People report a bug that when they refresh Maven repository in their web browser (repository.jboss.org), they get different results (missing artifacts). This appears like a big bug, however I would like to shed light into this rather cosmetic problem.
It is caused by our new infrastructure behind repository.jboss.org. Originally there was just one server that handled artifacts. As the load increased this solution started not to be good enough. Therefore we added two proxy machines in front of the original one. They serve as mirrors for the original instance and they are load balanced by Apache. A classical mirror is a complete copy of all artifacts. The proxy machines are not classical mirrors though. The files are served using proxy repositories of Sonatype Nexus, that stores just content people ask for on the machines. When an artifact is requested, Nexus delivers it from the local content and if he does not find it locally it tries to obtain it from the master. However directory listing in the web browser is always served from the locally stored content.
And this is the reason, why the two machines have different directory listing. If one artifact is requested by someone the load balancer uses one of the mirrors and the artifact is added to the directory listing of that particular instance. But when one display the repository listing and then refreshes it, what may happen is that the listing will be displayed from the second instance, that does not have the artifact yet .
So i you worry about your builds - no worry! Both mirrors are identical and always return all the requested artifacts (even if it appears they are not there). Browsing the repositories using web browser may be confusing though. I will fix the issue somehow buthe builds are fine so the problem is not that big as it appears to be.