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Diffstat (limited to 'src/rabbit_upgrade.erl')
| -rw-r--r-- | src/rabbit_upgrade.erl | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/src/rabbit_upgrade.erl b/src/rabbit_upgrade.erl new file mode 100644 index 00000000..0071a08a --- /dev/null +++ b/src/rabbit_upgrade.erl @@ -0,0 +1,156 @@ +%% 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 :: () -> [atom()]). + +-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). + +dir() -> + rabbit_mnesia:dir(). |