Too many read mmp in send !!!!

[Cczzzz]

Send once and take multiple times mmp.
For example ，in commit
DLedgerMmapFileStore#updateCommittedIndex updateCommittedIndex

    DLedgerEntry dLedgerEntry = get(newCommittedIndex);
    PreConditions.check(dLedgerEntry != null, DLedgerResponseCode.DISK_ERROR);
    this.committedIndex = newCommittedIndex;
    this.committedPos = dLedgerEntry.getPos() + dLedgerEntry.getSize();

just want know pos and size.but in get()

       indexSbr = indexFileList.getData(index * INDEX_UNIT_SIZE, INDEX_UNIT_SIZE);
        PreConditions.check(indexSbr != null && indexSbr.getByteBuffer() != null, DLedgerResponseCode.DISK_ERROR, "Get null index for %d", index);
        indexSbr.getByteBuffer().getInt(); //magic
        long pos = indexSbr.getByteBuffer().getLong();
        int size = indexSbr.getByteBuffer().getInt();
        dataSbr = dataFileList.getData(pos, size);
        PreConditions.check(dataSbr != null && dataSbr.getByteBuffer() != null, DLedgerResponseCode.DISK_ERROR, "Get null data for %d", index);
        DLedgerEntry dLedgerEntry = DLedgerEntryCoder.decode(dataSbr.getByteBuffer());
        PreConditions.check(pos == dLedgerEntry.getPos(), DLedgerResponseCode.DISK_ERROR, "%d != %d", pos, dLedgerEntry.getPos());

indexFileList have already known pos and size.Have to read dataFileList and
DLedgerEntryCoder.decode？decode？ Is this necessary？

In my test ，dLedger is very poor performance !!!!

[Cczzzz]

And why in doAppend need call dLedgerStore.updateCommittedIndex().Is not call in commit command？

   private void handleDoAppend(long writeIndex, PushEntryRequest request,
        CompletableFuture<PushEntryResponse> future) {
        try {
            PreConditions.check(writeIndex == request.getEntry().getIndex(), DLedgerResponseCode.INCONSISTENT_STATE);
            DLedgerEntry entry = dLedgerStore.appendAsFollower(request.getEntry(), request.getTerm(), request.getLeaderId());
            PreConditions.check(entry.getIndex() == writeIndex, DLedgerResponseCode.INCONSISTENT_STATE);
            future.complete(buildResponse(request, DLedgerResponseCode.SUCCESS.getCode()));
            dLedgerStore.updateCommittedIndex(request.getTerm(), request.getCommitIndex());
        } catch (Throwable t) {
            logger.error("[HandleDoWrite] writeIndex={}", writeIndex, t);
            future.complete(buildResponse(request, DLedgerResponseCode.INCONSISTENT_STATE.getCode()));
        }
    }

[Cczzzz]

Can modify process append and commit In two different threads。

[Cczzzz]

Can modify process append and commit In two different threads。

I see ，dledger No state machine ，so append = commit

[Cczzzz]

Can modify process append and commit In two different threads。

I see ，dledger No state machine ，so append = commit

just send a null commit when too much behind

[Cczzzz]

#98