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%% 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 Rabbit Technologies Ltd.
%%
%% Copyright (C) 2010 Rabbit Technologies Ltd.
%%
%% All Rights Reserved.
%%
%% Contributor(s): ______________________________________.
%%
-module(rabbit_upgrade).
-export([maybe_upgrade/0, read_version/0, write_version/0, desired_version/0]).
-include("rabbit.hrl").
-define(VERSION_FILENAME, "schema_version").
-define(LOCK_FILENAME, "schema_upgrade_lock").
%% -------------------------------------------------------------------
-ifdef(use_specs).
-spec(maybe_upgrade/0 :: () -> 'ok' | 'version_not_available').
-spec(read_version/0 ::
() -> {'ok', [any()]} | rabbit_types:error(any())).
-spec(write_version/0 :: () -> 'ok').
-spec(desired_version/0 :: () -> [any()]).
-endif.
%% -------------------------------------------------------------------
%% 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.
maybe_upgrade() ->
case read_version() of
{ok, CurrentHeads} ->
G = load_graph(),
case unknown_heads(CurrentHeads, G) of
[] ->
case upgrades_to_apply(CurrentHeads, G) of
[] -> ok;
Upgrades -> apply_upgrades(Upgrades)
end;
Unknown ->
exit({future_upgrades_found, Unknown})
end,
true = digraph:delete(G),
ok;
{error, enoent} ->
version_not_available
end.
read_version() ->
case rabbit_misc:read_term_file(schema_filename()) of
{ok, [Heads]} -> {ok, Heads};
{error, E} -> {error, E}
end.
write_version() ->
ok = rabbit_misc:write_term_file(schema_filename(), [desired_version()]),
ok.
desired_version() ->
G = load_graph(),
Version = heads(G),
true = digraph:delete(G),
Version.
%% -------------------------------------------------------------------
load_graph() ->
Upgrades = rabbit_misc:all_module_attributes(rabbit_upgrade),
rabbit_misc:build_acyclic_graph(
fun vertices/2, fun edges/2, fun graph_build_error/1, Upgrades).
vertices(Module, Steps) ->
[{StepName, {Module, StepName}} || {StepName, _Reqs} <- Steps].
edges(_Module, Steps) ->
[{Require, StepName} || {StepName, Requires} <- Steps, Require <- Requires].
graph_build_error({vertex, duplicate, StepName}) ->
exit({duplicate_upgrade, StepName});
graph_build_error({edge, E, From, To}) ->
exit({E, From, To}).
unknown_heads(Heads, G) ->
[H || H <- Heads, digraph:vertex(G, H) =:= false].
upgrades_to_apply(Heads, G) ->
%% Take all the vertices which can reach the known heads. That's
%% everything we've already applied. Subtract that from all
%% vertices: that's what we have to apply.
Unsorted = sets:to_list(
sets:subtract(
sets:from_list(digraph:vertices(G)),
sets:from_list(digraph_utils:reaching(Heads, G)))),
%% Form a subgraph from that list and find a topological ordering
%% so we can invoke them in order.
[element(2, digraph:vertex(G, StepName))
|| StepName <- digraph_utils:topsort(digraph_utils:subgraph(G, Unsorted))].
heads(G) ->
lists:sort([V || V <- digraph:vertices(G), digraph:out_degree(G, V) =:= 0]).
%% -------------------------------------------------------------------
apply_upgrades(Upgrades) ->
LockFile = lock_filename(),
case file:open(LockFile, [write, exclusive]) of
{ok, Lock} ->
ok = file:close(Lock),
info("Upgrades: ~w to apply~n", [length(Upgrades)]),
[apply_upgrade(Upgrade) || Upgrade <- Upgrades],
info("Upgrades: All applied~n", []),
ok = write_version(),
ok = file:delete(LockFile);
{error, eexist} ->
exit(previous_upgrade_failed);
{error, _} = Error ->
exit(Error)
end.
apply_upgrade({M, F}) ->
info("Upgrades: Applying ~w:~w~n", [M, F]),
ok = apply(M, F, []).
%% -------------------------------------------------------------------
schema_filename() ->
filename:join(dir(), ?VERSION_FILENAME).
lock_filename() ->
filename:join(dir(), ?LOCK_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).
dir() ->
rabbit_mnesia:dir().
|
