Multi-Configuration Projects

A multi-configuration project is useful for instances where your builds will make many similar build steps, and you would otherwise be duplicating steps.

As of 1.561, in Matrix Project Plugin.

Configuration matrix

The Configuration Matrix allows you to specify what steps to duplicate, and create a multiple-axis graph of the type of builds to create.

For example, let us say that we have a build that we want to create for several different targets alpha, beta, and we want to produce both debug and release outputs. With a freestyle job, we would have the following ant commands:

Ant: set-target-alpha debug compile
Ant: set-target-beta debug compile
Ant: set-target-gamma debug compile
Ant: set-target-alpha release compile
Ant: set-target-beta release compile
Ant: set-target-gamma release compile

We can reduce this to one ant target using variables:

Ant: $target $releasetype compile

And by adding two User Defined Axis in the Configuration Matrix:

Name: target
Value: set-target-alpha set-target-beta set-target-gamma

Name: releasetype
Value: debug release

The Names target and releasetype are exposed to the ant scripts as environment variables. The Value is a space delimited list of points to iterate through for each axis.

The immediate upshot is that if we have another release type to add (for example, debug-optimized), we can simply add the value to the releasetype user defined axis rather. The single change will add configuration to build the debug-optimized release type against all three values of target.

Misc

NOTE: you have to choose "Build multi-configuration project" when creating a project, it can not be changed later. If you skip this step, you will be very confused and not get very far.

Some links explaining this feature a bit more:

Newbie Note: Each configuration is akin to an individual job.  It has its own build history, logs, environment, etc. The history of your multi-config job only shows you a list of configurations executed. You have to drill into each configuration to see the history and console logs.

Executors used by a multi-configuration project

Reference: Re: Will a multi-configuration / matrix job always use up one executor on the master?

A matrix build project (that uses the Slave axis) will use one additional executor ("master executor"?) on a random node to coordinate the executions on the nodes defined by the Slave axis.
This executor is added as a temporary executor(also called as "flyweight task") to the node and does not use up a configured executor slot on this node (this behavior is controlled by hudson.model.Hudson.flyweightSupport). Only this "master executor" or "flyweight task" will be affected by the "Restrict where this project can be run" option, under Advanced Project Options. "Actual" or non-flyweight build execution can be controlled with the "Slaves" axis that can be added under the project's Configuration Matrix: individual nodes and/or labels containing multiple nodes can be selected, as well as filtering axis combinations.

You can also control which nodes can run flyweight tasks using the Exclude flyweight tasks plugin, or you can pin the flyweight executor to a specific node using the Matrix Tie Parent Plugin 

Configuration Matrix