WIP: projection store: read, get latest epoch

src/machi_flu1.erl

@@ -550,24 +550,26 @@ do_projection_command(Sock, LenHex, S) ->
         {ok, ProjCmdBin} = gen_tcp:recv(Sock, Len),
         ok = inet:setopts(Sock, [{packet, line}]),
         ProjCmd = binary_to_term(ProjCmdBin),
-        case handle_projection_command(ProjCmd, S) of
+        put(hack, ProjCmd),
-            ok ->
+        Res = handle_projection_command(ProjCmd, S),
-                ok = gen_tcp:send(Sock, <<"OK\n">>);
+        ResBin = term_to_binary(Res),
-            {error, written} ->
+        ResLenHex = machi_util:int_to_hexbin(byte_size(ResBin), 32),
-                ok = gen_tcp:send(Sock, <<"ERROR WRITTEN\n">>);
+        ok = gen_tcp:send(Sock, [<<"OK ">>, ResLenHex, <<"\n">>, ResBin])
-            {error, not_written} ->
-                ok = gen_tcp:send(Sock, <<"ERROR NOT-WRITTEN\n">>);
-            Else ->
-                TODO = list_to_binary(io_lib:format("TODO-YOLO-~w", [Else])),
-                ok = gen_tcp:send(Sock, [<<"ERROR ">>, TODO, <<"\n">>])
-        end
     catch
         What:Why ->
+            io:format(user, "OOPS ~p\n", [get(hack)]),
+            io:format(user, "OOPS ~p ~p ~p\n", [What, Why, erlang:get_stacktrace()]),
             WHA = list_to_binary(io_lib:format("TODO-YOLO.~w:~w-~w",
                                                [What, Why, erlang:get_stacktrace()])),
             _ = (catch gen_tcp:send(Sock, [<<"ERROR ">>, WHA, <<"\n">>]))
     end.
 
+handle_projection_command({get_latest_epoch, ProjType},
+                          #state{proj_store=ProjStore}) ->
+    machi_projection_store:get_latest_epoch(ProjStore, ProjType);
+handle_projection_command({read_projection, ProjType, Epoch},
+                          #state{proj_store=ProjStore}) ->
+    machi_projection_store:read(ProjStore, ProjType, Epoch);
 handle_projection_command({write_projection, ProjType, Proj},
                           #state{proj_store=ProjStore}) ->
     machi_projection_store:write(ProjStore, ProjType, Proj);

src/machi_flu1_client.erl

@@ -31,6 +31,8 @@
          list_files/2, list_files/3,
 
          %% Projection API
+         get_latest_epoch/2, get_latest_epoch/3,
+         read_projection/3, read_projection/4,
          write_projection/3, write_projection/4,
 
          %% Common API
@@ -146,6 +148,50 @@ list_files(Host, TcpPort, EpochID) when is_integer(TcpPort) ->
         catch gen_tcp:close(Sock)
     end.
 
+%% @doc Get the latest epoch number from the FLU's projection store.
+
+-spec get_latest_epoch(port(), projection_type()) ->
+      {ok, -1|non_neg_integer()} | {error, term()}.
+get_latest_epoch(Sock, ProjType)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    get_latest_epoch2(Sock, ProjType).
+
+%% @doc Get the latest epoch number from the FLU's projection store.
+
+-spec get_latest_epoch(inet_host(), inet_port(),
+                       projection_type()) ->
+      {ok, -1|non_neg_integer()} | {error, term()}.
+get_latest_epoch(Host, TcpPort, ProjType)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    Sock = machi_util:connect(Host, TcpPort),
+    try
+        get_latest_epoch2(Sock, ProjType)
+    after
+        catch gen_tcp:close(Sock)
+    end.
+
+%% @doc Read a projection `Proj' of type `ProjType'.
+
+-spec read_projection(port(), projection_type(), epoch_num()) ->
+      'ok' | {error, written} | {error, term()}.
+read_projection(Sock, ProjType, Epoch)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    read_projection2(Sock, ProjType, Epoch).
+
+%% @doc Read a projection `Proj' of type `ProjType'.
+
+-spec read_projection(inet_host(), inet_port(),
+                       projection_type(), epoch_num()) ->
+      'ok' | {error, written} | {error, term()}.
+read_projection(Host, TcpPort, ProjType, Epoch)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    Sock = machi_util:connect(Host, TcpPort),
+    try
+        read_projection2(Sock, ProjType, Epoch)
+    after
+        catch gen_tcp:close(Sock)
+    end.
+
 %% @doc Write a projection `Proj' of type `ProjType'.
 
 -spec write_projection(port(), projection_type(), projection()) ->
@@ -480,6 +526,14 @@ trunc_hack2(Sock, EpochID, File) ->
             {error, {badmatch, BadMatch}}
     end.
 
