Support rsm read

client/client.cpp

@@ -42,6 +42,7 @@ TVoidTask Client(TPoller& poller, TSocket socket) {
 
     TLine line;
     TCommandRequest header;
+    header.Flags = TCommandRequest::EWrite;
     header.Type = static_cast<uint32_t>(TCommandRequest::MessageType);
     auto lineReader = TLineReader(input, 2*1024);
     auto byteWriter = TByteWriter(socket);

examples/kv.cpp

@@ -18,7 +18,7 @@ struct TResultValue: public TCommandResponse {
     char Data[0];
 };
 
-TMessageHolder<TMessage> TKv::Read(TMessageHolder<TCommandRequest> message) {
+TMessageHolder<TMessage> TKv::Read(TMessageHolder<TCommandRequest> message, uint64_t index) {
     auto readKv = message.Cast<TReadKv>();
     std::string_view k(readKv->Data, readKv->KeySize);
     auto it = H.find(std::string(k));

examples/kv.h

@@ -7,7 +7,7 @@
 
 class TKv: public IRsm {
 public:
-    TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message) override;
+    TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message, uint64_t index) override;
     void Write(TMessageHolder<TLogEntry> message) override;
     TMessageHolder<TLogEntry> Prepare(TMessageHolder<TCommandRequest> message, uint64_t term) override;
 

src/messages.h

@@ -82,10 +82,15 @@ static_assert(sizeof(TAppendEntriesResponse) == sizeof(TMessageEx) + 16);
 
 struct TCommandRequest: public TMessage {
     static constexpr EMessageType MessageType = EMessageType::COMMAND_REQUEST;
+    enum EFlags {
+        ENone = 0,
+        EWrite = 1,
+    };
+    uint32_t Flags = ENone;
     char Data[0];
 };
 
-static_assert(sizeof(TCommandRequest) == sizeof(TMessage));
+static_assert(sizeof(TCommandRequest) == sizeof(TMessage) + 4);
 
 struct TCommandResponse: public TMessage {
     static constexpr EMessageType MessageType = EMessageType::COMMAND_RESPONSE;

src/raft.cpp

@@ -24,9 +24,9 @@ static uint32_t rand_(uint32_t* seed) {
 
 } // namespace
 
-TMessageHolder<TMessage> TDummyRsm::Read(TMessageHolder<TCommandRequest> message)
+TMessageHolder<TMessage> TDummyRsm::Read(TMessageHolder<TCommandRequest> message, uint64_t index)
 {
-    return {};
+    return NewHoldedMessage<TCommandResponse>(TCommandResponse {.Index = index});
 }
 
 void TDummyRsm::Write(TMessageHolder<TLogEntry> message)
@@ -253,12 +253,13 @@ void TRaft::OnAppendEntries(TMessageHolder<TAppendEntriesResponse> message) {
 
 void TRaft::OnCommandRequest(TMessageHolder<TCommandRequest> command, const std::shared_ptr<INode>& replyTo) {
     auto& log = State->Log;
-    auto entry = Rsm->Prepare(std::move(command), State->CurrentTerm);
-    log.emplace_back(std::move(entry));
+    if (command->Flags & TCommandRequest::EWrite) {
+        auto entry = Rsm->Prepare(std::move(command), State->CurrentTerm);
+        log.emplace_back(std::move(entry));
+    }
     auto index = log.size();
     if (replyTo) {
-        auto mes = NewHoldedMessage(TCommandResponse {.Index = index});
-        waiting.emplace(TWaiting{mes->Index, mes, replyTo});
+        waiting.emplace(TWaiting{index, std::move(command), replyTo});
     }
 }
 
@@ -378,7 +379,13 @@ void TRaft::ProcessWaiting() {
     auto lastApplied = VolatileState->LastApplied;
     while (!waiting.empty() && waiting.top().Index <= lastApplied) {
         auto w = waiting.top(); waiting.pop();
-        w.ReplyTo->Send(std::move(w.Message));
+        TMessageHolder<TMessage> reply;
+        if (w.Command->Flags & TCommandRequest::EWrite) {
+            reply = NewHoldedMessage(TCommandResponse {.Index = w.Index});
+        } else {
+            reply = Rsm->Read(std::move(w.Command), w.Index);
+        }
+        w.ReplyTo->Send(std::move(reply));
     }
 }
 

src/raft.h

@@ -20,13 +20,13 @@ struct INode {
 // CommandRequest -> Read? -> CurrentIndex (fixate) >= CommittedIndex -> CommandResponse
 struct IRsm {
     virtual ~IRsm() = default;
-    virtual TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message) = 0;
+    virtual TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message, uint64_t index) = 0;
     virtual void Write(TMessageHolder<TLogEntry> message) = 0;
     virtual TMessageHolder<TLogEntry> Prepare(TMessageHolder<TCommandRequest> message, uint64_t term) = 0;
 };
 
 struct TDummyRsm: public IRsm {
-    TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message) override;
+    TMessageHolder<TMessage> Read(TMessageHolder<TCommandRequest> message, uint64_t index) override;
     void Write(TMessageHolder<TLogEntry> message) override;
     TMessageHolder<TLogEntry> Prepare(TMessageHolder<TCommandRequest> message, uint64_t term) override;
 };
@@ -158,7 +158,7 @@ class TRaft {
 
     struct TWaiting {
         uint64_t Index;
-        TMessageHolder<TMessage> Message;
+        TMessageHolder<TCommandRequest> Command;
         std::shared_ptr<INode> ReplyTo;
         bool operator< (const TWaiting& other) const {
             return Index > other.Index;