From 8920afaf2fb1d0b724f9528d009c0bc226c3adbc Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Sun, 6 Dec 2015 02:09:52 +0100
Subject: mod_blocklist: Expand comments on caching of blocklists
---
plugins/mod_blocklist.lua | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/plugins/mod_blocklist.lua b/plugins/mod_blocklist.lua
index add7abb3..a38d2a0f 100644
--- a/plugins/mod_blocklist.lua
+++ b/plugins/mod_blocklist.lua
@@ -19,11 +19,17 @@ local jid_split = require"util.jid".split;
local storage = module:open_store();
local sessions = prosody.hosts[module.host].sessions;
--- Cache of blocklists by username may randomly expire at any time
+-- 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
+-- Second level of caching, keeps a fixed number of items, also anchors
+-- items in the above cache.
+--
+-- 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_number("blocklist_cache_size", 64);
local cache2 = require"util.cache".new(cache_size);
--
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