etcd.client.ServerList Maven / Gradle / Ivy

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package etcd.client;

import java.net.URI;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

class ServerList {

	public static final long DEFAULT_FAILURE_BACKOFF_TIME = TimeUnit.SECONDS.toMillis(2);

	private final ArrayList primaryServers = new ArrayList<>();
	private final ArrayList secondaryServers = new ArrayList<>();

	private final long failureBackoffTime = DEFAULT_FAILURE_BACKOFF_TIME;

	public ServerList addServer(URI address, boolean primary) {
		final Server server = new Server(address);
		if (primary) {
			primaryServers.add(server);
		} else {
			secondaryServers.add(server);
		}
		return this;
	}

	public Iterator serverIterator() {
		final Iterator primaryIterator = populateList(primaryServers).iterator();
		final Iterator secondaryIterator = populateList(secondaryServers).iterator();
		return new Iterator() {
			@Override
			public boolean hasNext() {
				return primaryIterator.hasNext() || secondaryIterator.hasNext();
			}

			@Override
			public Server next() {
				return primaryIterator.hasNext() ? primaryIterator.next() : secondaryIterator.next();
			}
		};
	}

	private List populateList(ArrayList servers) {
		final long time = System.currentTimeMillis();
		final List list = servers.stream()
				.filter(server -> server.failTime + failureBackoffTime < time)
				.collect(Collectors.toList());
		Collections.shuffle(list);
		return list;
	}

	static class Server {
		private final URI address;
		private volatile long failTime;

		Server(URI address) {
			this.address = address;
		}

		public URI getAddress() {
			return address;
		}

		public void connectionFailed() {
			failTime = System.currentTimeMillis();
		}
	}

}