Equinox/p2/p2.mirrorsURL

Disclaimer: this page is not authored by a p2 expert, I merely reproduced some information which I found difficult to collect -- Stephan

Enabling your repository to leverage mirrors

The p2.mirrorsURL should be added to your metadata so that p2 will see the list of available mirrors to choose during installation.

Where to add?

Adding this property to artifacts.xml is sufficient, since p2 uses a list of mirrors while retrieving artifacts, not the metadata itself. Obviously, artifacts.jar must be updated or replaced after changing artifact.xml.

Should composite repos be treated, too, or just their children (leaves)?

Just the leaves. No need to to specify the property in compositeArtifacts.xml/jar.

What to add?

The property has the following structure:

  <property name="p2.mirrorsURL" 
          value="http://www.eclipse.org/downloads/download.php?file={repository_path}&amp;format=xml&amp;protocol=http"/>

• replace {repository_path} with the path where your artifacts.jar sits on download.eclipse.org,
  e.g., for http://download.eclipse.org/eclipse/updates/3.6/R-3.6.2-201102101200/artifacts.jar the path would be /eclipse/updates/3.6/R-3.6.2-201102101200
• yes, & is 5 characters
• the last part, &protocol=http is important, since it restricts the list of mirrors to those that support http. Monitor bug 349679 for status/progress on p2 working with ftp sites. (In general, such as for zip files linked on download pages, and similar, the 'protocol' parameter is optional for the download.php script and when omitted both http and ftp mirrors are returned).

This p2.mirrorsURL property will tell p2 to use the given URL to fetch a list of available mirrors (in xml format).

How to add?

If you use a site.xml the word goes that this is where you should specify this property. The Equinox/p2/Publisher should automatically transfer this information into your metadata.

If you don't use a site.xml you may consider manually editing artifacts.xml (which of course can be automated using, e.g., an xsl template, like this p2.xsl from the Mylyn project). When manually editing artifacts.xml add the property to the existing list of properties right at the top of the document. Don't forget to update the size attribute of the enclosing <properties> element.

How to test?

First, you may paste the full URL you specified as the value into your browser (now collapse & to &). The result should be an XML file with lots of mirror URLs. Pasting one of these URLs into the browser should in turn take you to the directory holding your artifacts.jar and friends.

Secondly, to test whether install successfully uses mirrors you may use the following options file (stored, e.g., as /tmp/p2options):

 org.eclipse.equinox.p2.core/debug=true
 org.eclipse.equinox.p2.core/artifacts/mirrors=true

(The first line generally enables debugging p2, the second line selects specific tracing for mirror selection)

Then you may want to unpack a fresh Eclipse package and change into the eclipse directory.

Finally, use the Equinox/p2/Director application for installing your feature using this command line:

 ./eclipse -consoleLog -noSplash -debug /tmp/p2options -application org.eclipse.equinox.p2.director \
       -repository http://download.eclipse.org/myproject/myrepo \
       -installIU org.eclipse.myproject.myfeature.group

This should install your feature and print to the console where each artifact was downloaded from. If p2.mirrorsURL is not properly configured no such messages will be shown.

Conversely, you can disable the automatic mirror selection mechanism by setting the VM argument eclipse.p2.mirrors to false (remember that vm args have to be last on the command line preceded by the switch -vmargs).

Moving a repo to archive.eclipse.org

Another situation where redirected downloads are desirable is when a repo is moved from download.eclipse.org to archive.eclipse.org. For files references using the Find a Mirror script (http://www.eclipse.org/downloads/download.php?file=/path/to/a/file.zip) moving to archive is transparently handled by that script. This section is exploring how the same effect can be achieved for p2 repositories.

The obvious way might be through the use of p2.mirrorsURL, however, I couldn't get this to work -- Stephan.

The following strategy seems to do the job (although admittedly, not a candidate for beauty contests):

• when moving everything to archive.eclipse.org keep a copy of all metadata (artifacts.jar and all those) on download.eclipse.org.
• extract the .xml files and edit like so:

  for composite repositories

  edit both compositeContent.xml and compositeArtifacts.xml:

  • simply change all relative paths to absolute paths pointing to http://archive.eclipse.org/something

  for leaf repositories

  edit artifacts.xml (this is the ugly, unofficial approach - use at your own risk):

  • remove any p2.mirrorsURL property (and decrease the size of the enclosing <properties> element accordingly).
  • in the <mappings> element replace all occurrences of ${repoUrl} with the archive path to your repo, like http://archive.eclipse.org/objectteams/updates/ot0.7
  • to be on the safe side increment the p2.timestamp value in the top list of properties

After editing put the .xml files back into their respective jar.