http 500, "case_clause / system limit, open_port"

Binary package hint: couchdb

it caused HTTP 500 and couchdb described it as
{"error":"case_clause","reason":"{system_limit,[{erlang,open_port,[{spawn,\"couch_erl_driver\"},[]]},\n {couch_util,drv_port,0},\n {couch_util,collate,3},\n {couch_view,less_same_type,2},\n {couch_view,less_list,2},\n {couch_btree,find_first_gteq,5},\n {couch_btree,modify_kpnode,6},\n {couch_btree,modify_node,4}]}"}
{couch_httpd_auth,get_user,2},
             {couch_httpd_oauth,set_user_ctx,2},
             {couch_httpd,authenticate_request,2},
             {couch_httpd,handle_request,5},
             {mochiweb_http,headers,5},
             {proc_lib,init_p_do_apply,3}