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Re: [p2-dev] Processing of binary IUs

When we designed p2 we wanted to separate the download from the installation. There are several reasons for this:
- Be able to download everything in advance of the installation. This is necessary when you are trying to deploy the same app on a large number of machine and want to guarantee some sort of atomicity.
- Not modify the install until everything has been downloaded. In the case of eclipse many files are being downloaded which means that there are many chances for things to go wrong (dropped connection, corruption, etc.). If you start modifying the install while things are being downloaded, if things are going wrong then you will need to revert (which p2 can do), yet if you can avoid this it is always better.

For https://bugs.eclipse.org/bugs/show_bug.cgi?id=395127 you should be able to delete everything without a problem

On 14/06/2013 8:33 AM, Vladimir Prus wrote:


I have a couple of questions about dealing with binary IUs. For all I understand, first P2 downloads them to a local
directory (p2/org.eclipse.equinox.p2.core/cache) and then runs install instructions.

- Why is such local download necessary? Say, if install involves just unzipping, it should be possible to directly
stream data from a server and unpack them on the fly, without local storage of zipped data.

- I see there's a bug about binary cache having unbounded size - https://bugs.eclipse.org/bugs/show_bug.cgi?id=395127
How do people work this problem around? If I just wipe all this cache on product startup, will anything break?
I must admit I don't understand the purpose of caching here.