DAG for upgrade steps.

4 files changed, 209 insertions, 15 deletions

diff --git a/src/rabbit.erl b/src/rabbit.erl
index 8c36a9f0a4..206cb4211d 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -40,6 +40,8 @@
 
 -export([log_location/1]).
 
+-export([all_module_attributes/1]).
+
 %%---------------------------------------------------------------------------
 %% Boot steps.
 -export([maybe_insert_default_data/0]).
@@ -313,20 +315,21 @@ module_attributes(Module) ->
             V
     end.
 
-boot_steps() ->
+all_module_attributes(Name) ->
     AllApps = [App || {App, _, _} <- application:loaded_applications()],
     Modules = lists:usort(
                 lists:append([Modules
                               || {ok, Modules} <-
                                      [application:get_key(App, modules)
                                       || App <- AllApps]])),
-    UnsortedSteps =
-        lists:flatmap(fun (Module) ->
-                              [{StepName, Attributes}
-                               || {rabbit_boot_step, [{StepName, Attributes}]}
-                                      <- module_attributes(Module)]
-                      end, Modules),
-    sort_boot_steps(UnsortedSteps).
+    lists:flatmap(fun (Module) ->
+                          [{StepName, Attributes}
+                           || {N, [{StepName, Attributes}]}
+                                  <- module_attributes(Module), N =:= Name]
+                  end, Modules).
+
+boot_steps() ->
+    sort_boot_steps(all_module_attributes(rabbit_boot_step)).
 
 sort_boot_steps(UnsortedSteps) ->
     G = digraph:new([acyclic]),
diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index 577d206d1b..cd072b9cb4 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -44,9 +44,6 @@
 
 -include("rabbit.hrl").
 
--define(SCHEMA_VERSION_SET, []).
--define(SCHEMA_VERSION_FILENAME, "schema_version").
-
 %%----------------------------------------------------------------------------
 
 -ifdef(use_specs).
@@ -94,9 +91,6 @@ init() ->
     ok = ensure_mnesia_running(),
     ok = ensure_mnesia_dir(),
     ok = init_db(read_cluster_nodes_config(), true),
-    ok = rabbit_misc:write_term_file(filename:join(
-                                       dir(), ?SCHEMA_VERSION_FILENAME),
-                                     [?SCHEMA_VERSION_SET]),
     ok.
 
 is_db_empty() ->
@@ -384,6 +378,7 @@ init_db(ClusterNodes, Force) ->
                 [] ->
                     case mnesia:system_info(use_dir) of
                         true ->
+                            rabbit_upgrade:maybe_upgrade(dir()),
                             case check_schema_integrity() of
                                 ok ->
                                     ok;
@@ -428,7 +423,8 @@ create_schema() ->
                           cannot_start_mnesia),
     ok = create_tables(),
     ok = ensure_schema_integrity(),
-    ok = wait_for_tables().
+    ok = wait_for_tables(),
+    ok = rabbit_upgrade:write_version(dir()).
 
