A strategy for Integrations versions with maven…

We are currently asking ourselves at INNOVEO, if we need to keep a version of integration versions.
Integration versions main objective is to be integrated with other modules to make and test an
application or a framework. This question is quickly becoming essential when working with several
modules, where you will have to to rely on intermediate, non finalized versions of modules.

Since we are also following  the continuous integration paradigm for all our modules, Thanks to
Apache MAVEN, these integration versions are produced by a continuous integration server
(Team City from JetBrain), very frequently.

So, how can you deal with these, possibly numerous, integration versions? The response is coming
from this extract from IVY documentation

There are basically two ways to deal with them,

Use a naming convention
The idea is pretty simple, each time you publish a new integration of your module you give the same
name to the version (in #maven world this is for example 1.0-SNAPSHOT). The dependency manager
should then be aware that this version is special because it changes over time, so that it does not
trust its local cache if it already has the version, but check the date of the version on the repository
and see if it has changed.

Create automatically a new version for each
in this case you use either a build number or a timestamp to publish each new integration version
with a new version name. Then you can use one of the numerous ways in Ivy to express a version
constraint. Usually selecting the very latest one (using ‘latest.integration’ as version constraint) is
enough.

But usually we recommend to use the second one, because using a new version each time you publish
a new version better fits the version identity paradigm, and can make all your builds reproducible,
even integration one. And this is interesting because it enables, with some work in your build system,
to introduce a mechanism to promote an integration build to a more stable status, like a milestone
or a release.

The example given is very interesting…

Imagine you have a customer which comes on a Monday morning and asks your latest version of your
software, for testing or demonstration purpose. Obviously he needs it for the afternoon 🙂 Now if
you have a continuous integration process and a good tracking of your changes and your artifacts, it
may occur that you are actually able to fulfill his request without needing the use of a dolorean to
give you some more time 🙂 But it may occur also that your latest version stable enough to be used
for the purpose of the customer was actually built a few days ago, because the very latest just break
a feature or introduce a new one you don’t want to deliver. In this case, you can deliver this ‘stable’
integration build if you want, but be sure that a few days, or weeks, or even months later, the
customer will ask for a bug fix on this demo only version. Why? Because it’s a customer, and we
all know how they are 🙂

So, with a build promotion feature of any build in your repository, the solution would be pretty easy:
when the customer ask for the version, you not only deliver the integration build, but you also
promote it to a milestone status, for example. this promotion indicates that you should keep track of
this version in a long period, to be able to come back to it and create a branch if needed.

Note this is the strategy at #Eclipse.org, where a nightly build (N20080420) can be promoted to an Maintenance
release if quality is good enough. Below I’ve put an extract of a presentation document from © 2006 by Alex Blewitt;
made available under the EPL v1.0 |  2006-03-20  |  http://www.rcpapps.org/

We are now using the same naming convention at INNOVEO for our product

Eclipse builds are of different type:

(N) Nightly	Built every night (whether successful or not) Used to run quality metrics and whether tests have passed
(I) Integration	Used to ensure that code works together Used to run quality metrics
(M) Maintenance	Released at the end of each build cycle
(R) Release	Released at the end of each release cycle

Each product is given a build id,

• Build Type (N, I, M or R)
• Build ID (M20060118)
• Build Label (M20060118-1600)
• Timestamp of build (16:00 on the 18th Jan, 2006)
• Each release corresponds to a specific build label
• May also be known as other aliases in CVS
• R3_1_2, vI20060118-1000, R3_1_Maintenance

To keep the #Eclipse ecosystem in step, everything is tagged

• Part of the build process tags the current code with vI20060320
• A build is only promoted from N->I if there are no build failures
• A build is promoted from I->M if there are no failures and all the
  functionality works to a satisfactory level
• A build is promoted from M->R at the end of a release cycle and
  the quality is suitably high

On the other hand, the main drawback of this solution is that it can produce a lot of intermediate
versions, and you will have to run some cleaning scripts in your repository…

I will present You later how you can achieve this goal with MAVEN and Team City