node-repository/src/main/java/com/yahoo/vespa/hosted/provision/testutils/MockNameResolver.java


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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.provision.testutils;

import com.google.common.collect.ImmutableSet;
import com.yahoo.vespa.hosted.provision.persistence.NameResolver;

import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;

/**
 * A mock DNS resolver. Can be configured to only answer specific lookups or any lookup.
 *
 * @author mpolden
 */
public class MockNameResolver implements NameResolver {

    private boolean allowInvocation = true;
    private boolean mockAnyLookup = false;
    private final Map<String, Set<String>> records = new HashMap<>();

    public MockNameResolver addRecord(String hostname, String... ipAddress) {
        Arrays.stream(ipAddress).forEach(Objects::requireNonNull);
        records.put(hostname, ImmutableSet.copyOf(ipAddress));
        return this;
    }

    public MockNameResolver reset() {
        this.allowInvocation = true;
        this.mockAnyLookup = false;
        this.records.clear();
        return this;
    }

    public MockNameResolver failIfInvoked() {
        this.allowInvocation = false;
        return this;
    }

    public MockNameResolver mockAnyLookup() {
        this.mockAnyLookup = true;
        return this;
    }

    @Override
    public Set<String> getAllByNameOrThrow(String hostname) {
        if (!allowInvocation) {
            throw new IllegalStateException("Expected getAllByName to not be invoked for hostname: " + hostname);
        }
        if (records.containsKey(hostname)) {
            return records.get(hostname);
        }
        if (mockAnyLookup) {
            Set<String> ipAddresses = Collections.singleton(randomIpAddress());
            records.put(hostname, ipAddresses);
            return ipAddresses;
        }
        throw new RuntimeException(new UnknownHostException("Could not resolve: " + hostname));
    }

    @Override
    public Optional<String> getHostname(String ipAddress) {
        for (String host : records.keySet()) {
            if (records.get(host).contains(ipAddress)) return Optional.of(host);
        }
        return Optional.empty();
    }

    private static String randomIpAddress() {
        // Generate a random IP in 127/8 (loopback block)
        ThreadLocalRandom random = ThreadLocalRandom.current();
        return String.format("127.%d.%d.%d",
                random.nextInt(1, 255 + 1),
                random.nextInt(1, 255 + 1),
                random.nextInt(1, 255 + 1));
    }
}