Add basic GET command for both mc and redis

server/conn_context.cc

@@ -12,4 +12,8 @@ ConnectionContext::ConnectionContext(::io::Sink* stream, Connection* owner)
     : ReplyBuilder(owner->protocol(), stream), owner_(owner) {
 }
 
+Protocol ConnectionContext::protocol() const {
+  return owner_->protocol();
+}
+
 }  // namespace dfly

server/conn_context.h

@@ -24,6 +24,8 @@ class ConnectionContext : public ReplyBuilder {
     return owner_;
   }
 
+  Protocol protocol() const;
+
  private:
   Connection* owner_;
 };

server/main_service.cc

@@ -146,6 +146,9 @@ void Service::DispatchMC(const MemcacheParser::Command& cmd, std::string_view va
       strcpy(cmd_name, "SET");
       strcpy(set_opt, "NX");
       break;
+    case MemcacheParser::GET:
+      strcpy(cmd_name, "GET");
+      break;
     default:
       cntx->SendMCClientError("bad command line format");
       return;
@@ -168,7 +171,6 @@ void Service::DispatchMC(const MemcacheParser::Command& cmd, std::string_view va
   DispatchCommand(arg_list, cntx);
 }
 
-
 void Service::RegisterHttp(HttpListenerBase* listener) {
   CHECK_NOTNULL(listener);
 }
@@ -191,8 +193,8 @@ void Service::Ping(CmdArgList args, ConnectionContext* cntx) {
 void Service::Set(CmdArgList args, ConnectionContext* cntx) {
   set_qps.Inc();
 
-  std::string_view key = ArgS(args, 1);
+  string_view key = ArgS(args, 1);
-  std::string_view val = ArgS(args, 2);
+  string_view val = ArgS(args, 2);
   VLOG(2) << "Set " << key << " " << val;
 
   ShardId sid = Shard(key, shard_count());
@@ -205,6 +207,29 @@ void Service::Set(CmdArgList args, ConnectionContext* cntx) {
   cntx->SendStored();
 }
 
+void Service::Get(CmdArgList args, ConnectionContext* cntx) {
+  string_view key = ArgS(args, 1);
+  ShardId sid = Shard(key, shard_count());
+
+  OpResult<string> opres;
+
+  shard_set_.Await(sid, [&] {
+    EngineShard* es = EngineShard::tlocal();
+    OpResult<DbSlice::MainIterator> res = es->db_slice.Find(0, key);
+    if (res) {
+      opres.value() = res.value()->second;
+    } else {
+      opres = res.status();
+    }
+  });
+
+  if (opres) {
+    cntx->SendGetReply(key, 0, opres.value());
+  } else if (opres.status() == OpStatus::KEY_NOTFOUND) {
+    cntx->SendGetNotFound();
+  }
+  cntx->EndMultilineReply();
+}
 
 VarzValue::Map Service::GetVarzStats() {
   VarzValue::Map res;
@@ -227,7 +252,8 @@ void Service::RegisterCommands() {
   using CI = CommandId;
 
   registry_ << CI{"PING", CO::STALE | CO::FAST, -1, 0, 0, 0}.HFUNC(Ping)
-            << CI{"SET", CO::WRITE | CO::DENYOOM, -3, 1, 1, 1}.HFUNC(Set);
+            << CI{"SET", CO::WRITE | CO::DENYOOM, -3, 1, 1, 1}.HFUNC(Set)
+            << CI{"GET", CO::READONLY | CO::FAST, 2, 1, 1, 1}.HFUNC(Get);
 }
 
 }  // namespace dfly

server/main_service.h

@@ -48,6 +48,7 @@ class Service {
  private:
   void Ping(CmdArgList args, ConnectionContext* cntx);
   void Set(CmdArgList args, ConnectionContext* cntx);
+  void Get(CmdArgList args, ConnectionContext* cntx);
 
   void RegisterCommands();
 

server/reply_builder.cc

@@ -56,7 +56,6 @@ void RespSerializer::SendSimpleString(std::string_view str) {
   Send(v, ABSL_ARRAYSIZE(v));
 }
 
-
 void RespSerializer::SendBulkString(std::string_view str) {
   char tmp[absl::numbers_internal::kFastToBufferSize + 3];
   tmp[0] = '$';  // Format length
@@ -97,7 +96,6 @@ void ReplyBuilder::SendStored() {
   }
 }
 
-
 void ReplyBuilder::SendMCClientError(string_view str) {
   DCHECK(protocol_ == Protocol::MEMCACHE);
 
@@ -105,6 +103,12 @@ void ReplyBuilder::SendMCClientError(string_view str) {
   serializer_->Send(v, ABSL_ARRAYSIZE(v));
 }
 
+void ReplyBuilder::EndMultilineReply() {
+  if (protocol_ == Protocol::MEMCACHE) {
+    serializer_->SendDirect("END\r\n");
+  }
+}
+
 void ReplyBuilder::SendError(string_view str) {
   DCHECK(protocol_ == Protocol::REDIS);
 
@@ -134,4 +138,20 @@ void ReplyBuilder::SendError(OpStatus status) {
   }
 }
 
+void ReplyBuilder::SendGetReply(std::string_view key, uint32_t flags, std::string_view value) {
+  if (protocol_ == Protocol::REDIS) {
+    as_resp()->SendBulkString(value);
+  } else {
+    string first = absl::StrCat("VALUE ", key, " ", flags, " ", value.size(), "\r\n");
+    iovec v[] = {IoVec(first), IoVec(value), IoVec(kCRLF)};
+    serializer_->Send(v, ABSL_ARRAYSIZE(v));
+  }
+}
+
+void ReplyBuilder::SendGetNotFound() {
+  if (protocol_ == Protocol::REDIS) {
+    as_resp()->SendNull();
+  }
+}
+
 }  // namespace dfly

server/reply_builder.h

@@ -76,6 +76,7 @@ class ReplyBuilder {
   }
 
   void SendMCClientError(std::string_view str);
+  void EndMultilineReply();
 
   void SendSimpleRespString(std::string_view str) {
     as_resp()->SendSimpleString(str);
@@ -84,6 +85,10 @@ class ReplyBuilder {
   void SendRespBlob(std::string_view str) {
     as_resp()->SendDirect(str);
   }
+
+  void SendGetReply(std::string_view key, uint32_t flags, std::string_view value);
+  void SendGetNotFound();
+
  private:
   RespSerializer* as_resp() {
     return static_cast<RespSerializer*>(serializer_.get());