Odd company release cycle: Go Distributed Source Control?
- by MrLane
sorry about this long post, but I think it is worth it!
I have just started with a small .NET shop that operates quite a bit differently to other places that I have worked. Unlike any of my previous positions, the software written here is targetted at multiple customers and not every customer gets the latest release of the software at the same time. As such, there is no "current production version." When a customer does get an update, they also get all of the features added to he software since their last update, which could be a long time ago. The software is highly configurable and features can be turned on and off: so called "feature toggles." Release cycles are very tight here, in fact they are not on a shedule: when a feature is complete the software is deployed to the relevant customer.
The team only last year moved from Visual Source Safe to Team Foundation Server. The problem is they still use TFS as if it were VSS and enforce Checkout locks on a single code branch. Whenever a bug fix gets put out into the field (even for a single customer) they simply build whatever is in TFS, test the bug was fixed and deploy to the customer! (Myself coming from a pharma and medical devices software background this is unbeliveable!). The result is that half baked dev code gets put into production without being even tested. Bugs are always slipping into release builds, but often a customer who just got a build will not see these bugs if they don't use the feature the bug is in. The director knows this is a problem as the company is starting to grow all of a sudden with some big clients coming on board and more smaller ones.
I have been asked to look at source control options in order to eliminate deploying of buggy or unfinished code but to not sacrifice the somewhat asyncronous nature of the teams releases. I have used VSS, TFS, SVN and Bazaar in my career, but TFS is where most of my experience has been.
Previously most teams I have worked with use a two or three branch solution of Dev-Test-Prod, where for a month developers work directly in Dev and then changes are merged to Test then Prod, or promoted "when its done" rather than on a fixed cycle. Automated builds were used, using either Cruise Control or Team Build. In my previous job Bazaar was used sitting on top of SVN: devs worked in their own small feature branches then pushed their changes to SVN (which was tied into TeamCity). This was nice in that it was easy to isolate changes and share them with other peoples branches.
With both of these models there was a central dev and prod (and sometimes test) branch through which code was pushed (and labels were used to mark builds in prod from which releases were made...and these were made into branches for bug fixes to releases and merged back to dev). This doesn't really suit the way of working here, however: there is no order to when various features will be released, they get pushed when they are complete.
With this requirement the "continuous integration" approach as I see it breaks down. To get a new feature out with continuous integration it has to be pushed via dev-test-prod and that will capture any unfinished work in dev.
I am thinking that to overcome this we should go down a heavily feature branched model with NO dev-test-prod branches, rather the source should exist as a series of feature branches which when development work is complete are locked, tested, fixed, locked, tested and then released. Other feature branches can grab changes from other branches when they need/want, so eventually all changes get absorbed into everyone elses. This fits very much down a pure Bazaar model from what I experienced at my last job.
As flexible as this sounds it just seems odd to not have a dev trunk or prod branch somewhere, and I am worried about branches forking never to re-integrate, or small late changes made that never get pulled across to other branches and developers complaining about merge disasters...
What are peoples thoughts on this?
A second final question: I am somewhat confused about the exact definition of distributed source control: some people seem to suggest it is about just not having a central repository like TFS or SVN, some say it is about being disconnected (SVN is 90% disconnected and TFS has a perfectly functional offline mode) and others say it is about Feature Branching and ease of merging between branches with no parent-child relationship (TFS also has baseless merging!). Perhaps this is a second question!
