Cache generated names until disk files are written

src/machi_flu_filename_mgr.erl

@@ -43,12 +43,17 @@
 -module(machi_flu_filename_mgr).
 -behavior(gen_server).
 
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+-compile(export_all).
+-endif.
+
 -export([
     child_spec/2,
     start_link/2,
-    find_or_make_filename_from_prefix/1,
-    increment_prefix_sequence/1,
-    list_files_by_prefix/1
+    find_or_make_filename_from_prefix/2,
+    increment_prefix_sequence/2,
+    list_files_by_prefix/2
     ]).
 
 %% gen_server callbacks
@@ -63,6 +68,11 @@
 
 -define(TIMEOUT, 10 * 1000).
 
+-record(state, {fluname :: atom(),
+                tid     :: ets:tid(),
+                datadir :: file:dir()
+               }).
+
 %% public API
 
 child_spec(FluName, DataDir) ->
@@ -72,75 +82,63 @@ child_spec(FluName, DataDir) ->
         permanent, 5000, worker, [?MODULE]}.
 
 start_link(FluName, DataDir) when is_atom(FluName) andalso is_list(DataDir) ->
-    gen_server:start_link({local, make_filename_mgr_name(FluName)}, ?MODULE, [DataDir], []).
+    N = make_filename_mgr_name(FluName),
+    gen_server:start_link({local, N}, ?MODULE, [FluName, DataDir], []).
 
--spec find_or_make_filename_from_prefix( Prefix :: {prefix, string()} ) ->
+-spec find_or_make_filename_from_prefix( FluName :: atom(), Prefix :: {prefix, string()} ) ->
         {file, Filename :: string()} | {error, Reason :: term() } | timeout.
 % @doc Find the latest available or make a filename from a prefix. A prefix
 % should be in the form of a tagged tuple `{prefix, P}'. Returns a tagged
 % tuple in the form of `{file, F}' or an `{error, Reason}'
-find_or_make_filename_from_prefix({prefix, Prefix}) ->
-    gen_server:call(?MODULE, {find_filename, Prefix}, ?TIMEOUT); 
-find_or_make_filename_from_prefix(Other) ->
+find_or_make_filename_from_prefix(FluName, {prefix, Prefix}) when is_atom(FluName) ->
+    N = make_filename_mgr_name(FluName),
+    gen_server:call(N, {find_filename, Prefix}, ?TIMEOUT); 
+find_or_make_filename_from_prefix(_FluName, Other) ->
     lager:error("~p is not a valid prefix.", [Other]),
     error(badarg).
 
--spec increment_prefix_sequence( Prefix :: {prefix, string()} ) ->
+-spec increment_prefix_sequence( FluName :: atom(), Prefix :: {prefix, string()} ) ->
         ok | {error, Reason :: term() } | timeout.
 % @doc Increment the sequence counter for a given prefix. Prefix should
 % be in the form of `{prefix, P}'. 
-increment_prefix_sequence({prefix, Prefix}) ->
-    gen_server:call(?MODULE, {increment_sequence, Prefix}, ?TIMEOUT); 
-increment_prefix_sequence(Other) ->
+increment_prefix_sequence(FluName, {prefix, Prefix}) when is_atom(FluName) ->
+    gen_server:call(make_filename_mgr_name(FluName), {increment_sequence, Prefix}, ?TIMEOUT); 
+increment_prefix_sequence(_FluName, Other) ->
     lager:error("~p is not a valid prefix.", [Other]),
     error(badarg).
 
--spec list_files_by_prefix( Prefix :: {prefix, string()} ) ->
+-spec list_files_by_prefix( FluName :: atom(), Prefix :: {prefix, string()} ) ->
     [ file:name() ] | timeout | {error, Reason :: term() }.
 % @doc Given a prefix in the form of `{prefix, P}' return
 % all the data files associated with that prefix. Returns
 % a list.
-list_files_by_prefix({prefix, Prefix}) ->
-    gen_server:call(?MODULE, {list_files, Prefix}, ?TIMEOUT); 
-list_files_by_prefix(Other) ->
+list_files_by_prefix(FluName, {prefix, Prefix}) when is_atom(FluName) ->
+    gen_server:call(make_filename_mgr_name(FluName), {list_files, Prefix}, ?TIMEOUT); 
+list_files_by_prefix(_FluName, Other) ->
     lager:error("~p is not a valid prefix.", [Other]),
     error(badarg).
 