 move_db() ->
     mnesia:stop(),
diff --git a/src/rabbit_upgrade.erl b/src/rabbit_upgrade.erl
new file mode 100644
index 0000000000..acefc5b4b1
--- /dev/null
+++ b/src/rabbit_upgrade.erl
@@ -0,0 +1,135 @@
+%%   The contents of this file are subject to the Mozilla Public License
+%%   Version 1.1 (the "License"); you may not use this file except in
+%%   compliance with the License. You may obtain a copy of the License at
+%%   http://www.mozilla.org/MPL/
+%%
+%%   Software distributed under the License is distributed on an "AS IS"
+%%   basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
+%%   License for the specific language governing rights and limitations
+%%   under the License.
+%%
+%%   The Original Code is RabbitMQ.
+%%
+%%   The Initial Developers of the Original Code are LShift Ltd,
+%%   Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
+%%   Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
+%%   are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
+%%   Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created by LShift Ltd are Copyright (C) 2007-2010 LShift
+%%   Ltd. Portions created by Cohesive Financial Technologies LLC are
+%%   Copyright (C) 2007-2010 Cohesive Financial Technologies
+%%   LLC. Portions created by Rabbit Technologies Ltd are Copyright
+%%   (C) 2007-2010 Rabbit Technologies Ltd.
+%%
+%%   All Rights Reserved.
+%%
+%%   Contributor(s): ______________________________________.
+%%
+-module(rabbit_upgrade).
+
+-export([maybe_upgrade/1, write_version/1]).
+
+-include("rabbit.hrl").
+
+-define(SCHEMA_VERSION_FILENAME, "schema_version").
+
+%% API ---------------------------------------------------------------
+
+%% Try to upgrade the schema. If no information on the existing schema could
+%% be found, do nothing. rabbit_mnesia:check_schema_integrity() will catch the
+%% problem.
+%% TODO detect failed upgrades
+maybe_upgrade(Dir) ->
+    case rabbit_misc:read_term_file(schema_filename(Dir)) of
+        {ok, [CurrentHeads]} ->
+            G = load_graph(),
+            case check_unknown_heads(CurrentHeads, G) of
+                ok ->
+                    Upgrades = upgrades_to_apply(CurrentHeads, G),
+                    [apply_upgrade(Upgrade) || Upgrade <- Upgrades],
+                    case length(Upgrades) of
+                        0 -> ok;
+                        _ -> write_version(Dir)
+                    end;
+                _ ->
+                    ok
+            end,
+            digraph:delete(G),
+            ok;
+        {error, enoent} ->
+            ok
+    end.
+
+write_version(Dir) ->
+    G = load_graph(),
+    rabbit_misc:write_term_file(schema_filename(Dir), [heads(G)]),
+    digraph:delete(G).
+
+%% Graphs ------------------------------------------------------------
+
+load_graph() ->
+    G = digraph:new([acyclic]),
+    Upgrades = rabbit:all_module_attributes(rabbit_upgrade),
+    [case digraph:vertex(G, StepName) of
+         false -> digraph:add_vertex(G, StepName, Step);
+         _     -> throw({duplicate_upgrade, StepName})
+     end || Step = {StepName, _Attrs} <- Upgrades],
+
+    lists:foreach(fun ({Upgrade, Attributes}) ->
+                          [add_edges(G, Requires, Upgrade)
+                           || {requires, Requires} <- Attributes]
+                  end, Upgrades),
+    G.
+
+add_edges(G, Requires, Upgrade) ->
+    Results = [digraph:add_edge(G, R, Upgrade) || R <- Requires],
+    case [E || {error, _} = E <- Results] of
+        [] -> ok;
+        L  -> exit(L)
+    end.
+
+check_unknown_heads(Heads, G) ->
+    case [H || H <- Heads, digraph:vertex(G, H) =:= false] of
+        [] ->
+            ok;
+        Unknown ->
+            [warn("Data store has had future upgrade ~w applied. Will not " ++
+                      "upgrade.~n", [U]) || U <- Unknown],
+            Unknown
+    end.
+
+upgrades_to_apply(Heads, G) ->
+    Unsorted = sets:to_list(
+                sets:subtract(
+                  sets:from_list(digraph:vertices(G)),
+                  sets:from_list(digraph_utils:reaching(Heads, G)))),
+    [begin
+         {StepName, Step} = digraph:vertex(G, StepName),
+         Step
+     end || StepName <- digraph_utils:topsort(
+                          digraph_utils:subgraph(G, Unsorted))].
+
+heads(G) ->
+    [V || V <- digraph:vertices(G), digraph:out_degree(G, V) =:= 0].
+
+%% Upgrades-----------------------------------------------------------
+
+apply_upgrade({Name, Props}) ->
+    info("Applying upgrade ~w~n", [Name]),
+    {Module, Function} = proplists:get_value(mf, Props),
+    info("->  ~w:~w~n", [Module, Function]).
+
+%% Utils -------------------------------------------------------------
+
+schema_filename(Dir) ->
+    filename:join(Dir, ?SCHEMA_VERSION_FILENAME).
+
+%% NB: we cannot use rabbit_log here since it may not have been started yet
+info(Msg, Args) ->
+    error_logger:info_msg(Msg, Args).
+
+warn(Msg, Args) ->
+    error_logger:warning_msg(Msg, Args).
diff --git a/src/rabbit_upgrades.erl b/src/rabbit_upgrades.erl
new file mode 100644
index 0000000000..8e962b206c
--- /dev/null
+++ b/src/rabbit_upgrades.erl
@@ -0,0 +1,60 @@
+%%   The contents of this file are subject to the Mozilla Public License
+%%   Version 1.1 (the "License"); you may not use this file except in
+%%   compliance with the License. You may obtain a copy of the License at
+%%   http://www.mozilla.org/MPL/
+%%
+%%   Software distributed under the License is distributed on an "AS IS"
+%%   basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
+%%   License for the specific language governing rights and limitations
+%%   under the License.
+%%
+%%   The Original Code is RabbitMQ.
+%%
+%%   The Initial Developers of the Original Code are LShift Ltd,
+%%   Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
+%%   Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
+%%   are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
+%%   Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created by LShift Ltd are Copyright (C) 2007-2010 LShift
+%%   Ltd. Portions created by Cohesive Financial Technologies LLC are
+%%   Copyright (C) 2007-2010 Cohesive Financial Technologies
+%%   LLC. Portions created by Rabbit Technologies Ltd are Copyright
+%%   (C) 2007-2010 Rabbit Technologies Ltd.
+%%
+%%   All Rights Reserved.
+%%
+%%   Contributor(s): ______________________________________.
+%%
+-module(rabbit_upgrades).
+
+-include("rabbit.hrl").
+
+-compile([export_all]).
+
+-rabbit_upgrade({foo,
+                 [{mf,      {rabbit_upgrades, foo}},
+                  {requires, []}]}).
+
+-rabbit_upgrade({bar,
+                 [{mf,      {rabbit_upgrades, foo}},
+                  {requires, []}]}).
+
+-rabbit_upgrade({remove_user_scope,
+                 [{mf,      {rabbit_upgrades, remove_user_scope}},
+                  {requires, [foo]}]}).
+
+-rabbit_upgrade({remove_user_scope2,
+                 [{mf,      {rabbit_upgrades, foo}},
+                  {requires, [remove_user_scope]}]}).
+
+-rabbit_upgrade({baz,
+                 [{mf,      {rabbit_upgrades, foo}},
+                  {requires, [bar]}]}).
+
+%%--------------------------------------------------------------------
+
+remove_user_scope() ->
+    ok.