private void fillMetaPeers(final RaftOutter.EntryMeta.Builder emb, final LogEntry entry) {
        for (final PeerId peer : entry.getPeers()) {
            emb.addPeers(peer.toString());
        }
        if (entry.getOldPeers() != null) {
            for (final PeerId peer : entry.getOldPeers()) {
                emb.addOldPeers(peer.toString());
            }
        }
        if (entry.getLearners() != null) {
            for (final PeerId peer : entry.getLearners()) {
                emb.addLearners(peer.toString());
            }
        }
        if (entry.getOldLearners() != null) {
            for (final PeerId peer : entry.getOldLearners()) {
                emb.addOldLearners(peer.toString());
            }
        }
    }
Send probe or heartbeat request
@param isHeartbeat      if current entries is heartbeat
@param heartBeatClosure heartbeat callback
jraft-core/src/main/java/com/alipay/sofa/jraft/core/Replicator.java