com.vmware.photon.controller.common.zookeeper.ServiceNodeUtils.java Source code

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Here is the source code for com.vmware.photon.controller.common.zookeeper.ServiceNodeUtils.java

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/*
 * Copyright 2015 VMware, Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License.  You may obtain a copy of
 * the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed
 * under the License is distributed on an "AS IS" BASIS, without warranties or
 * conditions of any kind, EITHER EXPRESS OR IMPLIED.  See the License for the
 * specific language governing permissions and limitations under the License.
 */

package com.vmware.photon.controller.common.zookeeper;

import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Class providing static helper methods for {@link ServiceNode}.
 */
public class ServiceNodeUtils {

    private static final Logger logger = LoggerFactory.getLogger(ServiceNodeUtils.class);

    public static void joinService(final ServiceNode serviceNode, final long retryIntervalMilliSeconds) {
        joinService(serviceNode, retryIntervalMilliSeconds, null);
    }

    public static void joinService(final ServiceNode serviceNode, final long retryIntervalMsec,
            final ServiceNodeEventHandler serviceNodeEventHandler) {
        Futures.addCallback(serviceNode.join(), new FutureCallback<ServiceNode.Lease>() {
            @Override
            public void onSuccess(ServiceNode.Lease result) {
                if (serviceNodeEventHandler != null) {
                    serviceNodeEventHandler.onJoin();
                }
                handleLeaseExpiration(result, serviceNode, retryIntervalMsec, serviceNodeEventHandler);
            }

            @Override
            public void onFailure(Throwable t) {
                // This could happen when connection to ZK goes away while we were trying to join the service.
                // The proper way to proceed seems to be to just try to join again, rather than exit the process.
                logger.error("Could not acquire service lease", t);
                logger.debug("Sleeping for {} before retrying", retryIntervalMsec);
                try {
                    Thread.sleep(retryIntervalMsec);
                } catch (InterruptedException e) {
                    logger.error("Failed to sleep between registration retries", e);
                }
                joinService(serviceNode, retryIntervalMsec, serviceNodeEventHandler);
            }
        });
    }

    private static void handleLeaseExpiration(ServiceNode.Lease lease, final ServiceNode serviceNode,
            final long retryIntervalMsec, final ServiceNodeEventHandler serviceNodeEventHandler) {
        Futures.addCallback(lease.getExpirationFuture(), new FutureCallback<Void>() {
            @Override
            public void onSuccess(Void result) {
                rejoin();
            }

            @Override
            public void onFailure(Throwable t) {
                // Could happen if the expiration future gets cancelled: in that case
                // we can't reliably detect when we need to expire the connection anymore,
                // so it probably makes sense to leave and attempt to re-join immediately.
                logger.error("The expiration future has failed", t);
                rejoin();
            }

            public void rejoin() {
                if (serviceNodeEventHandler != null) {
                    serviceNodeEventHandler.onLeave();
                }
                joinService(serviceNode, retryIntervalMsec, serviceNodeEventHandler);
            }
        });
    }
}