Cache connection info

src/gmhc_eureka.erl

@@ -2,19 +2,88 @@
 -vsn("0.6.1").
 
 -export([get_pool_address/0]).
+-export([cache_good_address/1,
+         invalidate_cache/0]).
 
 -include_lib("kernel/include/logger.hrl").
 -include("gmhc_events.hrl").
 
 get_pool_address() ->
+    case cached_address() of
+        {ok, _} = Ok -> Ok;
+        {error, _} ->
+            get_pool_address_()
+    end.
+
+cached_address() ->
+    CacheF = cache_filename(),
+    ?LOG_DEBUG("Eureka cache filename: ~p", [CacheF]),
+    case file:read_file(CacheF) of
+        {ok, Bin} ->
+            NowTS = erlang:system_time(seconds),
+            OldestTS = NowTS - 24*60*60,
+            try binary_to_term(Bin) of
+                #{ ts      := TS
+                 , host    := _
+                 , port    := _
+                 , pool_id := _} = Map ->
+                    if TS >= OldestTS ->
+                            Result = maps:remove(ts, Map),
+                            ?LOG_DEBUG("Cached eureka info: ~p", [Result]),
+                            {ok, Result};
+                       true ->
+                            {error, outdated}
+                    end;
+                Other ->
+                    {error, {invalid_cache_term, Other}}
+            catch
+                error:E ->
+                    {error, {invalid_cache_data, E}}
+            end;
+        {error, _} = Err ->
+            Err
+    end.
+
+cache_good_address(#{host := Addr,
+                     port := Port,
+                     pool_id := PoolId}) ->
+    CacheF = cache_filename(),
+    ToCache = #{ host => unicode:characters_to_binary(Addr)
+               , port => Port
+               , pool_id => unicode:characters_to_binary(PoolId)
+               , ts => erlang:system_time(seconds)},
+    case file:write_file(CacheF, term_to_binary(ToCache)) of
+        ok ->
+            ?LOG_DEBUG("Cached eureka info in: ~p", [CacheF]),
+            {ok, ToCache};
+        {error, _} = Err ->
+            ?LOG_DEBUG("Couldn't cache eureka in ~p: ~p", [CacheF, Err]),
+            Err
+    end.
+
+invalidate_cache() ->
+    CacheF = cache_filename(),
+    case file:delete_file(CacheF) of
+        ok ->
+            ?LOG_DEBUG("Eureka cache file removed (~p)", [CacheF]),
+            ok;
+        {error, _} = Err ->
+            ?LOG_DEBUG("Couldn't remove Eureka cache (~p): ~p", [CacheF, Err]),
+            Err
+    end.
+
+cache_filename() ->
+    filename:join(setup:data_dir(), "gmhc_eureka.cache").
+
+get_pool_address_() ->
     case gmconfig:find_config([<<"pool_admin">>, <<"url">>], [user_config]) of
         {ok, URL0} ->
             case expand_url(URL0) of
                 <<"local">> ->
-                    #{<<"address">> => <<"127.0.0.1">>,
-                      <<"port">>    => gmconfig:get_config(
-                                         [<<"pool">>, <<"port">>], [schema_default]),
-                      <<"pool_id">> => gmhc_config:get_config([<<"pool">>, <<"id">>]) };
+                    #{host    => <<"127.0.0.1">>,
+                      port    => gmconfig:get_config(
+                                   [<<"pool">>, <<"port">>], [schema_default]),
+                      pool_id => gmhc_config:get_config([<<"pool">>, <<"id">>]) };
                 URL ->
                     ?LOG_INFO("Trying to connect to ~p", [URL]),
                     connect1(URL)
@@ -49,9 +118,13 @@ connect1(URL0) ->
             Error
     end.
 
-get_host_port(Data) ->
+get_host_port(#{ <<"address">> := Addr
+               , <<"port">>    := Port
+               , <<"pool_id">> := PoolId } = Data) ->
     ?LOG_DEBUG("Data = ~p", [Data]),
-    maps:with([<<"address">>, <<"port">>, <<"pool_id">>], Data).
+    {ok, #{ host => Addr
+          , port => Port
+          , pool_id => PoolId }}.
 
 request(get, URL) ->
     case request(get, URL, []) of