Add RandomUpstreamResolver

jDnsProxy/src/main/java/com/moparisthebest/dns/resolve/RandomUpstreamResolver.java

@@ -0,0 +1,31 @@
+package com.moparisthebest.dns.resolve;
+
+import com.moparisthebest.dns.dto.Packet;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomUpstreamResolver implements Resolver {
+
+    private final Resolver[] delegates;
+
+    public RandomUpstreamResolver(final Resolver... delegates) {
+        this.delegates = delegates;
+    }
+
+    public Resolver random() {
+        return delegates[ThreadLocalRandom.current().nextInt(delegates.length)];
+    }
+
+    @Override
+    public <E extends RequestResponse> CompletableFuture<E> resolveAsync(final E requestResponse, final Executor executor) {
+        return random().resolveAsync(requestResponse, executor);
+    }
+
+    @Override
+    public Packet resolve(final Packet request) throws Exception {
+        return random().resolve(request);
+    }
+
+}