Update git documentation with HAProxy details

Update the documentation for our public git servers to reflect that it's now a
pool of servers load balanced with HAProxy.

Change-Id: Ib8bfec5cf8b339f2dfb57aaaf46d988ff32fc261

doc/source/git.rst

@@ -12,6 +12,7 @@ At a Glance
 
 :Hosts:
   * https://git.openstack.org
+  * git*.openstack.org
 :Puppet:
   * :file:`modules/cgit`
   * :file:`modules/openstack_project/manifests/git.pp`
@@ -26,14 +27,20 @@ At a Glance
 Overview
 ========
 
-The OpenStack git repositories are hosted on this server and served up via
-https using cgit and via git:// by git-daemon.
+The OpenStack git repositories are hosted on a pool of CentOS servers with the
+EPEL repository that includes the cgit package. They are served up via https
+using cgit and via git:// by git-daemon behind HAProxy which handles load
+balancing across the nodes.
 
-Apache is running on a CentOS 6 system with the EPEL repository that includes
-the cgit package. SELinux is enabled and requires restorecon to be run against
-/var/lib/git to set the appropriate SELinux security context, this is handled
-by puppet.
+SELinux is enabled on these nodes and requires restorecon to be run against
+/var/lib/git to set the appropriate SELinux security context. SELinux rules are
+also in place to allow for Apache to run on a non-standard port so it can sit
+behind HAProxy. This is all handled by puppet.
+
+In order to mitigate potential problems with HTTP(S) responses, HAProxy is
+configured using the source balance method so that every request from a single
+host will be served by one backend node unless nodes are added or removed.
 
 The jeepyb script create-cgitrepos runs against projects.yaml to generate the
 /etc/cgitrepos file listing all the git repositories. The git repositories are
-synced from the Gerrit server.
+synced to all the nodes from the Gerrit server.