OSGi caches leaves newly installed bundles in INSTALLED state - osgi

Question

I have a C++ program that loads a JVM and launches an OSGi framework. The OSGi framework is Equinox, more precisely org.eclipse.osgi_3.8.1.v20120830-144521.jar.
The Launcher
The OSGi launcher is called from C++ using JNI and it goes like this (details left out for brevity):
// Create OSGi framework.
final ServiceLoader<FrameworkFactory> frameworkFactoryLoader =
ServiceLoader.load(FrameworkFactory.class);
final FrameworkFactory frameworkFactory =
getFrameworkFactory(frameworkFactoryLoader);
final Map<String, String> osgiConfig = ...
final Framework osgiFramework = frameworkFactory.newFramework(osgiConfig);
// Start the framework.
osgiFramework.start();
// Install some bundles.
final BundleContext frameworkBundleContext = osgiFramework.getBundleContext();
final Bundle bundle1 =
installBundle(frameworkBundleContext, "reference:" + bundle1URI, null);
installBundle(frameworkBundleContext, "reference:" + bundle2URI, 5);
installBundle(frameworkBundleContext, "reference:" + bundle3URI, 10);
...
// Explicitly starting a particular bundle.
bundle1.start();
...
// Raise the framework start level so bundles are started
// at the desired start levels.
final FrameworkStartLevel frameworkStartLevelObject =
bundleAdapt(systemBundle, FrameworkStartLevel.class);
frameworkStartLevelObject.setStartLevel(10, ...left-out...);
The helper function for installing a bundle goes like this:
private Bundle installBundle(final BundleContext frameworkBundleContext,
final String bundleURI,
final Integer desiredStartLevel) {
final Bundle bundle = frameworkBundleContext.installBundle(bundleURI);
if (desiredStartLevel != null) {
// Set the level at which the bundle should start.
// (Otherwise, it will start at the default level.)
final BundleStartLevel bundleStartLevel =
bundleAdapt(bundle, BundleStartLevel.class);
bundleStartLevel.setStartLevel(desiredStartLevel);
}
}
Now, all bundles are resolved and are either in the RESOLVED, ACTIVE or STARTED state.
Starting with osgi.clean=true
If I start the OSGi framework with option osgi.clean=true in the osgiConfig map and change the bundles installed from run to run that is nicely reflected in the framework.
If I e.g. start the framework with bundleX and bundleY and call
frameworkBundleContext.getBundles();
then I see exactly
The system bundle (ACTIVE)
bundleX (RESOLVED)
bundleY (RESOLVED)
If I shut down the program and retry this time with bundleX and bundleZ then I see (no surprise)
The system bundle (ACTIVE)
bundleX (RESOLVED)
bundleZ (RESOLVED)
Starting without osgi.clean
If I start the OSGi framework without setting osgi.clean in the osgiConfig map then installed bundles stick around from run to run and new bundles are not resolved.
So assume that I run one time with osgi.clean=true loading bundleX and bundleY and then shut down the program.
Now, when I and restart without osgi.clean and install only bundleZ, then I see:
The system bundle (ACTIVE)
bundleX (RESOLVED)
bundleY (RESOLVED)
bundleZ (INSTALLED) (i.e. not resolved yet)
So bundleX and bundleY survived from one run to another without having to be installed the 2nd time.
On the other hand, bundleZ does not resolve automatically. To get it to the RESOLVED state I need to do this:
final FrameworkWiring frameworkWiring = systemBundle.adapt(FrameworkWiring.class);
frameworkWiring.resolveBundles(null);
Question: Should I use osgi.clean or not?
It seems that using osgi.clean=true gives me a fresh start every time, whereas not using it means that bundle state survives from run to run. I guess the caching makes OSGi start faster but it does not seem to be a big deal for me (as I install the bundles using the "reference:" prefix which means the jars are not copied to the cache, only a reference to the original file location is kept).
However, my application is a multi process application running against the same OSGi configuration area. Is it a problem running with osgi.clean=true all the time in this situation?
Also, if somebody could point me to a good explanation of exactly what osgi.clean means and how caching in OSGi (Equinox) works I would appreciate it.

Answer 1

Ignore osgi.clean. Also please ignore start levels. The step you're missing is actually starting your bundles!
Each call to installBundle gives you a Bundle object. After installing all the bundles, you should then call start() on each of the returned bundle objects.
Any other way that you have been using to start bundles has been down to pure luck, i.e. because those bundles might once have been started and cached in that state. The same state would probably not be repeatable if you installed the application on another machine. So actually take control of your bundles and start them yourself.
You usually don't need to worry about the difference between INSTALLED and RESOLVED. Installed can simply mean "not resolved yet", e.g. because the bundle's exports weren't needed. If there are any resolving problems such as missing dependencies, then you will find out about them as BundleException when calling the start method.