DefaultDnsCache Class — netty Architecture

Source Code

resolver-dns/src/main/java/io/netty/resolver/dns/DefaultDnsCache.java lines 41–329

public class DefaultDnsCache implements DnsCache {

    private final Cache<DefaultDnsCacheEntry> resolveCache = new Cache<DefaultDnsCacheEntry>() {

        @Override
        protected boolean shouldReplaceAll(DefaultDnsCacheEntry entry) {
            return entry.cause() != null;
        }

        @Override
        protected boolean equals(DefaultDnsCacheEntry entry, DefaultDnsCacheEntry otherEntry) {
            if (entry.address() != null) {
                return entry.address().equals(otherEntry.address());
            }
            if (otherEntry.address() != null) {
                return false;
            }
            return entry.cause().equals(otherEntry.cause());
        }
    };

    private final int minTtl;
    private final int maxTtl;
    private final int negativeTtl;

    /**
     * Create a cache that respects the TTL returned by the DNS server
     * and doesn't cache negative responses.
     */
    public DefaultDnsCache() {
        this(0, Cache.MAX_SUPPORTED_TTL_SECS, 0);
    }

    /**
     * Create a cache.
     * @param minTtl the minimum TTL
     * @param maxTtl the maximum TTL
     * @param negativeTtl the TTL for failed queries
     */
    public DefaultDnsCache(int minTtl, int maxTtl, int negativeTtl) {
        this.minTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(minTtl, "minTtl"));
        this.maxTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(maxTtl, "maxTtl"));
        if (minTtl > maxTtl) {
            throw new IllegalArgumentException(
                    "minTtl: " + minTtl + ", maxTtl: " + maxTtl + " (expected: 0 <= minTtl <= maxTtl)");
        }
        this.negativeTtl = Math.min(Cache.MAX_SUPPORTED_TTL_SECS, checkPositiveOrZero(negativeTtl, "negativeTtl"));
    }

    /**
     * Returns the minimum TTL of the cached DNS resource records (in seconds).
     *
     * @see #maxTtl()
     */
    public int minTtl() {
        return minTtl;
    }

    /**
     * Returns the maximum TTL of the cached DNS resource records (in seconds).
     *
     * @see #minTtl()
     */
    public int maxTtl() {
        return maxTtl;
    }

    /**
     * Returns the TTL of the cache for the failed DNS queries (in seconds). The default value is {@code 0}, which
     * disables the cache for negative results.
     */
    public int negativeTtl() {
        return negativeTtl;
    }

    @Override
    public void clear() {
        resolveCache.clear();
    }

    @Override