Equinox p2 Shared Install
- 1 Summary of Needs
- 2 Proposed Solutions Discussed
- 3 Current Approach
- 4 Case study: How to create a shared install for 3 os/arch/ws combinations using a bundle pool
Summary of Needs
For certain installations of Eclipse, there will exist the notion of a shared installation -- this may be in the case of a Linux system where a base set of software is installed via packages (perhaps RPMs), or may be in a Maya deployment where shared profiles are defined in a central server. In both cases, it is necessary to perform reconciliation between the shared profile and the user's current instantiation of the profile including any modifications they may have made.
Beyond performing reconciliation, when a reconciliation can not be made, the user will need to be presented with the list of software that is no longer compatible after reconciliation similar to what happens when you upgrade to a new major version of FireFox. When the user is presented with the list of software that is no longer compatible, the option could then be presented to automatically search for newer versions of that software.
Proposed Solutions Discussed
Custom Configurator with Intelligence
One option would be to provide a custom configurator that replaces the standard one used in the provisioning work. This configurator could be structured to check the shared profile source and then compare against the current list of bundles. Since the configurator deals at the bundle level, and the reconciliation needs to happen at the IU-level, this would require a lot of mapping and complex logic.
Reconciler on Launch
Another option is to have a simple configurator start the runtime with only enough plugins to run the reconcilation logic. This would work with IUs and see if reconciliation is needed between the shared profile and the user's instantiation of this profile. The benefit of this solution is that the reconciler can leverage the provisioning agent, but there is the potential for impact to the Eclipse startup time (needs investigation to understand impact).
Simple Configurator with optional Reconciler
A third option is to have a simple configurator that knows about a shared bundle list and the user's bundle list. This configurator could then check if the shared bundle list has changed, and if it has, only use the shared list. The reconciler could then be launched on startup to allow updating the user's addons to the profile. This approach would partially work but not necessarily handle some cases such as those required by Maya where checking if the shared profile has changed is more complex.
For a first implementation, we have decided to attempt the Reconciler on Launch approach. Our thought is to have an Activator start that performs the reconciliation running on a bare-bones OSGi runtime. The reconciler would check for differences and update the user's profile as needed. Finally it would either continue to load the extra bundles into the current runtime or if some base software has changed, potentially reload the base OSGi runtime and then launch the desired application.
To begin, we are creating two bundles:
- org.eclipse.equinox.prov.shared - contains the activator and code to look up the shared profile
- org.eclipse.equinox.prov.reconciler - contains the reconciler to resolve the differences between two profiles
In addition, the shared bundle will have an extension point allowing an ISharedProfileProvider to be specified. In the case of Maya this would have an implementation that coordinates with the central server while the shared linux install would have a version that retrieves the shared profile that might have been installed via a packaging mechanism.
To enable the reconciliation to take place, there may be additional properties stored in config.ini or alternate configuration file that are used by the activator, profile provider, and reconciler.
The content in previous chapters seems to be dealing with having two profiles to synchronize. Another definition of a shared install, at least for me, is the want of sharing all common content of multiple eclipse installations.
So, in this case study I'd like to create an installation structure that throws all common content into a common bundle pool, well, I'd prefer the term artifact pool. Here is the structure I'd like to create:
* root dir * install location for windows * install location for solaris * install location for linux * common location
, with the common location containing all common things, like artifacts and readmes and such, and the install locations containing merely the OS-specific parts, and a profile each to maintain the installation (and the pool).
Prerequisites: a repository containing an eclipse product for all OS's
In order to create the installation structure above I'm going to create a repository containing IUs and artifacts for all the OS's I want. Since Eclipse 3.5 such a repository can be created as a byproduct of a standard pde build. How to set up pdebuild for such a product is beyond the scope of this article, but these properties are worth mentioning, setting them in your build(.properties) will generate a p2 repo as well as some zips containing the build result:
* p2.gathering=true * p2.metadata.repo=file:<repo location> * p2.artifact.repo=file:<repo location> * p2.flavor=tooling
My pdebuild is then launched with this command:
<java> -jar plugins/org.eclipse.equinox.launcher_<version>.jar -buildfile plugins/org.eclipse.pde.build_<version>/scripts/productBuild/productBuild.xml -application org.eclipse.ant.core.antRunner -DjavacDebugInfo=on -DjavacVerbose=false -DjavacFailOnError=true -Dbuilder=<build properties file> -Dconfigs="win32,win32,x86 linux,gtk,x86 linux,gtk,x86_64 solaris,gtk,sparc" -DbuildId=ignore
Once the build finished successfully by product will be ready for the OS combinations seen in the configs property above.
Installing with the bundlepool option
Using the director now I can install from the generated repository. The way I do it is by using Eclipse PDE, creation a new Eclipse Application launch config, with the application org.eclipse.equinox.p2.director.
Specifying -help as commandline option will respond with the list of available commands, in the end I install with the following set of options:
* -repository <location of my generated repo> * -installIU <IU name> ( hint: use -list to find out what IUs were available for install ) * -destination C:/WindRiver/destination_linux (this is my install location with things like the launcher exes) * -bundlePool C:/WindRiver/bundlePool (this is my pool with all the bundles, usable by every install) * -profile TestProfileLinux (I do generate one profile per installation) * -p2.os linux (This install is for linux) * -p2.ws gtk (This install is for gnome) * -p2.arch x86 (This install is for 32bit intel)
This director call will already give me an install structure like the desired one:
* root dir (C:/WindRiver) * install location for linux (C:/WindRiver/destination_linux) * common location (C:/WindRiver/bundlePool)
Now, repeating the director call with some argument changes will also give me solaris and windows installations, these changes
* -destination C:/WindRiver/destination_win32 * -profile TestProfileWin32 * -p2.os win32 * -p2.ws win32 * -p2.arch x86
for example will create a windows installation for my product, with the bundles being put into the pool.
Limitations when running the installation
Trying to launch the application from C:/WindRiver/destination_win32 proves the installation to be sane, every bundle is resolved successfully and the product is launched successfully. p2 is great :)
However, there are severe limitations yet to be overcome. Zipping up this installation and putting it into some completely different directory is not going to work. This roaming is not possible with bundle pools. The reason is absolute paths in some areas, preventing you from moving around the installation.
One such absolute path can be found in the launcher.ini file for your product. The file contains the option
* -install C:/WindRiver/destination_win32
however, I was able to move my application and then launch it fine by changing this absolute path to a relative one: -install ../destination_win32. After some tests I found out that "../destination_win32" will only work in cases where the PWD is the install directory, launching the product from anywhere else renders this path invalid. That's weird though, the .ini contains other relative paths, like the one for the launcher jar, so I guess those work fine.
Another location with an absolute path is the profile itself, it contains a reference to the bundle pool and will be broken if you move anything. So this will rule out any updates to the bundle pool I guess.
As a result of this case study I think I'd take away the fact that in principle everything is working fine, p2 is doing a great job there. Still, the lack of a roaming option for such installs is a bummer, it prevents me from using this great concept internally!