+get_latest_epoch2(Sock, ProjType) ->
+    ProjCmd = {get_latest_epoch, ProjType},
+    do_projection_common(Sock, ProjCmd).
+
+read_projection2(Sock, ProjType, Epoch) ->
+    ProjCmd = {read_projection, ProjType, Epoch},
+    do_projection_common(Sock, ProjCmd).
+
 write_projection2(Sock, ProjType, Proj) ->
     ProjCmd = {write_projection, ProjType, Proj},
     do_projection_common(Sock, ProjCmd).
@@ -492,13 +546,15 @@ do_projection_common(Sock, ProjCmd) ->
         LenHex = machi_util:int_to_hexbin(Len, 32),
         Cmd = [<<"PROJ ">>, LenHex, <<"\n">>],
         ok = gen_tcp:send(Sock, [Cmd, ProjCmdBin]),
+        ok = inet:setopts(Sock, [{packet, line}]),
         {ok, Line} = gen_tcp:recv(Sock, 0),
-        PathLen = byte_size(Line) - 3 - 16 - 1 - 1,
         case Line of
-            <<"OK\n">> ->
+            <<"OK ", ResLenHex:8/binary, "\n">> ->
-                ok;
+                ResLen = machi_util:hexstr_to_int(ResLenHex),
-            <<"ERROR WRITTEN\n">> ->
+                ok = inet:setopts(Sock, [{packet, raw}]),
-                {error, written};
+                {ok, ResBin} = gen_tcp:recv(Sock, ResLen),
+                ok = inet:setopts(Sock, [{packet, line}]),
+                binary_to_term(ResBin);
             Else ->
                 {error, Else}
         end

src/machi_projection_store.erl

@@ -25,6 +25,8 @@
 %% API
 -export([
          start_link/3,
+         get_latest_epoch/2, get_latest_epoch/3,
+         read/3, read/4,
          write/3, write/4
         ]).
 
@@ -37,14 +39,28 @@
           private_dir = ""       :: string(),
           wedged = true          :: boolean(),
           wedge_notify_pid       :: pid() | atom(),
-          max_public_epoch = -1  :: non_neg_integer(),
+          max_public_epoch = -1  :: -1 | non_neg_integer(),
-          max_private_epoch = -1 :: non_neg_integer()
+          max_private_epoch = -1 :: -1 | non_neg_integer()
          }).
 
 start_link(RegName, DataDir, NotifyWedgeStateChanges) ->
     gen_server:start_link({local, RegName},
                           ?MODULE, [DataDir, NotifyWedgeStateChanges], []).
 
+get_latest_epoch(PidSpec, ProjType) ->
+    get_latest_epoch(PidSpec, ProjType, infinity).
+
+get_latest_epoch(PidSpec, ProjType, Timeout)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    g_call(PidSpec, {get_latest_epoch, ProjType}, Timeout).
+
+read(PidSpec, ProjType, Epoch) ->
+    read(PidSpec, ProjType, Epoch, infinity).
+
+read(PidSpec, ProjType, Epoch, Timeout)
+  when ProjType == 'public' orelse ProjType == 'private' ->
+    g_call(PidSpec, {read, ProjType, Epoch}, Timeout).
+
 write(PidSpec, ProjType, Proj) ->
     write(PidSpec, ProjType, Proj, infinity).
 
@@ -79,6 +95,16 @@ g_call(PidSpec, Arg, Timeout) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+handle_call({{get_latest_epoch, ProjType}, LC1}, _From, S) ->
+    LC2 = lclock_update(LC1),
+    Epoch = if ProjType == public  -> S#state.max_public_epoch;
+               ProjType == private -> S#state.max_private_epoch
+            end,
+    {reply, {{ok, Epoch}, LC2}, S};
+handle_call({{read, ProjType, Epoch}, LC1}, _From, S) ->
+    LC2 = lclock_update(LC1),
+    {Reply, NewS} = do_proj_read(ProjType, Epoch, S),
+    {reply, {Reply, LC2}, NewS};
 handle_call({{write, ProjType, Proj}, LC1}, _From, S) ->
     LC2 = lclock_update(LC1),
     {Reply, NewS} = do_proj_write(ProjType, Proj, S),
@@ -101,6 +127,19 @@ code_change(_OldVsn, S, _Extra) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+do_proj_read(ProjType, Epoch, S) ->
+    Dir = pick_path(ProjType, S),
+    Path = filename:join(Dir, epoch2name(Epoch)),
+    case file:read_file(Path) of
+        {ok, Bin} ->
+            %% TODO and if Bin is corrupt? (even if binary_to_term() succeeds)
+            {{ok, binary_to_term(Bin)}, S};
+        {error, enoent} ->
+            {{error, not_written}, S};
+        {error, Else} ->
+            {{error, Else}, S}
+    end.
+
 do_proj_write(ProjType, #projection_v1{epoch_number=Epoch}=Proj, S) ->
     %% TODO: We probably ought to check the projection checksum for sanity, eh?
     Dir = pick_path(ProjType, S),

test/machi_flu1_test.erl

@@ -124,11 +124,19 @@ flu_projection_smoke_test() ->
 
     FLU1 = setup_test_flu(projection_test_flu, TcpPort, DataDir),
     try
+        {ok, -1} = ?FLU_C:get_latest_epoch(Host, TcpPort, public),
+        {ok, -1} = ?FLU_C:get_latest_epoch(Host, TcpPort, private),
+
         P1 = machi_projection:new(1, a, [a], [], [a], [], []),
         ok = ?FLU_C:write_projection(Host, TcpPort, public, P1),
         {error, written} = ?FLU_C:write_projection(Host, TcpPort, public, P1),
+        {ok, P1} = ?FLU_C:read_projection(Host, TcpPort, public, 1),
+        {error, not_written} = ?FLU_C:read_projection(Host, TcpPort, public, 2),
+
         ok = ?FLU_C:write_projection(Host, TcpPort, private, P1),
         {error, written} = ?FLU_C:write_projection(Host, TcpPort, private, P1),
+        {ok, P1} = ?FLU_C:read_projection(Host, TcpPort, private, 1),
+        {error, not_written} = ?FLU_C:read_projection(Host, TcpPort, private, 2),
 
         ok = ?FLU_C:quit(machi_util:connect(Host, TcpPort))
     after