distributedlog-core/src/main/java/org/apache/distributedlog/metadata/LogMetadataForReader.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.distributedlog.metadata;

import com.google.common.base.Optional;

import java.net.URI;

/**
 * Log Metadata for Reader.
 */
public class LogMetadataForReader extends LogMetadata {

    /**
     * Get the root path to store subscription infos of a log.
     *
     * @param uri
     *          namespace of the log
     * @param logName
     *          name of the log
     * @param logIdentifier
     *          identifier of the log
     * @return subscribers root path
     */
    public static String getSubscribersPath(URI uri, String logName, String logIdentifier) {
        return getLogComponentPath(uri, logName, logIdentifier, SUBSCRIBERS_PATH);
    }

    /**
     * Get the path that stores subscription info for a <code>subscriberId</code> for a <code>log</code>.
     *
     * @param uri
     *          namespace of the log
     * @param logName
     *          name of the log
     * @param logIdentifier
     *          identifier of the log
     * @param subscriberId
     *          subscriber id of the log
     * @return subscriber's path
     */
    public static String getSubscriberPath(URI uri, String logName, String logIdentifier, String subscriberId) {
        return String.format("%s/%s", getSubscribersPath(uri, logName, logIdentifier), subscriberId);
    }

    /**
     * Create a metadata representation of a log for reader.
     *
     * @param uri
     *          namespace to store the log
     * @param logName
     *          name of the log
     * @param logIdentifier
     *          identifier of the log
     * @return metadata representation of a log for reader
     */
    public static LogMetadataForReader of(URI uri, String logName, String logIdentifier) {
        return new LogMetadataForReader(uri, logName, logIdentifier);
    }

    static final  String SUBSCRIBERS_PATH = "/subscribers";

    /**
     * metadata representation of a log.
     *
     * @param uri           namespace to store the log
     * @param logName       name of the log
     * @param logIdentifier identifier of the log
     */
    private LogMetadataForReader(URI uri, String logName, String logIdentifier) {
        super(uri, logName, logIdentifier);
    }

    /**
     * Get the readlock path for the log or a subscriber of the log.
     *
     * @param subscriberId
     *          subscriber id. it is optional.
     * @return read lock path
     */
    public String getReadLockPath(Optional<String> subscriberId) {
        if (subscriberId.isPresent()) {
            return logRootPath + SUBSCRIBERS_PATH + "/" + subscriberId.get() + READ_LOCK_PATH;
        } else {
            return logRootPath + READ_LOCK_PATH;
        }
    }
}