@Nullable
    public static String routeDecoratorCacheSpec() {
        return ROUTE_DECORATOR_CACHE_SPEC;
    }
Returns the {@linkplain CaffeineSpec Caffeine specification string} of the cache that stores the recent
request routing history for all route decorators.

<p>The default value of this flag is {@value DefaultFlagsProvider#ROUTE_DECORATOR_CACHE_SPEC}. Specify
the {@code -Dcom.linecorp.armeria.routeDecoratorCache=<spec>} JVM option to override the default value.
For example, {@code -Dcom.linecorp.armeria.routeDecoratorCache=maximumSize=4096,expireAfterAccess=600s}.
Also, specify {@code -Dcom.linecorp.armeria.routeDecoratorCache=off} JVM option to disable it.
core/src/main/java/com/linecorp/armeria/common/Flags.java