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%%% Copyright (c) 2014, NORDUnet A/S.
%%% See LICENSE for licensing information.
-module(util).
-export([tempfilename/1, fsync/1, fsync/2, exit_with_error/3,
check_error/3, write_tempfile_and_rename/3,
spawn_and_wait/1, parallel_map/3]).
-include("timeouts.hrl").
-spec tempfilename(string()) -> string().
tempfilename(Base) ->
{MegaSecs, Secs, MicroSecs} = plop_compat:timestamp(),
Filename = io_lib:format("~s-~s-~p.~p", [Base, os:getpid(),
MegaSecs * 1000000 + Secs, MicroSecs]),
Filename.
-spec fsync([string()]) -> ok.
fsync(Paths, Timeout) ->
case fsyncport:fsyncall(Paths, Timeout) of
ok ->
ok;
{error, Error} ->
exit_with_error(fsync, Error, "Error in fsync")
end.
fsync(Paths) ->
fsync(Paths, ?UTIL_FSYNC_DEFAULT_TIMEOUT).
-spec exit_with_error(atom(), atom(), string()) -> no_return().
exit_with_error(Operation, Error, ErrorMessage) ->
io:format("~s(~w): ~w~n", [ErrorMessage, Operation, Error]),
exit({fileerror, Operation, Error, ErrorMessage}).
-spec check_error(any(), atom(), string()) -> ok.
check_error(ReturnValue, Operation, ErrorMessage) ->
case ReturnValue of
ok ->
ok;
{error, Error} ->
exit_with_error(Operation, Error, ErrorMessage)
end.
-spec write_tempfile_and_rename(string(), string(), binary()) -> ok.
write_tempfile_and_rename(Name, NurseryName, Content) ->
case file:open(NurseryName, [write, exclusive]) of
{ok, File} ->
ok = file:write(File, Content),
file:close(File),
check_error(file:rename(NurseryName, Name), rename,
"Error when renaming tempfile to final file");
{error, eexist} ->
%% Should not happen, file name should be unique
exit_with_error(writefile, eexist,
"File existed when creating tempfile");
{error, Error} ->
exit_with_error(writefile, Error,
"Error when creating tempfile")
end.
spawn_and_wait(Fun) ->
ParentPid = self(),
ChildPid = spawn_link(fun () ->
try
Result = Fun(),
ParentPid ! {result, self(), Result}
catch
Type:What ->
[CrashFunction | Stack] = erlang:get_stacktrace(),
lager:error("Crashed process: ~p ~p~n ~p~n ~p~n", [Type, What, CrashFunction, Stack]),
ParentPid ! {result, self(), crash}
end
end),
receive
{result, ChildPid, Result} ->
Result
end.
parallel_map_worker_loop(ParentPid, Fun, N) ->
receive
{parallel_map_request, ParentPid, Input} ->
Result = Fun(Input),
ParentPid ! {parallel_map_result, self(), Result},
parallel_map_worker_loop(ParentPid, Fun, N);
{parallel_map_stop, ParentPid} ->
ok
end.
parallel_map_worker(ParentPid, Fun, N) ->
try
parallel_map_worker_loop(ParentPid, Fun, N)
catch
Type:What ->
[CrashFunction | Stack] = erlang:get_stacktrace(),
lager:error("Crashed process: ~p ~p~n ~p~n ~p~n", [Type, What, CrashFunction, Stack]),
ParentPid ! {parallel_map_crash, self()}
end.
parallel_map_loop([], _FreeChildren, WorkingChildren, Acc) ->
case queue:out(WorkingChildren) of
{{value, FirstChild}, NewWorkingChildren} ->
receive
{parallel_map_result, FirstChild, Result} ->
parallel_map_loop([], [FirstChild], NewWorkingChildren, [Result | Acc]);
{parallel_map_crash, FirstChild} ->
crash
end;
{empty, _} ->
Acc
end;
parallel_map_loop(Items, [], WorkingChildren, Acc) ->
{{value, FirstChild}, NewWorkingChildren} = queue:out(WorkingChildren),
receive
{parallel_map_result, FirstChild, Result} ->
parallel_map_loop(Items, [FirstChild], NewWorkingChildren, [Result | Acc]);
{parallel_map_crash, FirstChild} ->
crash
end;
parallel_map_loop([Item|Rest], [FreeChild|FreeChildren], WorkingChildren, Acc) ->
FreeChild ! {parallel_map_request, self(), Item},
parallel_map_loop(Rest, FreeChildren, queue:in(FreeChild, WorkingChildren), Acc).
parallel_map(Fun, List, 1) ->
lists:map(Fun, List);
parallel_map(Fun, List, Parallel) ->
ParentPid = self(),
ChildPids = lists:map(fun(N) ->
spawn_link(fun () ->
parallel_map_worker(ParentPid, Fun, N)
end)
end, lists:seq(1, Parallel)),
case parallel_map_loop(List, ChildPids, queue:new(), []) of
crash ->
exit(crash);
Result ->
lists:foreach(fun (Child) ->
Child ! {parallel_map_stop, self()}
end, ChildPids),
lists:reverse(Result)
end.
%%%%%%%%%%%%%%%%%%%%
-include_lib("eunit/include/eunit.hrl").
fact(N) ->
fact(N, 1).
fact(1, Acc) ->
Acc;
fact(N, Acc) ->
fact(N - 1, Acc * N).
parallel_map_test() ->
Result1 = lists:map(fun fact/1, lists:seq(1, 2000)),
Result2 = parallel_map(fun fact/1, lists:seq(1, 2000), 10),
?assertEqual(Result1, Result2).
|
