1 /*
2 * LogProtocolMessage.h
3 *
4 * This source file is part of the FoundationDB open source project
5 *
6 * Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
7 *
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20
21 #ifndef FDBSERVER_LOGPROTOCOLMESSAGE_H
22 #define FDBSERVER_LOGPROTOCOLMESSAGE_H
23 #pragma once
24
25 #include "fdbclient/FDBTypes.h"
26 #include "fdbclient/CommitTransaction.h"
27
28 template <class Ar, class VersionOptions>
applyVersionStartingHere(Ar & ar,VersionOptions vo)29 typename Ar::READER& applyVersionStartingHere(Ar& ar, VersionOptions vo) {
30 vo.read(ar);
31 return ar;
32 }
33
34 template <class Ar, class VersionOptions>
applyVersionStartingHere(Ar & ar,VersionOptions vo)35 typename Ar::WRITER& applyVersionStartingHere(Ar& ar, VersionOptions vo) {
36 vo.write(ar);
37 return ar;
38 }
39
40 struct LogProtocolMessage {
41 // This message is pushed into the log system tag for each storage server to inform it what protocol version
42 // should be used to deserialize subsequent MutationRefs.
43
44 // It's legitimate to add extra information here (using the protocol version for backward compatibility) but
45 // currently there is none.
46
47 // This mechanism passes various ASSERTs in simulation, but has never been used in anger (because MutationRef's
48 // serialization format has never changed) so think about testing when it does change.
49
50 // Storage servers merging these messages with MutationRefs need to distinguish the two, so the first byte of
51 // the serialization of this message is a type code which is reserved in the MutationRef::Type enum and will thus
52 // never be the first byte of a MutationRef message.
53
LogProtocolMessageLogProtocolMessage54 LogProtocolMessage() {}
55
toStringLogProtocolMessage56 std::string toString() const {
57 return format("code: %d", MutationRef::Reserved_For_LogProtocolMessage);
58 }
59
60 template <class Ar>
serializeLogProtocolMessage61 void serialize(Ar& ar) {
62 uint8_t poly = MutationRef::Reserved_For_LogProtocolMessage;
63 serializer(ar, poly);
64 applyVersionStartingHere(ar, IncludeVersion());
65 }
66
startsLogProtocolMessageLogProtocolMessage67 static bool startsLogProtocolMessage(uint8_t byte) {
68 return byte == MutationRef::Reserved_For_LogProtocolMessage;
69 }
isNextInLogProtocolMessage70 template <class Ar> static bool isNextIn(Ar& ar) { return startsLogProtocolMessage(*(const uint8_t*)ar.peekBytes(1)); }
71 };
72
73 #endif
74