Apache Ignite discovery for Rancher

TcpDiscoveryRancherIpFinder.java

import org.apache.ignite.internal.IgniteInterruptedCheckedException;
import org.apache.ignite.internal.util.typedef.internal.U;
import org.apache.ignite.spi.IgniteSpiException;
import org.apache.ignite.spi.discovery.tcp.ipfinder.TcpDiscoveryIpFinderAdapter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;


public class TcpDiscoveryRancherIpFinder extends TcpDiscoveryIpFinderAdapter {

    private Logger log = LoggerFactory.getLogger("TcpDiscoveryRancherIpFinder");

    private URL url;

    private final AtomicBoolean initGuard = new AtomicBoolean();

    private final CountDownLatch initLatch = new CountDownLatch(1);

    public TcpDiscoveryRancherIpFinder() {
        setShared(true);
    }

    private String getServiceNameFromMeta() throws IOException {
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.setRequestMethod("GET");

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), "UTF-8"));

        String result = "";
        String line;

        while ((line = bufferedReader.readLine()) != null) {
            result += line;
        }
        bufferedReader.close();
        return result;
    }

    @Override
    public Collection<InetSocketAddress> getRegisteredAddresses() throws IgniteSpiException {
        init();

        Collection<InetSocketAddress> addrs = new ArrayList<>();

        try {
            String serviceNameInRancherStack = getServiceNameFromMeta().trim();
            if (log.isDebugEnabled())
                log.debug("Getting Apache Ignite endpoints from: " + serviceNameInRancherStack);

            InetAddress[] addresses = InetAddress.getAllByName(serviceNameInRancherStack);

            for (InetAddress address : addresses) {
                if (log.isDebugEnabled())
                    log.debug("Added an address to the list: " + address.getHostAddress());

                addrs.add(InetSocketAddress.createUnresolved(address.getHostAddress(), 0));
            }
        } catch (Exception e) {
            throw new IgniteSpiException("Failed to retrieve Ignite pods IP addresses.", e);
        }

        return addrs;
    }

    private void init() throws IgniteSpiException {
        if (initGuard.compareAndSet(false, true)) {
            try {
                url = new URL("http://rancher-metadata/2015-12-19/self/service/name");
            } catch (Exception e) {
                throw new IgniteSpiException("Failed to connect to Ignite's Kubernetes Service.", e);
            } finally {
                initLatch.countDown();
            }
        } else {
            try {
                U.await(initLatch);
            } catch (IgniteInterruptedCheckedException e) {
                throw new IgniteSpiException("Thread has been interrupted.", e);
            }

            if (url == null)
                throw new IgniteSpiException("RancherIp finder has not been initialized properly.");
        }
    }

    @Override
    public void registerAddresses(Collection<InetSocketAddress> addrs) throws IgniteSpiException {
        // No-op
    }

    @Override
    public void unregisterAddresses(Collection<InetSocketAddress> addrs) throws IgniteSpiException {
        // No-op
    }
}

Apache Ignite discovery for Rancher, without external dependence.