Restructure the way we create/merge default configuration setttings

with user supplied settings.  Move cache estimate to its own function.

src/riak_kv_wiredtiger_backend.erl

@@ -2,7 +2,7 @@
 %%
 %% riak_kv_wiredtiger_backend: Use WiredTiger for Riak/KV storage
 %%
-%% Copyright (c) 2012-2013 Basho Technologies, Inc.  All Rights Reserved.
+%% Copyright (c) 2012 Basho Technologies, Inc.  All Rights Reserved.
 %%
 %% This file is provided to you under the Apache License,
 %% Version 2.0 (the "License"); you may not use this file
@@ -83,31 +83,11 @@ capabilities(_, _) ->
 start(Partition, Config0) ->
     %% Get the data root directory
     case app_helper:get_prop_or_env(data_root, Config0, wt) of
-	<<"">> ->
-            lager:error("Failed to startup WiredTiger: data_root is not valid"),
-            {error, data_root_unset};
-	[] ->
-            lager:error("Failed to startup WiredTiger: data_root is empty"),
-            {error, data_root_unset};
         undefined ->
             lager:error("Failed to startup WiredTiger: data_root is not set"),
             {error, data_root_unset};
         DataRoot ->
 	    Config = lists:keydelete(data_root, 1, Config0),
-	    CacheSize =
-		case proplists:get_value(cache_size, Config) of
-		    undefined ->
-			case application:get_env(wt, cache_size) of
-			    {ok, Value} ->
-				Value;
-			    _ ->
-				SizeEst = best_guess_at_a_reasonable_cache_size(64),
-				%% lager:warning("Using estimated best cache size of ~p for WiredTiger backend.", [SizeEst]),
-				SizeEst
-			end;
-		    Value ->
-			Value
-		end,
 	    AppStarted =
 		case application:start(wt) of
 		    ok ->
@@ -120,6 +100,7 @@ start(Partition, Config0) ->
 		end,
 	    case AppStarted of
 		ok ->
+		    CacheSize = size_cache(64, Config),
 		    ConnectionOpts =
 			[Config,
 			 {create, true},
@@ -475,6 +456,21 @@ fetch_status(Cursor, {ok, Stat}, Acc) ->
     [What,Val|_] = [binary_to_list(B) || B <- binary:split(Stat, [<<0>>], [global])],
     fetch_status(Cursor, wt:cursor_next_value(Cursor), [{What,Val}|Acc]).
 
+size_cache(ChunkSize, Config) ->
+    case proplists:get_value(cache_size, Config) of
+	undefined ->
+	    case application:get_env(wt, cache_size) of
+		{ok, Value} ->
+		    Value;
+		_ ->
+		    SizeEst = best_guess_at_a_reasonable_cache_size(ChunkSize),
+		    %% lager:warning("Using estimated best cache size of ~p for WiredTiger backend.", [SizeEst]),
+		    SizeEst
+	    end;
+	Value ->
+	    Value
+    end.
+
 best_guess_at_a_reasonable_cache_size(ChunkSizeInMB) ->
     RunningApps = application:which_applications(),
     case proplists:is_defined(sasl, RunningApps) andalso

src/temp_riak_kv_backend.erl

@@ -272,7 +272,7 @@ empty_check({Backend, State}) ->
     }.
 
 setup({BackendMod, Config}) ->
-    {ok, S} = BackendMod:start(0, Config),
+    {ok, S} = BackendMod:start(42, Config),
     {BackendMod, S}.
 
 cleanup({BackendMod, S}) ->

src/wt_conn.erl

@@ -2,7 +2,7 @@
 %%
 %% wt_conn: manage a connection to WiredTiger
 %%
-%% Copyright (c) 2012-2013 Basho Technologies, Inc. All Rights Reserved.
+%% Copyright (c) 2012 Basho Technologies, Inc. All Rights Reserved.
 %%
 %% This file is provided to you under the Apache License,
 %% Version 2.0 (the "License"); you may not use this file
@@ -26,6 +26,7 @@
 
 -ifdef(TEST).
 -include_lib("eunit/include/eunit.hrl").
+-compile(export_all).
 -endif.
 
 %% API
@@ -83,26 +84,7 @@ init([]) ->
     {ok, #state{}}.
 
 handle_call({open, Dir, Config, Caller}, _From, #state{conn=undefined}=State) ->
-    OptsA =
+    Opts = tailor_config(Config),
-	case proplists:get_bool(create, Config) of
-	    false -> [{create, false}];
-	    _ ->     [{create, true}]
-	end,
-    OptsB =
-	case proplists:is_defined(shared_cache, Config) of
-	    true ->
-		[];
-	    false ->
-		[config_value(cache_size, Config, "512MB")]
-	end,
-    OptsC =
-	case proplists:is_defined(session_max, Config) of
-	    true ->
-		[];
-	    false ->
-		[config_value(session_max, Config, 100)]
-	end,
-    Opts = lists:merge([OptsA, OptsB, OptsC, Config]),
     {Reply, NState} =
 	case wt:conn_open(Dir, wt:config_to_bin(Opts)) of
 	    {ok, ConnRef}=OK ->
@@ -192,6 +174,35 @@ do_close(ConnRef) ->
 config_value(Key, Config, Default) ->
     {Key, app_helper:get_prop_or_env(Key, Config, wt, Default)}.
 
+%% @private
+map_cfg([], Acc) ->
+    Acc;
+map_cfg([Fun|T], Acc) ->
+    map_cfg(T, Fun(Acc)).
+
+tailor_config(Config) ->
+    map_cfg([fun (Acc) ->
+		     case proplists:is_defined(create, Acc) of
+			 false -> [{create, true} | Acc];
+			 true -> Acc
+		     end
+		 end,
+	     fun (Acc) ->
+		     case proplists:is_defined(shared_cache, Acc) of
+			 false ->
+			     [config_value(cache_size, Acc, "512MB") | Acc];
+			 true ->
+			     Acc
+		     end
+	     end,
+	     fun (Acc) ->
+		     case proplists:is_defined(session_max, Acc) of
+			 false ->
+			     [config_value(session_max, Acc, 100) | Acc];
+			 true ->
+			     Acc
+		     end
+	     end], Config).
 
 -ifdef(TEST).