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/**
 * This interface provides storing and fetching remote log segment metadata with strongly consistent semantics.
 *
 * When {@link #configure(Map)} is invoked on this instance, {@link #BROKER_ID}, {@link #CLUSTER_ID} properties are
 * passed which can be used by this instance if needed. These props can be used if there is a single storage used for
 * different clusters. For ex: MySQL storage can be used as metadata store for all the clusters across the org.
 *
 * todo-tier cleanup the abstractions in this interface.
 */
@InterfaceStability.Unstable
public interface RemoteLogMetadataManager extends Configurable, Closeable {

    /**
     *
     */
    String BROKER_ID = "broker.id";

    /**
     *
     */
    String CLUSTER_ID = "cluster.id";

    /**
     * Stores RemoteLogSegmentMetadata with the given RemoteLogSegmentId.
     *
     * @param remoteLogSegmentMetadata
     * @throws IOException
     */
    void putRemoteLogSegmentData(RemoteLogSegmentMetadata remoteLogSegmentMetadata) throws IOException;

    /**
     * Fetches RemoteLogSegmentId for the given topic partition which contains the given offset.
     *
     * @param topicPartition
     * @param offset
     * @return
     * @throws IOException
     */
    RemoteLogSegmentId getRemoteLogSegmentId(TopicPartition topicPartition, long offset) throws IOException;

    /**
     * Fetches RemoteLogSegmentMetadata for the given RemoteLogSegmentId.
     *
     * @param remoteLogSegmentId
     * @return
     * @throws IOException
     */
    RemoteLogSegmentMetadata getRemoteLogSegmentMetadata(RemoteLogSegmentId remoteLogSegmentId) throws IOException;

    /**
     * Earliest log offset if exists for the given topic partition in the remote storage. Return {@link Optional#empty()}
     * if there are no segments in the remote storage.
     *
     * @param tp
     * @return
     */
    Optional<Long> earliestLogOffset(TopicPartition tp) throws IOException;

    /**
     *
     * @param tp
     * @return
     * @throws IOException
     */
    Optional<Long> highestLogOffset(TopicPartition tp) throws IOException;

    /**
     * Deletes the log segment metadata for the given remoteLogSegmentId.
     *
     * @param remoteLogSegmentId
     * @throws IOException
     */
    void deleteRemoteLogSegmentMetadata(RemoteLogSegmentId remoteLogSegmentId) throws IOException;

    /**
     * List the remote log segment files of the given topicPartition.
     * The RemoteLogManager of a follower uses this method to find out the remote data for the given topic partition.
     *
     * @return List of remote segments, sorted by baseOffset in ascending order.
     */
    default List<RemoteLogSegmentMetadata> listRemoteLogSegments(TopicPartition topicPartition) {
        return listRemoteLogSegments(topicPartition, 0);
    }

    /**
     * @param topicPartition
     * @param minOffset
     * @return List of remote segments, sorted by baseOffset in ascending order.
     */
    List<RemoteLogSegmentMetadata> listRemoteLogSegments(TopicPartition topicPartition, long minOffset);

    /**
     * This method is invoked only when there are changes in leadership of the topic partitions that this broker is
     * responsible for.
     *
     * @param leaderPartitions   partitions that have become leaders on this broker.
     * @param followerPartitions partitions that have become followers on this broker.
     */
    void onPartitionLeadershipChanges(Set<TopicPartition> leaderPartitions, Set<TopicPartition> followerPartitions);

    /**
     * This method is invoked only when the given topic partitions are stopped on this broker. This can happen when a
     * partition is emigrated to other broker or a partition is deleted.
     *
     * @param partitions
     */
    void onStopPartitions(Set<TopicPartition> partitions);

    /**
     * Callback to receive once server is started so that this class can run tasks which should be run only when the
     * server is started.
     */
    void onServerStarted(final String serverEndpoint);
}



/**
 * Metadata about the log segment stored in remote tier storage.
 * todo This can be optimized more, like taking delta as int for computing endOffset by using startOffset and delta and may be few others.  
 */
public class RemoteLogSegmentMetadata implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * Universally unique remote log segment id.
     */
    private final RemoteLogSegmentId remoteLogSegmentId;

    /**
     * Start offset of this segment.
     */
    private final long startOffset;

    /**
     * End offset of this segment.
     */
    private final long endOffset;

    /**
     * Leader epoch of the broker.
     */
    private final int leaderEpoch;

    /**
     * Maximum timestamp in the segment
     */
    private final long maxTimestamp;

    /**
     * Epoch time at which the remote log segment is copied to the remote tier storage.
     */
    private long createdTimestamp;

    /**
     * Size of the segment in bytes.
     */
    private long segmentSizeInBytes;

    /**
     * It indicates that this is marked for deletion.
     */
    private boolean markedForDeletion;

    /**
     * Any context returned by {@link RemoteStorageManager#copyLogSegment(RemoteLogSegmentId, LogSegmentData)} for
     * the given remoteLogSegmentId
     */
    private final byte[] remoteLogSegmentContext;


    /**
     * @param remoteLogSegmentId      Universally unique remote log segment id.
     * @param startOffset             Start offset of this segment.
     * @param endOffset               End offset of this segment.
     * @param maxTimestamp            maximum timestamp in this segment
     * @param leaderEpoch             Leader epoch of the broker.
     * @param createdTimestamp        Epoch time at which the remote log segment is copied to the remote tier storage.
     * @param markedForDeletion       The respective segment of remoteLogSegmentId is marked fro deletion.
     * @param remoteLogSegmentContext Any context returned by {@link RemoteStorageManager#copyLogSegment(RemoteLogSegmentId, LogSegmentData)}
     * @param segmentSizeInBytes      size of this segment in bytes.
     */
    public RemoteLogSegmentMetadata(RemoteLogSegmentId remoteLogSegmentId, long startOffset, long endOffset,
                                    long maxTimestamp, int leaderEpoch, long createdTimestamp,
                                    boolean markedForDeletion, byte[] remoteLogSegmentContext, long segmentSizeInBytes) {
        this.remoteLogSegmentId = remoteLogSegmentId;
        this.startOffset = startOffset;
        this.endOffset = endOffset;
        this.leaderEpoch = leaderEpoch;
        this.maxTimestamp = maxTimestamp;
        this.createdTimestamp = createdTimestamp;
        this.markedForDeletion = markedForDeletion;
        this.remoteLogSegmentContext = remoteLogSegmentContext;
        this.segmentSizeInBytes = segmentSizeInBytes;
    }

...
}