 %% gen_server API
-init([DataDir]) ->
-    {ok, DataDir}.
+init([FluName, DataDir]) ->
+    Tid = ets:new(make_filename_mgr_name(FluName), [named_table, {read_concurrency, true}]),
+    {ok, #state{ fluname = FluName, datadir = DataDir, tid = Tid }}.
 
 handle_cast(Req, State) ->
     lager:warning("Got unknown cast ~p", [Req]),
     {noreply, State}.
 
-handle_call({find_filename, Prefix}, _From, DataDir) ->
-    N = machi_util:read_max_filenum(DataDir, Prefix),
-    File = case find_file(DataDir, Prefix, N) of
-        [] ->
-            {F, _} = machi_util:make_data_filename(
-              DataDir,
-              Prefix,
-              generate_uuid_v4_str(),
-              N),
-             F;
-        [H] -> H;
-        [Fn | _ ] = L -> 
-            lager:warning(
-              "Searching for a matching file to prefix ~p and sequence number ~p gave multiples: ~p",
-              [Prefix, N, L]),
-            Fn
-    end,
-    {reply, {file, File}, DataDir};
-handle_call({increment_sequence, Prefix}, _From, DataDir) ->
+handle_call({find_filename, Prefix}, _From, S = #state{ datadir = DataDir, tid = Tid }) ->
+    File = handle_find_file(Tid, Prefix, DataDir),
+    {reply, {file, File}, S};
+handle_call({increment_sequence, Prefix}, _From, S = #state{ datadir = DataDir }) ->
     ok = machi_util:increment_max_filenum(DataDir, Prefix),
-    {reply, ok, DataDir};
-handle_call({list_files, Prefix}, From, DataDir) ->
+    {reply, ok, S};
+handle_call({list_files, Prefix}, From, S = #state{ datadir = DataDir }) ->
     spawn(fun() -> 
         L = list_files(DataDir, Prefix),
         gen_server:reply(From, L)
     end),
-    {noreply, DataDir};
+    {noreply, S};
 
 handle_call(Req, From, State) ->
     lager:warning("Got unknown call ~p from ~p", [Req, From]),
@@ -176,3 +174,47 @@ list_files(DataDir, Prefix) ->
 
 make_filename_mgr_name(FluName) when is_atom(FluName) ->
     list_to_atom(atom_to_list(FluName) ++ "_filename_mgr").
+
+handle_find_file(Tid, Prefix, DataDir) ->
+    N = machi_util:read_max_filenum(DataDir, Prefix),
+    {File, Cleanup} = case find_file(DataDir, Prefix, N) of
+        [] ->
+            {find_or_make_filename(Tid, DataDir, Prefix, N), false};
+        [H] -> {H, true};
+        [Fn | _ ] = L -> 
+            lager:warning(
+              "Searching for a matching file to prefix ~p and sequence number ~p gave multiples: ~p",
+              [Prefix, N, L]),
+            {Fn, true}
+    end,
+    maybe_cleanup(Tid, {Prefix, N}, Cleanup),
+    filename:basename(File).
+
+find_or_make_filename(Tid, DataDir, Prefix, N) ->
+    case ets:lookup(Tid, {Prefix, N}) of
+         [] ->
+            F = generate_filename(DataDir, Prefix, N),
+            true = ets:insert_new(Tid, {{Prefix, N}, F}),
+            F;
+        [{_Key, File}] ->
+            File
+    end.
+
+generate_filename(DataDir, Prefix, N) ->
+    {F, _} = machi_util:make_data_filename(
+              DataDir,
+              Prefix,
+              generate_uuid_v4_str(),
+              N),
+    binary_to_list(F).
+
+maybe_cleanup(_Tid, _Key, false) ->
+    ok;
+maybe_cleanup(Tid, Key, true) ->
+    ok = ets:delete(Tid, Key).
+
+
+-ifdef(TEST).
+
+-endif.
+