mod_blocklist: Remove weak cache (and increase default LRU cache size)

Weak tables are said to have suboptimal performance, so we might as well
get replace it with an increased default LRU cache size.

Sorry about the 'and'

plugins/mod_blocklist.lua

@@ -24,19 +24,14 @@ local storage = module:open_store();
 local sessions = prosody.hosts[module.host].sessions;
 local full_sessions = prosody.full_sessions;
 
--- First level cache of blocklists by username.
--- Weak table so may randomly expire at any time.
-local cache = setmetatable({}, { __mode = "v" });
-
--- Second level of caching, keeps a fixed number of items, also anchors
--- items in the above cache.
+-- Cache of blocklists, keeps a fixed number of items.
 --
 -- The size of this affects how often we will need to load a blocklist from
 -- disk, which we want to avoid during routing. On the other hand, we don't
 -- want to use too much memory either, so this can be tuned by advanced
 -- users. TODO use science to figure out a better default, 64 is just a guess.
-local cache_size = module:get_option_integer("blocklist_cache_size", 64, 1);
-local cache2 = require"prosody.util.cache".new(cache_size);
+local cache_size = module:get_option_integer("blocklist_cache_size", 256, 1);
+local blocklist_cache = require"prosody.util.cache".new(cache_size);
 
 local null_blocklist = {};
 
@@ -48,8 +43,7 @@ local function set_blocklist(username, blocklist)
 		return ok, err;
 	end
 	-- Successful save, update the cache
-	cache2:set(username, blocklist);
-	cache[username] = blocklist;
+	blocklist_cache:set(username, blocklist);
 	return true;
 end
 
@@ -86,7 +80,7 @@ if not module:get_option_boolean("migrate_legacy_blocking", true) then
 end
 
 local function get_blocklist(username)
-	local blocklist = cache2:get(username);
+	local blocklist = blocklist_cache:get(username);
 	if not blocklist then
 		if not user_exists(username, module.host) then
 			return null_blocklist;
@@ -98,9 +92,8 @@ local function get_blocklist(username)
 		if not blocklist then
 			blocklist = { [false] = { created = os.time(); }; };
 		end
-		cache2:set(username, blocklist);
+		blocklist_cache:set(username, blocklist);
 	end
-	cache[username] = blocklist;
 	return blocklist;
 end
 
@@ -108,7 +101,7 @@ module:hook("iq-get/self/urn:xmpp:blocking:blocklist", function (event)
 	local origin, stanza = event.origin, event.stanza;
 	local username = origin.username;
 	local reply = st.reply(stanza):tag("blocklist", { xmlns = "urn:xmpp:blocking" });
-	local blocklist = cache[username] or get_blocklist(username);
+	local blocklist = get_blocklist(username);
 	for jid in pairs(blocklist) do
 		if jid then
 			reply:tag("item", { jid = jid }):up();
@@ -167,7 +160,7 @@ local function edit_blocklist(event)
 		return true;
 	end
 
-	local blocklist = cache[username] or get_blocklist(username);
+	local blocklist = get_blocklist(username);
 
 	local new_blocklist = {
 		-- We set the [false] key to something as a signal not to migrate privacy lists
@@ -241,8 +234,7 @@ module:hook("iq-set/self/urn:xmpp:blocking:unblock", edit_blocklist, -1);
 -- Cache invalidation, solved!
 module:hook_global("user-deleted", function (event)
 	if event.host == module.host then
-		cache2:set(event.username, nil);
-		cache[event.username] = nil;
+		blocklist_cache:set(event.username, nil);
 	end
 end);
 
@@ -257,7 +249,7 @@ module:hook("iq-error/self/blocklist-push", function (event)
 end);
 
 local function is_blocked(user, jid)
-	local blocklist = cache[user] or get_blocklist(user);
+	local blocklist = get_blocklist(user);
 	if blocklist[jid] then return true; end
 	local node, host = jid_split(jid);
 	return blocklist[host] or node and blocklist[node..'@'..host];