Hi,
We ran into a problem if galaxy is running behind multiple reverse proxies. Galaxy assumes that the X-Forwarded-Host header only contains a single host to which it redirects, but apache will append comma-separated components to it if it already exists, which is the case of multiple reverse proxies. The result is that galaxy sometimes (i.e. sometimes after user login, depending on browser specifics, and when installing toolshed tools) tries to redirect the browser to "hostname, hostname". Apache docs http://httpd.apache.org/docs/2.4/mod/mod_proxy.html#x-headers
I have a patch for galaxy in this pull request https://bitbucket.org/galaxy/galaxy-central/pull-request/560/use-first-component-of-x-forwarded-for/diff. That change fixes a file that makes the same assumption. The actual fix requires a change in Routes. The Routes PR is here https://github.com/bbangert/routes/pull/33, so actually fixing this requires an update of Routes after that pr is merged there.
Jan