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fix(dsrepl): turn memoize into a safer function

This commit is contained in:
Andrew Mayorov 2024-03-19 15:58:13 +01:00
parent d39ca41070
commit a1f5de3f5b
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1 changed files with 15 additions and 13 deletions
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28
apps/emqx_durable_storage/src/emqx_ds_replication_layer_shard.erl
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@ -38,17 +38,6 @@
terminate/2
]).
-define(PTERM(DB, SHARD, L), {?MODULE, DB, SHARD, L}).
-define(MEMOIZE(DB, SHARD, EXPR),
case persistent_term:get(__X_Key = ?PTERM(DB, SHARD, ?LINE), undefined) of
undefined ->
ok = persistent_term:put(__X_Key, __X_Value = (EXPR)),
__X_Value;
__X_Value ->
__X_Value
end
).
%%
start_link(DB, Shard, Opts) ->
@ -121,10 +110,10 @@ pick_random(Servers) ->
lists:nth(rand:uniform(length(Servers)), Servers).
get_cluster_name(DB, Shard) ->
?MEMOIZE(DB, Shard, cluster_name(DB, Shard)).
memoize(fun cluster_name/2, [DB, Shard]).
get_local_server(DB, Shard) ->
?MEMOIZE(DB, Shard, local_server(DB, Shard)).
memoize(fun local_server/2, [DB, Shard]).
get_shard_servers(DB, Shard) ->
maps:get(servers, emqx_ds_replication_shard_allocator:shard_meta(DB, Shard)).
@ -203,3 +192,16 @@ start_shard(DB, Shard, #{replication_options := ReplicationOpts}) ->
servers => Servers,
local_server => LocalServer
}.
%%
memoize(Fun, Args) ->
%% NOTE: Assuming that the function is pure and never returns `undefined`.
case persistent_term:get([Fun | Args], undefined) of
undefined ->
Result = erlang:apply(Fun, Args),
_ = persistent_term:put([Fun | Args], Result),
Result;
Result ->
Result
end.