Description of problem: When using nscd to cache dns requests, the report created by "nscd -g" isn't accurate. All requests are added in the "cache miss" despite tests show some requests have been cached as appropriate. Version-Release number of selected component (if applicable): nscd-2.28-127.el8 How reproducible: always Steps to Reproduce: 1. dnf install nscd 2. systemctl enable nscd --now 3. Actual results: All requests end in the "cache miss" nscd -g: [...] hosts cache: yes cache is enabled yes cache is persistent yes cache is shared 211 suggested size 216064 total data pool size 728 used data pool size 3600 seconds time to live for positive entries 20 seconds time to live for negative entries 0 cache hits on positive entries 0 cache hits on negative entries 5 cache misses on positive entries 2 cache misses on negative entries 0% cache hit rate 5 current number of cached values 6 maximum number of cached values 1 maximum chain length searched 0 number of delays on rdlock 0 number of delays on wrlock 0 memory allocations failed yes check /etc/hosts for changes Expected results: nscd from el7 works so at least some entries end in cache hit. hosts cache: yes cache is enabled yes cache is persistent yes cache is shared 211 suggested size 216064 total data pool size 2224 used data pool size 3600 seconds time to live for positive entries 20 seconds time to live for negative entries 141411 cache hits on positive entries 113409 cache hits on negative entries 48493 cache misses on positive entries 39466 cache misses on negative entries 74% cache hit rate 15 current number of cached values 375 maximum number of cached values 7 maximum chain length searched 1 number of delays on rdlock 1 number of delays on wrlock 0 memory allocations failed yes check /etc/hosts for changes [...] Additional info: # time getent hosts example.com 2606:2800:220:1:248:1893:25c8:1946 example.com real 0m0,340s user 0m0,000s sys 0m0,002s # time getent hosts example.com 2606:2800:220:1:248:1893:25c8:1946 example.com real 0m0,002s user 0m0,001s sys 0m0,000s
This is a design issue due to how the map-based cache works. The cache is read-only by design, so there is no way to communicate successful lookups to the cache from the client application to nscd.