public static String dnsCacheSpec() {
        return DNS_CACHE_SPEC;
    }
Returns the {@linkplain CaffeineSpec Caffeine specification string} of the cache that stores the
domain names and their resolved addresses. This value is used as the default of
{@link DnsResolverGroupBuilder#cacheSpec(String)}.

<p>The default value of this flag is {@value DefaultFlagsProvider#DNS_CACHE_SPEC}. Specify the
{@code -Dcom.linecorp.armeria.dnsCacheSpec=<spec>} JVM option to override the default value.
For example, {@code -Dcom.linecorp.armeria.dnsCacheSpec=maximumSize=1024,expireAfterAccess=600s}.

<p>This cache cannot be disabled with {@code "off"} unlike other cache specification flags.
core/src/main/java/com/linecorp/armeria/common/Flags.java