org.jgroups.protocols.raft.Log Maven / Gradle / Ivy
package org.jgroups.protocols.raft;
import org.jgroups.Address;
import java.io.Closeable;
import java.nio.ByteBuffer;
import java.util.Map;
import java.util.function.ObjLongConsumer;
/**
* The interface for a persistent log. See doc/design/Log.txt for details.
* @author Bela Ban
* @since 0.1
*/
public interface Log extends Closeable {
/** Called after the instance has been created
* @param log_name The name of the log. Implementations can create a DB or file named after this, e.g.
* /tmp/ args) throws Exception;
/**
* Do not cache a change (e.g. AppendEntriesRequest, or setting the commit index), but force a write
* to disk (fsync), if true.
*/
Log useFsync(boolean f);
boolean useFsync();
/** Remove the persistent store, e.g. DB table, or file */
void delete() throws Exception;
/** Returns the current term */
long currentTerm();
/** Sets the current term */
Log currentTerm(long new_term);
/** Returns the address of the candidate that this node voted for in the current term */
Address votedFor();
/** Sets the address of the member this node voted for in the current term. Only invoked once per term */
Log votedFor(Address member);
/** Returns the current commit index. (May get removed as the RAFT paper has this as in-memory attribute) */
long commitIndex();
/**
* Sets commitIndex to a new value
* @param new_index The new index to set commitIndex to. May throw an exception if new_index > lastApplied()
* @return the log
*/
Log commitIndex(long new_index);
/** Returns the index of the first log entry */
long firstAppended();
/** Returns the index of the last append entry
* This value is set by {@link #append(long,LogEntries)} */
long lastAppended();
/**
* Stores a snapshot in the log.
* @param sn The snapshot data
*/
void setSnapshot(ByteBuffer sn);
/**
* Gets the snapshot from the log
* @return The snapshot, or null if not existing
*/
ByteBuffer getSnapshot();
/**
* Append the entries starting at index. Advance last_appended by the number of entries appended.
*
* If the operation fails, then last_appended needs to be the index of the last successful append. E.g. if
* last_appended is 1, and we attempt to appened 100 entries, but fail at 51, then last_appended must be 50 (not 1!).
*
* @param index The index at which to append the entries. Should be the same as lastAppended. LastAppended needs
* to be incremented by the number of entries appended
* @param entries The entries to append
* @return long The index of the last appended entry
*/
long append(long index, LogEntries entries);
/**
* Gets the entry at start_index. Updates current_term and last_appended accordingly
* @param index The index
* @return The LogEntry, or null if none is present at index.
*/
LogEntry get(long index);
/**
* Truncates the log up to (and excluding) index. All entries < index are removed. First = index.
* @param index_exclusive If greater than commit_index, commit_index will be used instead
*/
void truncate(long index_exclusive);
/**
* Clears all entries and sets first_appended/last_appended/commit_index to index and appends entry at index. The
* next entry will be appended at last_appended+1.
* Use when a snapshot has been received by a follower, after setting the snapshot, to basically create a new log
* @param index The new index
* @param entry The entry to append
* @throws Exception Thrown if this operation failed
*/
void reinitializeTo(long index, LogEntry entry) throws Exception;
/**
* Delete all entries starting from start_index (including the entry at start_index).
* Updates current_term and last_appended accordingly
*
* @param start_index
*/
void deleteAllEntriesStartingFrom(long start_index);
/**
* Applies function to all elements of the log in range [max(start_index,first_appended) .. min(last_appended,end_index)].
* @param function The function to be applied
* @param start_index The start index. If smaller than first_appended, first_appended will be used
* @param end_index The end index. If greater than last_appended, last_appended will be used
*/
void forEach(ObjLongConsumer function, long start_index, long end_index);
/** Applies a function to all elements in range [first_appended .. last_appended] */
void forEach(ObjLongConsumer function);
/** The number of entries in the log */
default long size() {
long last=lastAppended(), first=firstAppended();
return first == 0? last : last-first+1;
}
long sizeInBytes();
}