Apache Karaf feature prerequisite - osgi

Question

Karaf 4.0.3
I have the following pseudo-feature:
<features name="my-feature" xmlns="http://karaf.apache.org/xmlns/features/v1.3.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://karaf.apache.org/xmlns/features/v1.3.0 http://karaf.apache.org/xmlns/features/v1.3.0">
<feature name="C" version="${project.version}" start-level="25" install="auto">
<bundle start-level="25">...BundleC1...</bundle>
</feature>
<feature name="A" version="${project.version}" start-level="30" install="auto">
<feature prerequisite="true">C</feature>
<bundle start-level="30">...BundleA1...</bundle>
</feature>
<feature name="B" version="${project.version}" start-level="35" install="auto">
<feature prerequisite="true">C</feature>
<bundle start-level="35">...BundleB1...</bundle>
</feature>
C is independant
A depends on C
B depends on C
In this example the bundle 'BundleB1' imports wrong major version of 'BundleC1' and we get the "missing requirement" error (as expected). However if I log into the karaf console and run 'feature:list' I will see that C is Started, A is Uninstalled and B is Uninstalled.
I expect A to be Started since it only has dependencies to C. A will start fine if I comment out the entire C feature or if I afterwards run feature:install A
If I put each of these three features in seperate feature.xml files I get the expected outcome of C+A as Started and B as Uninstalled.
What am I doing wrong?
Am I misunderstanding how the prerequisite attribute works? As a sidenote, if I skip the prerequisite attribute all together then no feature will get installed whatsover...

Answer 1

This is the expected behavior in Karaf 4 : Karaf creates one subsystem with all the features to install. This subsystem is resolved in one pass : either it success or it fails, as a whole.
The prerequisite attribute tells Karaf to install this feature in an independent subsystem : All the bundles are installed and started before trying to resolve the others features.
In your case :
C is installed/started ;
A+B is resolved, but it fails