of them branch.  With a //depot/component/<branch>/... Model, the likelihood that individual components will soon have their own release schedule and branching models is far greater. 

An individual release schedule for each component promotes cleaner interfaces and abstraction.  When all components branch together, the seduction of simplistic integrations is pretty successful.  Using independent chunks of code helps isolate a component and ensure formally defined interfaces since they never know who is going to consume them when. 

However, my viewpoint considers each component to be a fairly large, often separately developed, piece of major functionality.  If you're working with a small team or lots of small tightly coupled components, then I would agree with Matt.  Just don't stay there too long as you grow.  At a certain point, switching to the other model can become both technically and politically impossible.

-daf


> -----Original Message-----
> From: perforce-user-bounces at perforce.com 
> [mailto:perforce-user-bounces at perforce.com] On Behalf Of Matt 
> Craighead
> Sent: Thursday, November 20, 2008 10:58 AM
> To: Chris Helck
> Cc: perforce-user at perforce.com
> Subject: Re: [p4] Codelines and Components
> 
> This is the "//depot/component/main/..." vs. 
> "//depot/main/component/..."
> debate.
> 
> I favor the latter approach -- put all components under a 
> shared "main".
> The key advantages:
> 
> - You can use relative paths to find one component from another.
> - You can modify the interfaces between components in a 
> single atomic commit to the depot.
> - Bug fixes and other enhancements to components are picked 
> up immediately, without need to cut a new release.
> - Changes don't affect other branches.  Changing 
> //depot/releaseX will not affect *anything* in //depot/main.
> 
> The biggest downside is that new bugs in components are also 
> picked up immediately.  But discovering a bug sooner (and 
> being forced to fix it
> sooner) is usually a good thing, not a bad thing.  And if you 
> have good regression tests, you can prevent most breaks from 
> happening in the first place using a product such as my 
> company's Cascade, which will not only automate your builds 
> and regression tests, but will also refuse to allow people to 
> commit changes that haven't passed those build and regression tests.
> 
> 
> On Tue, Nov 18, 2008 at 4:27 PM, Chris Helck 
> <Chris.Helck at us.icap.com>wrote:
> 
> > I'm looking for tips and references on how to work with multiple 
> > components and codelines. We're a small Java shop and we 
> use Maven to 
> > build components (jar files). We're having problems when a single 
> > functional change involves changes to multiple components. 
> Issues of 
> > which codelines to modify, when to propagate changes, and 
> who should 
> > compile against what are always popping up.
> >
> > For example, should an application's mainline always compile/link 
> > against its dependent component mainlines? Or should 
> dependencies be 
> > always to release lines?
> >
> > Another example: if while doing a large change in a development 
> > codeline I discover a small, but nasty, bug in another component. 
> > Should I create a development branch for the component and fix the 
> > bug, or should I fix the bug on its mainline (or even in a 
> release line)?
> >
> > While we're enchanted by the promise of components we're 
> finding it to 
> > be a very confusing landscape to navigate through.
> >
> > Regards,
> > Christopher Helck
> >
> > 
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> --
> Matt Craighead
> Founder/CEO, Conifer Systems LLC
> http://www.conifersystems.com
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