Break out connection and session startup into functions.

src/riak_kv_wterl_backend.erl

@@ -24,8 +24,6 @@
 -behavior(temp_riak_kv_backend).
 -author('Steve Vinoski <steve@basho.com>').
 
--compile([{parse_transform, lager_transform}]).
-
 %% KV Backend API
 -export([api_version/0,
          capabilities/1,
@@ -53,8 +51,8 @@
 -define(CAPABILITIES, [async_fold]).
 
 -record(state, {table :: string(),
-                session :: wterl:session(),
+                connection :: wterl:connection(),
-                partition :: integer()}).
+                session :: wterl:session()}).
 
 -type state() :: #state{}.
 -type config() :: [{atom(), term()}].
@@ -82,54 +80,22 @@ capabilities(_, _) ->
 %% @doc Start the wterl backend
 -spec start(integer(), config()) -> {ok, state()} | {error, term()}.
 start(Partition, Config) ->
-    %% Get the data root directory
     Table = "lsm:wt" ++ integer_to_list(Partition),
-    case app_helper:get_prop_or_env(data_root, Config, wterl) of
+    AppStart =
-        undefined ->
+        case application:start(wterl) of
-            lager:error("Failed to create wterl dir: data_root is not set"),
+            ok ->
-            {error, data_root_unset};
+                ok;
-        DataRoot ->
+            {error, {already_started, _}} ->
-            Started =
+                ok;
-                case application:start(wterl) of
+        {error, Reason1} ->
-                    ok ->
+            lager:error("Failed to start wterl: ~p", [Reason1]),
-                        wterl_conn:is_open();
+            {error, Reason1}
-                    {error, {already_started, _}} ->
+        end,
-                        wterl_conn:is_open();
+    case AppStart of
-                    {error, Reason1} ->
+        ok ->
-                        lager:error("Failed to start wterl: ~p", [Reason1]),
+            establish_connection(Table, Config);
-                        {error, Reason1}
+        {error, Reason2} ->
-                end,
+            {error, Reason2}
-            case Started of
-                false ->
-                    ok = filelib:ensure_dir(filename:join(DataRoot, "x")),
-                    SessionMax =
-                        case app_helper:get_prop_or_env(ring_creation_size, Config, riak_core) of
-                            undefined -> 1024;
-                            RingSize when RingSize < 512 -> 1024;
-                            RingSize -> RingSize * 2
-                        end,
-                    case wterl_conn:open(DataRoot,
-                                         [Config,
-                                          {create, true},
-                                          {sync, false},
-                                          {logging, true},
-                                          {transactional, true},
-                                          {session_max, SessionMax},
-                                          {cache_size, size_cache(Config)},
-                                          {checkpoint, [{wait, 1}]}, % sec
-                                          {statistics_log, [{wait, 30}]} % sec
-                                         ]) of
-                        {ok, _Connection} ->
-                            {ok, #state{partition=Partition, table=Table}};
-                        {error, Reason2} ->
-                            lager:error("Failed to establish a WiredTiger connection, wterl backend unable to start: ~p\n", [Reason2]),
-                            {error, Reason2}
-                    end;
-                true ->
-                    {ok, #state{partition=Partition, table=Table}};
-                {error, Reason3} ->
-                    {error, Reason3}
-            end
     end.
 
