Make peer handling more efficient

Each service process maintains a dictionary of peers, mapping an
application alias to a {pid(), #diameter_caps{}} list of connected
peers. These lists are potentially large, peers were appended to the end
of the list for no particular reason, and these long lists were
constructed/deconstructed when filtering them for pick_peer callbacks.
Many simultaneous outgoing request could then slow the VM to a crawl,
with many scheduled processes mired in list manipulation.

The pseudo-dicts are now replaced by plain ets tables. The reason for
them was (once upon a time) to have an interface interchangeable with a
plain dict for debugging purposes, but strict swapablity hasn't been the
case for some time now, and in practice a swap has never taken place.

Additional tables mapping Origin-Host/Realm have also been introduced,
to minimize the size of the peers lists when peers are filtered on
host/realm. For example, a filter like

  {any, [{all, [realm, host]}, realm]}

is probably a very common case: preferring a Destination-Realm/Host
match before falling back on Destination-Realm alone. This is now more
efficiently (but not equivalently) expressed as

  {first, [{all, [realm, host]}, realm]}

to stop the search when the best match is made, and extracts peers from
host/realm tables instead of searching through the list of all peers
supporting the application in question. The code to try and start with a
lookup isn't exhaustive, and the 'any' filter is still as inefficient as
previously.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/diameter/test/diameter_traffic_SUITE.erl b/lib/diameter/test/diameter_traffic_SUITE.erl
index fe6dd7b617..76e939f272 100644
--- a/lib/diameter/test/diameter_traffic_SUITE.erl
+++ b/lib/diameter/test/diameter_traffic_SUITE.erl
@@ -724,7 +724,8 @@ send_any_2(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
                   {'Destination-Host', [?HOST(SN, "unknown.org")]}],
     ?answer_message(?UNABLE_TO_DELIVER)
-        = call(Config, Req, [{filter, {any, [host, realm]}}]).
+        = call(Config, Req, [{filter, {first, [{all, [host, realm]},
+                                               realm]}}]).
 
 %% Send with a conjunctive filter.
 send_all_1(Config) ->