View source for Equinox/p2/Composite Repositories (new)

As repositories continually grow in size they become harder to manage. The goal of composite repositories is to make this task easier by allowing you to have a parent repository which refers to multiple children. Users are then able to reference the parent repository and the children's content will transparently be available to them. 

===How It Works===

With the built-in repository types defined by p2, when a user connects to a server we check to see if there are any files that we recognize. In particular for metadata repositories we look for a <code>content.xml</code> file or a <code>content.jar</code> and in the case of artifact repositories we look for an <code>artifacts.xml</code> or <code>artifacts.jar</code> file.

So in order to create a composite repository, all you need to do is create a new file (<code>compositeContent.xml/compositeContent.jar</code> or <code>compositeArtifacts.xml/compositeArtifacts.jar</code>) and p2 will recognize that you have defined a composite repository and load it from there.

===Sample Composite Metadata Repository===

In the sample files below there is a parent repository with two children. Note that the physical location of the children (in this example) are relative paths which are sub-folders of the parent. For instance, if the location of the parent is <code>http://example.eclipse.org/updates</code> then the children are <code>http://example.eclipse.org/updates/childOne</code> and <code>http://example.eclipse.org/updates/childTwo</code>. You are also able to use absolute URIs as the children repository locations.

File: <code>compositeContent.xml</code>

<pre>
<?xml version='1.0' encoding='UTF-8'?>
<?compositeMetadataRepository version='1.0.0'?>
<repository name='&amp;quot;Eclipse Project Test Site&amp;quot;'
    type='org.eclipse.equinox.internal.p2.metadata.repository.CompositeMetadataRepository' version='1.0.0'>
  <properties size='1'>
    <property name='p2.timestamp' value='1243822502499'/>
  </properties>
  <children size='2'>
    <child location='childOne'/>
    <child location='childTwo'/>
  </children>
</repository>
</pre>

===Sample Composite Artifact Repository===

File: <code>compositeArtifacts.xml</code>

<pre>
<?xml version='1.0' encoding='UTF-8'?>
<?compositeArtifactRepository version='1.0.0'?>
<repository name='&amp;quot;Eclipse Project Test Site&amp;quot;'
    type='org.eclipse.equinox.internal.p2.artifact.repository.CompositeArtifactRepository' version='1.0.0'>
  <properties size='1'>
    <property name='p2.timestamp' value='1243822502440'/>
  </properties>
  <children size='2'>
    <child location='childOne'/>
    <child location='childTwo'/>
  </children>
</repository>
</pre>

==Composite Repositories as part of the build==

In order to automate composite repository actions in release engineering builds, we have created Ant tasks which can be called to create and modify repositories. The tasks are defined in the <code>org.eclipse.equinox.p2.repository.tools</code> bundle.

===p2.composite.repository===

====Attributes====
* ''failOnExists'' - Whether we should fail if the repository already exists. (Default is ''false'') 
* ''validate'' -  A comparator-id. Child repositories claiming to contain the same artifact are compared using the given comparator. These are extensions to the org.eclipse.equinox.p2.artifact.repository.artifactComparators extension point. Comparators provided by p2 are: 
** <code>org.eclipse.equinox.p2.repository.tools.jar.comparator</code>: Compare jars. Class files are dissassembled and compared for equivalence, properties and manifest files are compared as such, all other files are compared byte-for-byte. 
** <code>org.eclipse.equinox.artifact.md5.comparator</code>: Compare the MD5 sums as recorded in the artifact repositories. 
 
====Sub-elements====
* ''add'' - A nested element containing a list of repositories to add to the composite. 
* ''remove'' - A nested element containing a list repositories to remove from the composite.

===Examples===
Some example Ant tasks for composite repositories and further explanation can be found on the [[Equinox/p2/Ant_Tasks#Composite_Repository_Task | p2 Ant tasks]] page.

[[Category: Equinox p2|Composite Repositories2]]