 %% @doc Stop the wterl backend
@@ -145,7 +111,7 @@ stop(#state{session=Session}) ->
                  {ok, not_found, state()} |
                  {error, term(), state()}.
 get(Bucket, Key, #state{session=undefined}=State) ->
-    get(Bucket, Key, establish_connection(State));
+    get(Bucket, Key, establish_session(State));
 get(Bucket, Key, #state{session=Session, table=Table}=State) ->
     WTKey = to_object_key(Bucket, Key),
     case wterl:session_get(Session, Table, WTKey) of
@@ -166,7 +132,7 @@ get(Bucket, Key, #state{session=Session, table=Table}=State) ->
                  {ok, state()} |
                  {error, term(), state()}.
 put(Bucket, PrimaryKey, IndexSpecs, Val, #state{session=undefined}=State) ->
-    put(Bucket, PrimaryKey, IndexSpecs, Val, establish_connection(State));
+    put(Bucket, PrimaryKey, IndexSpecs, Val, establish_session(State));
 put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{session=Session, table=Table}=State) ->
     WTKey = to_object_key(Bucket, PrimaryKey),
     case wterl:session_put(Session, Table, WTKey, Val) of
@@ -184,7 +150,7 @@ put(Bucket, PrimaryKey, _IndexSpecs, Val, #state{session=Session, table=Table}=S
                     {ok, state()} |
                     {error, term(), state()}.
 delete(Bucket, Key, IndexSpecs, #state{session=undefined}=State) ->
-    delete(Bucket, Key, IndexSpecs, establish_connection(State));
+    delete(Bucket, Key, IndexSpecs, establish_session(State));
 delete(Bucket, Key, _IndexSpecs, #state{session=Session, table=Table}=State) ->
     WTKey = to_object_key(Bucket, Key),
     case wterl:session_delete(Session, Table, WTKey) of
@@ -313,7 +279,7 @@ fold_objects(FoldObjectsFun, Acc, Opts, #state{table=Table}) ->
 %% @doc Delete all objects from this wterl backend
 -spec drop(state()) -> {ok, state()} | {error, term(), state()}.
 drop(#state{session=undefined}=State) ->
-    drop(establish_connection(State));
+    drop(establish_session(State));
 drop(#state{table=Table, session=Session}=State) ->
     case wterl:session_truncate(Session, Table) of
         ok ->
@@ -326,7 +292,7 @@ drop(#state{table=Table, session=Session}=State) ->
 %% non-tombstone values; otherwise returns false.
 -spec is_empty(state()) -> boolean().
 is_empty(#state{session=undefined}=State) ->
-    is_empty(establish_connection(State));
+    is_empty(establish_session(State));
 is_empty(#state{table=Table, session=Session}) ->
     {ok, Cursor} = wterl:cursor_open(Session, Table),
     try
@@ -338,7 +304,7 @@ is_empty(#state{table=Table, session=Session}) ->
 %% @doc Get the status information for this wterl backend
 -spec status(state()) -> [{atom(), term()}].
 status(#state{session=undefined}=State) ->
-    status(establish_connection(State));
+    status(establish_session(State));
 status(#state{table=Table, session=Session}) ->
     {ok, Cursor} = wterl:cursor_open(Session, "statistics:"++Table),
     try
@@ -358,7 +324,40 @@ callback(_Ref, _Msg, State) ->
 %% Internal functions
 %% ===================================================================
 
-establish_connection(#state{table=Table, session=undefined}=State) ->
+establish_connection(Table, Config) ->
+    %% Get the data root directory
+    case app_helper:get_prop_or_env(data_root, Config, wterl) of
+        undefined ->
+            lager:error("Failed to create wterl dir: data_root is not set"),
+            {error, data_root_unset};
+        DataRoot ->
+            ok = filelib:ensure_dir(filename:join(DataRoot, "x")),
+            SessionMax =
+                case app_helper:get_prop_or_env(ring_creation_size, Config, riak_core) of
+                    undefined -> 1024;
+                    RingSize when RingSize < 512 -> 1024;
+                    RingSize -> RingSize * 2
+                end,
+            case wterl_conn:open(DataRoot,
+                                 [Config,
+                                  {create, true},
+                                  {sync, false},
+                                  {logging, true},
+                                  {transactional, true},
+                                  {session_max, SessionMax},
+                                  {cache_size, size_cache(Config)},
+                                  {checkpoint, [{wait, 1}]}, % sec
+                                  {statistics_log, [{wait, 30}]} % sec
+                                 ]) of
+                {ok, Connection} ->
+                    {ok, #state{table=Table, connection=Connection}};
+                {error, Reason2} ->
+                    lager:error("Failed to establish a WiredTiger connection, wterl backend unable to start: ~p\n", [Reason2]),
+                    {error, Reason2}
+            end
+    end.
+
+establish_session(#state{table=Table, session=undefined}=State) ->
     {ok, Connection} = wterl_conn:get(),
     case wterl:session_open(Connection, wterl:config_to_bin([{isolation, "snapshot"}])) of
         {ok, Session} ->
@@ -379,7 +378,7 @@ establish_connection(#state{table=Table, session=undefined}=State) ->
             lager:error("Failed to open a WiredTiger session: ~p\n", [Reason]),
             State
     end;
-establish_connection(State) ->
+establish_session(State) ->
     State.
 
 %% @private