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replace simple IP pool free table with LRU implementation #451

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Oct 27, 2021
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28 changes: 12 additions & 16 deletions apps/ergw_core/src/ergw_local_pool.erl
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@
terminate/2, code_change/3]).

-record(state, {name, pools, ipv4_opts, ipv6_opts}).
-record(pool, {name, type, id, base, size, first, last, shift, used, free, used_pool, free_pool}).
-record(pool, {name, type, id, base, size, first, last, shift, used, free, used_pool, free_lru}).
-record(lease, {ip, client_id}).

-include_lib("kernel/include/logger.hrl").
Expand Down Expand Up @@ -193,10 +193,10 @@ init_pools(Name, Ranges) ->
Pools
end, #{}, Ranges).

init_table(Tid, Start, End) ->
init_free_lru(Start, End) ->
Length = End - Start + 1,
IPsList = uint32_fy_shuffle:shuffle(Length),
true = ets:insert(Tid, IPsList).
lru:from_list(IPsList).

handle_call({get, ClientId, Type, PrefixLen, ReqOpts}, _From, #state{pools = Pools} = State)
when is_atom(Type), is_map_key({Type, PrefixLen}, Pools) ->
Expand Down Expand Up @@ -276,14 +276,13 @@ alloc_reply({error, _} = Error, _, _) ->

init_pool(Name, Type, First, Last, Shift) ->
UsedTid = ets:new(used_pool, [set, {keypos, #lease.ip}]),
FreeTid = ets:new(free_pool, [ordered_set]),

Id = inet:ntoa(int2ip(Type, First)),
Start = First bsr Shift,
End = Last bsr Shift,
Size = End - Start + 1,
?LOG(debug, "init Pool ~w ~p - ~p (~p)", [Id, Start, End, Size]),
init_table(FreeTid, Start, End),
FreeLRU = init_free_lru(Start, End),

prometheus_gauge:declare([{name, ergw_local_pool_free},
{labels, [name, type, id]},
Expand All @@ -297,20 +296,19 @@ init_pool(Name, Type, First, Last, Shift) ->
base = Start, size = Size,
first = First, last = Last, shift = Shift,
used = 0, free = Size,
used_pool = UsedTid, free_pool = FreeTid},
used_pool = UsedTid, free_lru = FreeLRU},
metrics_sync_gauges(Pool),
?LOG(debug, "init Pool state: ~p", [Pool]),
Pool.

allocate_ip(ClientId, ReqOpts,
#pool{base = Base,
used = Used, free = Free,
used_pool = UsedTid, free_pool = FreeTid} = Pool0)
used_pool = UsedTid, free_lru = FreeLRU} = Pool0)
when Free =/= 0 ->
?LOG(debug, "~w: Allocate Pool: ~p", [self(), Pool0]),

{_, Id} = Key = ets:first(FreeTid),
ets:delete(FreeTid, Key),
{ok, Id} = lru:pop(FreeLRU),
ets:insert(UsedTid, #lease{ip = Id, client_id = ClientId}),
IP = id2ip(Base + Id, ReqOpts, Pool0),
Pool = Pool0#pool{used = Used + 1, free = Free - 1},
Expand All @@ -322,14 +320,13 @@ allocate_ip(_ClientId, _ReqOpts, Pool) ->
release_ip(IP, #pool{base = Base, first = First, last = Last,
shift = Shift,
used = Used, free = Free,
used_pool = UsedTid, free_pool = FreeTid} = Pool0)
used_pool = UsedTid, free_lru = FreeLRU} = Pool0)
when IP >= First andalso IP =< Last ->
Id = (IP bsr Shift) - Base,

case ets:take(UsedTid, Id) of
[_] ->
Now = erlang:monotonic_time(),
ets:insert(FreeTid, {{Now, Id}}),
lru:push(Id, FreeLRU),
Pool = Pool0#pool{used = Used - 1, free = Free + 1},
metrics_sync_gauges(Pool),
Pool;
Expand All @@ -348,13 +345,12 @@ take_ip(ClientId, IP, ReqOpts,
#pool{base = Base, first = First, last = Last,
shift = Shift,
used = Used, free = Free,
used_pool = UsedTid, free_pool = FreeTid} = Pool0)
used_pool = UsedTid, free_lru = FreeLRU} = Pool0)
when IP >= First andalso IP =< Last ->
Id = (IP bsr Shift) - Base,

case ets:match_object(FreeTid, {{'_', Id}}) of
[{Key}] ->
ets:delete(FreeTid, Key),
case lru:take(Id, FreeLRU) of
ok ->
ets:insert(UsedTid, #lease{ip = Id, client_id = ClientId}),
Pool = Pool0#pool{used = Used + 1, free = Free - 1},
metrics_sync_gauges(Pool),
Expand Down
66 changes: 66 additions & 0 deletions apps/ergw_core/src/lru.erl
Original file line number Diff line number Diff line change
@@ -0,0 +1,66 @@
%% Copyright 2021, Travelping GmbH <[email protected]>

%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License
%% as published by the Free Software Foundation; either version
%% 2 of the License, or (at your option) any later version.

%% ets LRU cache for IP pools, scales to at least 2^24 entries.

-module(lru).

-record(lru, {queue, index}).

-export([from_list/1, to_list/1,
pop/1, push/2, take/2,
valid/1, info/1]).

-ignore_xref([?MODULE]).

from_list([{{_, _}}|_] = List) ->
Queue = ets:new(entries, [ordered_set]),
Index = ets:new(index, [set]),

IndexList = [{Key, QEntry} || {{_, Key} = QEntry} <- List],

true = ets:insert(Queue, List),
true = ets:insert(Index, IndexList),
#lru{queue = Queue, index = Index}.

to_list(#lru{queue = Queue}) ->
ets:tab2list(Queue).

pop(#lru{queue = Queue, index = Index}) ->
case ets:first(Queue) of
{_, Key} = Entry ->
ets:delete(Queue, Entry),
ets:delete(Index, Key),
{ok, Key};
'$end_of_table' ->
{error, empty}
end.

push(Key, #lru{queue = Queue, index = Index}) ->
Now = erlang:monotonic_time(),
case ets:insert_new(Index, {Key, Now}) of
true ->
ets:insert(Queue, {{Now, Key}}),
ok;
false ->
erlang:error(badarg, [Key])
end.

take(Key, #lru{queue = Queue, index = Index}) ->
case ets:take(Index, Key) of
[{_, QEntry}] ->
ets:delete(Queue, QEntry),
ok;
_ ->
{error, not_found}
end.

valid(#lru{queue = Queue, index = Index}) ->
ets:info(Queue, size) =:= ets:info(Index, size).

info(#lru{queue = Queue, index = Index}) ->
{ets:info(Queue, size), ets:info(Index, size)}.