DnsQueryContextManager Class — netty Architecture

Source Code

resolver-dns/src/main/java/io/netty/resolver/dns/DnsQueryContextManager.java lines 31–190

final class DnsQueryContextManager {

    /**
     * A map whose key is the DNS server address and value is the map of the DNS query ID and its corresponding
     * {@link DnsQueryContext}.
     */
    private final Map<InetSocketAddress, DnsQueryContextMap> map =
            new HashMap<InetSocketAddress, DnsQueryContextMap>();

    /**
     * Add {@link DnsQueryContext} to the context manager and return the ID that should be used for the query.
     * This method will return {@code -1} if an ID could not be generated and the context was not stored.
     *
     * @param nameServerAddr    The {@link InetSocketAddress} of the nameserver to query.
     * @param qCtx              The {@link {@link DnsQueryContext} to store.
     * @return                  the ID that should be used or {@code -1} if none could be generated.
     */
    int add(InetSocketAddress nameServerAddr, DnsQueryContext qCtx) {
        assert !nameServerAddr.isUnresolved();
        final DnsQueryContextMap contexts = getOrCreateContextMap(nameServerAddr);
        return contexts.add(qCtx);
    }

    /**
     * Return the {@link DnsQueryContext} for the given {@link InetSocketAddress} and id or {@code null} if
     * none could be found.
     *
     * @param nameServerAddr    The {@link InetSocketAddress} of the nameserver.
     * @param id                The id that identifies the {@link DnsQueryContext} and was used for the query.
     * @return                  The context or {@code null} if none could be found.
     */
    DnsQueryContext get(InetSocketAddress nameServerAddr, int id) {
        assert !nameServerAddr.isUnresolved();
        final DnsQueryContextMap contexts = getContextMap(nameServerAddr);
        if (contexts == null) {
            return null;
        }
        return contexts.get(id);
    }

    /**
     * Remove the {@link DnsQueryContext} for the given {@link InetSocketAddress} and id or {@code null} if
     * none could be found.
     *
     * @param nameServerAddr    The {@link InetSocketAddress} of the nameserver.
     * @param id                The id that identifies the {@link DnsQueryContext} and was used for the query.
     * @return                  The context or {@code null} if none could be removed.
     */
    DnsQueryContext remove(InetSocketAddress nameServerAddr, int id) {
        assert !nameServerAddr.isUnresolved();
        final DnsQueryContextMap contexts = getContextMap(nameServerAddr);
        if (contexts == null) {
            return null;
        }
        return contexts.remove(id);
    }

    private DnsQueryContextMap getContextMap(InetSocketAddress nameServerAddr) {
        synchronized (map) {
            return map.get(nameServerAddr);
        }
    }

    private DnsQueryContextMap getOrCreateContextMap(InetSocketAddress nameServerAddr) {
        synchronized (map) {
            final DnsQueryContextMap contexts = map.get(nameServerAddr);
            if (contexts != null) {
                return contexts;
            }

            final DnsQueryContextMap newContexts = new DnsQueryContextMap();
            final InetAddress a = nameServerAddr.getAddress();
            final int port = nameServerAddr.getPort();
            DnsQueryContextMap old = map.put(nameServerAddr, newContexts);
            // Assert that we didn't replace an existing mapping.
            assert old == null : "DnsQueryContextMap already exists for " + nameServerAddr;

            InetSocketAddress extraAddress = null;
            if (a instanceof Inet4Address) {
                // Also add the mapping for the IPv4-compatible IPv6 address.
                final Inet4Address a4 = (Inet4Address) a;