[dnsdist] dnsdist cache behaviour

[Nicolas Baumgarten]

Hello everybody!

Just a question about dnsdist cache.

We are using dnsdist 1.3.2 (Lua 5.1.4 [LuaJIT 2.0.4]) (soon to be upgraded)
Everything is OK, the software is really amazing.

But we noticed that the cache size never grows to more than 1.000.000
entries
when defined with 2.000.000.
-- newPacketCache(maxEntries, maxTTL, minTTL, temporaryFailureTTL,
staleTTL,
--                dontAge, numberOfShards=1, deferrableInsertLock,
maxNegativeTTL,
--                parseECS)
--
cache = newPacketCache(2000000, 86400, 0, 60, 60, false, 50, true, 3600,
false)
getPool("dnsdist1"):setCache(cache)
setCacheCleaningDelay(30)
setCacheCleaningPercentage(50)
---

getPool("dnsdist1"):getCache():printStats()
Entries: 1002367/2000000
Hits: 178033837243
Misses: 5940352865
Deferred inserts: 6759101
Deferred lookups: 5996490
Lookup Collisions: 2702166
Insert Collisions: 2694733
TTL Too Shorts: 0

I guess it is because of the CleaningPercentage.
But a lot of queries for common names are hitting continuously the backends.
Is this OK? or are we missing something?


by the way doing a cache dump, approximately 40% of the cached entries are
for
things like
1304dd8f8c9431017eae60aea501e699.safeframe.googlesyndication.com

Another 10/15% is filled with non existent domains of the form:
^\D\d{1,2}\.\w{7,8}\.VALID_TLD

x41.bsalbter.com. 472 A ; key 3525880950, length 107, tcp 0, added
1596392916
x20.tbczxiaq.com. 472 A ; key 795603800, length 107, tcp 0, added 1596392916
x23.yqnzycmp.com. 478 A ; key 2431117350, length 107, tcp 0, added
1596392916
x12.ypdlsrbi.com. 478 A ; key 2382591550, length 107, tcp 0, added
1596392916
x18.wnthonmk.com. 478 A ; key 1798655850, length 107, tcp 0, added
1596392916
x21.nblwbsby.com. 466 A ; key 2128294150, length 107, tcp 0, added
1596392916
v1.lslactz.ru. 2894 A ; key 1109072900, length 92, tcp 0, added 1596392787
m32.sfeypxe.com. 348 A ; key 259989300, length 106, tcp 0, added 1596392786
m11.harsnic.biz. 202 A ; key 1089372650, length 95, tcp 0, added 1596392785
m7.tzupwhz.me. 289 A ; key 490917700, length 94, tcp 0, added 1596392784
v1.ycslqlb.ru. 2893 A ; key 3865901600, length 92, tcp 0, added 1596392784
m6.yplcble.in. 292 A ; key 2827817050, length 90, tcp 0, added 1596392784
m7.dqugfga.me. 287 A ; key 576735950, length 94, tcp 0, added 1596392784
m14.tgdhtja.me. 287 A ; key 1459131250, length 95, tcp 0, added 1596392784
x26.qtsfmxxc.com. 466 A ; key 917524100, length 107, tcp 0, added 1596392916
x24.qqoaiyco.com. 472 A ; key 1614099600, length 107, tcp 0, added
1596392916
x11.jnpkzyng.com. 472 A ; key 2952753050, length 107, tcp 0, added
1596392916
x36.hjpuyqbs.com. 466 A ; key 2226816950, length 107, tcp 0, added
1596392916
x20.tplseaex.com. 478 A ; key 4177227850, length 107, tcp 0, added
1596392916
x40.bimnsaft.info. 423 A ; key 2839519700, length 95, tcp 0, added
1596392916
m34.oqemwbj.in. 188 A ; key 1332411900, length 48, tcp 0, added 1596393226
m42.xwzfulh.net. 472 A ; key 1304122150, length 106, tcp 0, added 1596392915
x10.ltazujoq.com. 472 A ; key 1059611600, length 107, tcp 0, added
1596392915
x22.pomsraxu.com. 466 A ; key 2094951400, length 107, tcp 0, added
1596392915
x15.bgohqmeu.com. 477 A ; key 3199526650, length 107, tcp 0, added
1596392915

Anybody knows who is generating this queries (the last ones, obviously the
other are form google)


Many thanks in advance!
Nicolás Baumgarten
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