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Reduce the default value for max-stale-ttl from 1 week to 12 hours

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Originally, the default value for max-stale-ttl was 1 week, which could
and in some scenarios lead to cache exhaustion on a busy resolvers.
Picking the default value will always be juggling between value that's
useful (e.g. keeping the already cached records after they have already
expired and the upstream name servers are down) and not bloating the
cache too much (e.g. keeping everything for a very long time).  The new
default reflects what we think is a reasonable to time to react on both
sides (upstream authoritative and downstream recursive).
This commit is contained in:
Ondřej Surý 2020-05-27 17:48:39 +02:00
parent b1dc79b5d7
commit 13fd3ecfab
3 changed files with 7 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
bin/named/config.c
View file

@ -170,7 +170,7 @@ options {\n\
max-ncache-ttl 10800; /* 3 hours */\n\
max-recursion-depth 7;\n\
max-recursion-queries 75;\n\
max-stale-ttl 604800; /* 1 week */\n\
max-stale-ttl 43200; /* 12 hours */\n\
message-compression yes;\n\
min-ncache-ttl 0; /* 0 hours */\n\
min-cache-ttl 0; /* 0 seconds */\n\

8
bin/tests/system/serve-stale/tests.sh
View file

@ -21,6 +21,8 @@ waitfile () {
done
}
max_stale_ttl=$(sed -ne 's,^[[:space:]]*max-stale-ttl \([[:digit:]]*\).*,\1,p' $TOP_SRCDIR/bin/named/config.c)
status=0
n=0
@ -723,7 +725,7 @@ n=$((n+1))
echo_i "check 'rndc serve-stale status' ($n)"
ret=0
$RNDCCMD 10.53.0.3 serve-stale status > rndc.out.test$n 2>&1 || ret=1
grep '_default: off (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
grep "_default: off (stale-answer-ttl=1 max-stale-ttl=$max_stale_ttl)" rndc.out.test$n > /dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status+ret))
@ -804,7 +806,7 @@ n=$((n+1))
echo_i "check 'rndc serve-stale status' ($n)"
ret=0
$RNDCCMD 10.53.0.3 serve-stale status > rndc.out.test$n 2>&1 || ret=1
grep '_default: on (rndc) (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
grep "_default: on (rndc) (stale-answer-ttl=1 max-stale-ttl=$max_stale_ttl)" rndc.out.test$n > /dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status+ret))
@ -951,7 +953,7 @@ n=$((n+1))
echo_i "check 'rndc serve-stale status' ($n)"
ret=0
$RNDCCMD 10.53.0.4 serve-stale status > rndc.out.test$n 2>&1 || ret=1
grep '_default: off (stale-answer-ttl=1 max-stale-ttl=604800)' rndc.out.test$n > /dev/null || ret=1
grep "_default: off (stale-answer-ttl=1 max-stale-ttl=$max_stale_ttl)" rndc.out.test$n > /dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status+ret))

2
doc/arm/reference.rst
View file

@ -3264,7 +3264,7 @@ Tuning
If stale answers are enabled, ``max-stale-ttl`` sets the maximum time
for which the server retains records past their normal expiry to
return them as stale records, when the servers for those records are
not reachable. The default is 1 week. The minimum allowed is 1
not reachable. The default is 12 hours. The minimum allowed is 1
second; a value of 0 is updated silently to 1 second.
For stale answers to be returned, they must be enabled, either in the