com.linkedin.parseq.zk.client.ZKUtil.java Source code

Introduction

Here is the source code for com.linkedin.parseq.zk.client.ZKUtil.java

Source

/*
 * Copyright 2016 LinkedIn Crop.
 *
 * 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.linkedin.parseq.zk.client;

import java.util.List;
import java.util.stream.Collectors;
import org.apache.zookeeper.KeeperException;

/**
 * @author Ang Xu
 */
public final class ZKUtil {

    private ZKUtil() {
    }

    public static String normalizeZKPath(String basePath, String child) {
        // normalization
        while (basePath.endsWith("/")) {
            basePath = basePath.substring(0, basePath.length() - 2);
        }
        while (child.startsWith("/")) {
            child = child.substring(1);
        }
        return basePath + "/" + child;
    }

    /**
     * Decides whether the given {@link Throwable throwable} is recoverable or not.
     * Recoverable exceptions are defined as such:
     * http://wiki.apache.org/hadoop/ZooKeeper/ErrorHandling
     *
     * @param t the {@link Throwable}
     * @return  {@code true} if {@code t} is recoverable and {@code false} otherwise.
     */
    public static boolean isRecoverable(Throwable t) {
        if (t instanceof KeeperException) {
            KeeperException ex = (KeeperException) t;
            if (ex.code() == KeeperException.Code.CONNECTIONLOSS
                    || ex.code() == KeeperException.Code.OPERATIONTIMEOUT) {
                return true;
            }
        }
        return false;
    }

    public static String findNodeWithUUID(List<String> children, String uuid) {
        for (String child : children) {
            if (child.startsWith(uuid)) {
                return child;
            }
        }
        return null;
    }

    /**
     * Finds node with next lowest sequence number than the given node within
     * the given list of nodes.
     *
     * @param children list of children
     * @param node the given node to compare sequence number with
     * @return the node with next lowest sequence number
     */
    public static String findNodeWithNextLowestSN(List<String> children, String node) {
        List<String> sortedChildren = children.stream()
                .sorted((String o1, String o2) -> Long.compare(getSequenceNumber(o1), getSequenceNumber(o2)))
                .collect(Collectors.toList());

        int index = sortedChildren.indexOf(node);
        if (index > 0) {
            return sortedChildren.get(index - 1);
        } else if (index == 0) {
            return node;
        } else {
            return null;
        }
    }

    /**
     * Gets 10 digit sequence number from the given znode per:
     * http://zookeeper.apache.org/doc/trunk/zookeeperProgrammers.html#Sequence+Nodes+--+Unique+Naming
     */
    private static long getSequenceNumber(String node) {
        final int length = node.length();
        try {
            String seqNumStr = node.substring(length - 10, length);
            return Long.valueOf(seqNumStr);
        } catch (IndexOutOfBoundsException | NumberFormatException ex) {
            throw new IllegalArgumentException(String.format("znode %s doesn't have sequence number", node));
        }
    }
}