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JGroups RAFT implementation
There is a newer version: 1.0.14.Final
package org.jgroups.protocols.raft;

import org.jgroups.Address;
import org.jgroups.Global;
import org.jgroups.Header;
import org.jgroups.util.Bits;
import org.jgroups.util.Util;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.function.Supplier;

/**
 * Used to send AppendEntries messages to cluster members. The log entries are contained in actual payload of the message,
 * not in this header.
 * @author Bela Ban
 * @since  0.1
 */
public class AppendEntriesRequest extends RaftHeader {
    protected Address    leader;         // probably not needed as msg.src() contains the leader's address already
    protected int        prev_log_index;
    protected int        prev_log_term;
    protected int        entry_term;     // term of the given entry, e.g. when relaying a log to a late joiner
    protected int        leader_commit;  // the commit_index of the leader
    protected boolean    internal;

    public AppendEntriesRequest() {}
    public AppendEntriesRequest(int term, Address leader, int prev_log_index, int prev_log_term, int entry_term,
                                int leader_commit, boolean internal) {
        super(term);
        this.leader=leader;
        this.prev_log_index=prev_log_index;
        this.prev_log_term=prev_log_term;
        this.entry_term=entry_term;
        this.leader_commit=leader_commit;
        this.internal=internal;
    }

    public short getMagicId() {
        return RAFT.APPEND_ENTRIES_REQ;
    }

    public Supplier create() {
        return AppendEntriesRequest::new;
    }

    @Override
    public int serializedSize() {
        return super.serializedSize() + Util.size(leader) + Bits.size(prev_log_index) + Bits.size(prev_log_term) +
          Bits.size(entry_term) + Bits.size(leader_commit) + Global.BYTE_SIZE;
    }

    @Override
    public void writeTo(DataOutput out) throws IOException {
        super.writeTo(out);
        Util.writeAddress(leader, out);
        Bits.writeInt(prev_log_index, out);
        Bits.writeInt(prev_log_term, out);
        Bits.writeInt(entry_term, out);
        Bits.writeInt(leader_commit, out);
        out.writeBoolean(internal);
    }

    @Override
    public void readFrom(DataInput in) throws IOException, ClassNotFoundException {
        super.readFrom(in);
        leader=Util.readAddress(in);
        prev_log_index=Bits.readInt(in);
        prev_log_term=Bits.readInt(in);
        entry_term=Bits.readInt(in);
        leader_commit=Bits.readInt(in);
        internal=in.readBoolean();
    }

    @Override public String toString() {
        return super.toString() + ", leader=" + leader + ", prev_log_index=" + prev_log_index +
          ", prev_log_term=" + prev_log_term + ", entry_term=" + entry_term + ", leader_commit=" + leader_commit +
          ", internal=" + internal;
    }
}