I looked through the code, and noticed:

A bit of code from [1]:

	handle_external_req(#httpd{
29	                        path_parts=[_DbName, _External, UrlName | _Path]
30	                    }=HttpReq, Db) ->
31	    process_external_req(HttpReq, Db, UrlName);
32	handle_external_req(#httpd{path_parts=[_, _]}=Req, _Db) ->
33	    send_error(Req, 404, <<"external_server_error">>, <<"No server
name specified.">>);
34	handle_external_req(Req, _) ->
35	    send_error(Req, 404, <<"external_server_error">>, <<"Broken
assumption">>).

>From what I have seen of erlang, this means if no DBName exists, then
it will not work. Maybe we could add a optional path without a dbname
so people could make global external handlers or would more code be
required?

[1] http://svn.apache.org/viewvc/couchdb/trunk/src/couchdb/couch_httpd_external.erl?view=markup